AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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comments inside the quote
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318 Engine stumble
- Thread starter glhx
- Start date
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nm9stheham
Well-Known Member
Actually, a .045" gap should improve the spark kernal and that improves overall combustion. I would expect that to be worthwhile.
Agreed on making too many changes at a time. Change distributor and get the spark gap set up and running OK, then go back to the sync and timing.
Agreed on making too many changes at a time. Change distributor and get the spark gap set up and running OK, then go back to the sync and timing.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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No arguement outta me nm9,
but first is the problem of making a proper .045 gap out of a plug that comes with .035. Second is, if the new system can fire it and third is, it's a low-po combo that doesn't absolutely require that amount of pressure. I'm all for trying it later after this stutter is solved. I've been running wide gaps for 40 years or more, but not every coil will fire them and not all the time.
And finally it's just one more variable to undo, if the stutter remains. And I'm pretty sure it will remain. The current ignition is fine as witnessed in the video.
nm9stheham
Well-Known Member
Well, if the ballast is indeed 1.5 ohms then the ignition is not set up right. And looking at the problems of setting the dwell vs points gap described earlier puts some items in doubt, along with some of the pix. I won't guarantee that it will solve the stumble but if the new ignition is fault free (yes, you are right, a new potential variable), then it ought to give a more solid ignition setup and relieve worrying about that aspect of things.
BTW, ignition deficiencies can show up with low comp as well as high comp situations. I can't recall how many times a worn points rubbing block would close the gap and cause low-mid RPM stutters in all sorts of engines.
I found your observation on the fact that the transition slot action should not be observable to be something to think about. I guess we don't know what the OP is actually looking at... the auxiliary venturi's or waaay down at the blades and perhaps seeing the slots? What we need is a way to put our arms and hands and ears and eyes through the internet and be there....
BTW, ignition deficiencies can show up with low comp as well as high comp situations. I can't recall how many times a worn points rubbing block would close the gap and cause low-mid RPM stutters in all sorts of engines.
I found your observation on the fact that the transition slot action should not be observable to be something to think about. I guess we don't know what the OP is actually looking at... the auxiliary venturi's or waaay down at the blades and perhaps seeing the slots? What we need is a way to put our arms and hands and ears and eyes through the internet and be there....
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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I agree
I think that if either of us, or any of several others here, got eyes on those boosters we might almost instantly see the problem. I gave a description of what I would do many posts ago, and I haven't yet seen anything to make me want to change my mind.
I think that if either of us, or any of several others here, got eyes on those boosters we might almost instantly see the problem. I gave a description of what I would do many posts ago, and I haven't yet seen anything to make me want to change my mind.
glhx
Well-Known Member
I know it’s been a while.
To update this some. I have not had a lot of time to work on the car.
I did change the distributor to the skip white gym hei style distributor.
I set the base timing to 16°.
The spark is much hotter and the vacuum advance is operational where the points distributor advance was frozen. At first the car still had the hesitation but I could drive it.
Now it Revs up fine
I put it in gear.....and....
It dies as soon as I give it any gas. It won’t even move a foot
To update this some. I have not had a lot of time to work on the car.
I did change the distributor to the skip white gym hei style distributor.
I set the base timing to 16°.
The spark is much hotter and the vacuum advance is operational where the points distributor advance was frozen. At first the car still had the hesitation but I could drive it.
Now it Revs up fine
I put it in gear.....and....
It dies as soon as I give it any gas. It won’t even move a foot
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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Some thoughts
1) low fuel level,or
2) non-functional accelerator pump circuit,or
3) lazy transfer circuits,or
4) bad bowl-vent
All but the first one of these can be indicative of a bad T-port sync, usually due to too much idle-timing, but not absolutely necessarily.
> Reset the float level to the high side of the spec.
> Make sure the bowl is vented any time the engine is running.
> The Distributor should be getting it's vacuum signal from the SPARK-PORT. The Vcan should be inoperative at idle with ZERO vacuum measured on the sparkport. If you have a vacuum signal here with a stock or near stock cam, the primary throttle valves are too far open. Find out why.
> The PCV should be working as designed by the factory, and there must not be any vacuum leaks, anywhere.
> the secondary throttle valves should be closed up tight but not sticking.
> The engine temp should be more than 185, less than 205, the higher the better, and dead stable. If the temp is running up and down, something is wrong. You cannot tune the engine with this going on.
Now:
> The transfer port exposure, under the throttle blades, should be square to perhaps a little taller than wide. Make them so. After this is done,Do not change this setting more than 1/2 turn in either direction.(You have to take the carb off and flip it upside down to see this.) Reset the mixture screws as may be necessary.Then, set the idle speed with timing, somewhere between 6 and 16 degrees. Start at the low-end. Go up in two degree increments, until the engine is happy between about 550 and 650 in gear.Like I said; Do not touch the speed screw, more than 1/2 turn+/-, to fine tune. The idle should not jump up more than about 100 rpm when you take it out of gear. If your engine will not do this, something is wrong.
> Reset the pumpshot to begin at the slightest bit of travel of the throttle blades.
> Limit the power-timing to 36* or less, as may be required to stay out of detonation. Don't be in a hurry to bring it all in; if it doesn't come all-in until 3600 that will be fine......... at this time.
If the engine will not idle with the above rig-ma-role worked out, and it has hydraulic lifters, then we will have to take the carb apart.
I hope I thought of everything,lol.
done
1) low fuel level,or
2) non-functional accelerator pump circuit,or
3) lazy transfer circuits,or
4) bad bowl-vent
All but the first one of these can be indicative of a bad T-port sync, usually due to too much idle-timing, but not absolutely necessarily.
> Reset the float level to the high side of the spec.
> Make sure the bowl is vented any time the engine is running.
> The Distributor should be getting it's vacuum signal from the SPARK-PORT. The Vcan should be inoperative at idle with ZERO vacuum measured on the sparkport. If you have a vacuum signal here with a stock or near stock cam, the primary throttle valves are too far open. Find out why.
> The PCV should be working as designed by the factory, and there must not be any vacuum leaks, anywhere.
> the secondary throttle valves should be closed up tight but not sticking.
> The engine temp should be more than 185, less than 205, the higher the better, and dead stable. If the temp is running up and down, something is wrong. You cannot tune the engine with this going on.
Now:
> The transfer port exposure, under the throttle blades, should be square to perhaps a little taller than wide. Make them so. After this is done,Do not change this setting more than 1/2 turn in either direction.(You have to take the carb off and flip it upside down to see this.) Reset the mixture screws as may be necessary.Then, set the idle speed with timing, somewhere between 6 and 16 degrees. Start at the low-end. Go up in two degree increments, until the engine is happy between about 550 and 650 in gear.Like I said; Do not touch the speed screw, more than 1/2 turn+/-, to fine tune. The idle should not jump up more than about 100 rpm when you take it out of gear. If your engine will not do this, something is wrong.
> Reset the pumpshot to begin at the slightest bit of travel of the throttle blades.
> Limit the power-timing to 36* or less, as may be required to stay out of detonation. Don't be in a hurry to bring it all in; if it doesn't come all-in until 3600 that will be fine......... at this time.
If the engine will not idle with the above rig-ma-role worked out, and it has hydraulic lifters, then we will have to take the carb apart.
I hope I thought of everything,lol.
done
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glhx
Well-Known Member
First thing to note ......ive been working on the list you provided until it got dark.
I rechecked the transfer slots and the accelerator pump. The are small squares and the accelerator pump is well adjusted.
The pumps are spraying fuel.....I can’t say the pump cam is the right one right now. The pcv is hooked to the intake manifold into a t line going to the booster.
I will put it back into the carburetor and run a new hose to the booster from the manifold. Right now it is capped off at the intake.
I also put some smoke in the intake with the carb blocked off on the top.
Smoke came out of the choke area. I took the choke off and saw a small round gasket in between the choke housing and the carburetor.
I don’t know why smoke was coming out of the choke area or if it is supposed to do that. I decided the gasket needs to be replaced as it was very thin.
There is some sort of piston in the choke housing. I’m not sure what it does yet. It slides loosely in a cylinder
So the choke is off. And that little port is exposed. I then turned out the idle screws to 2. Car idles fine again and is movable.
The off idle stumble is still there.
I will put the choke back on and start over with the mixture screws. I’m hoping this was the cause of some problems.
The reason I turned out the screws all the way was because I wanted to see if it was too much air or lack of gas. When I have time again I will go through the list and see where that takes this.
I rechecked the transfer slots and the accelerator pump. The are small squares and the accelerator pump is well adjusted.
The pumps are spraying fuel.....I can’t say the pump cam is the right one right now. The pcv is hooked to the intake manifold into a t line going to the booster.
I will put it back into the carburetor and run a new hose to the booster from the manifold. Right now it is capped off at the intake.
I also put some smoke in the intake with the carb blocked off on the top.
Smoke came out of the choke area. I took the choke off and saw a small round gasket in between the choke housing and the carburetor.
I don’t know why smoke was coming out of the choke area or if it is supposed to do that. I decided the gasket needs to be replaced as it was very thin.
There is some sort of piston in the choke housing. I’m not sure what it does yet. It slides loosely in a cylinder
So the choke is off. And that little port is exposed. I then turned out the idle screws to 2. Car idles fine again and is movable.
The off idle stumble is still there.
I will put the choke back on and start over with the mixture screws. I’m hoping this was the cause of some problems.
The reason I turned out the screws all the way was because I wanted to see if it was too much air or lack of gas. When I have time again I will go through the list and see where that takes this.
nm9stheham
Well-Known Member
The small piston in the cylinder in the choke assembly sounds like the choke pull-off for a Holley electric choke. It is there so that if you drive the car while the choke is still active, and if you open the throttle a medium or large amount, this pull-off mechanism will open the choke plate to let more air in.... i.e. it 'pulls off' the choke for that situation.
It should be activated by a vacuum port above the primary throttle plate, similar to the ported vacuum going to the distributor advance. (You can see the tiny port on the back of the electric choke assembly at 1:18 into this video; look at the small hole surrounded by brass.)
So smoke going from the carb body into the choke pull-off area should be OK but there should be some seal between choke and carb body so the pull-off can actually work.
Why this seems to be effecting the engine's operation is a mystery to me. This should go to a small port above the throttle plates, and if the choke is removed and exposed that small port, then that should dump some extra air into the carb above the throttle plates. It would normally only effect operation if the choke is closed too much. Is the choke plate opened or partly closed when you have the problem? And if the choke mechanism is now removed and the choke plate is flapping loose, is it closed or open when you get better engine operation?
Some general question on your choke setting and operation:
One note on the secondary stop screws: the t-port exposure being a square hole is a good starting point, but you should be ready to adjust it from there. Having to close the secondary throttles some more for that stock 318 engine would not surprise me. It is a smaller engine and the stock cam does not need to pull in as much air, so having the secondary plates open a bit may dump too much air into the intake manifold. As an example, with a 340 and a moderate cam, we still had to close the secondary plates so that the exposed slot was smaller than a square by adjusting the stop screw.
And one final note: Does you PCV valve work properly? Remove it so that the end of the PCV valve that goes into the valve cover is exposed but the PCV valve is still hooked to the hose going to the base of the carb. Now listen to the open end of the PCV valve at idle; you should hear very little air flow into the PCV valve at idle. If you hear a loud whoooosh of air into the PCV valveat idle then it is stuck open and letting a lot of extra air into the intake manifold. Now put your finger on the open end of the PCV valve; the idle should not change or change very little. If it does change a lot, then the PCV valve is not good.
Do you have a vacuum gauge? If not, then you should get one and use it to see tell us the intake manifold vacuum at idle.
It should be activated by a vacuum port above the primary throttle plate, similar to the ported vacuum going to the distributor advance. (You can see the tiny port on the back of the electric choke assembly at 1:18 into this video; look at the small hole surrounded by brass.)
So smoke going from the carb body into the choke pull-off area should be OK but there should be some seal between choke and carb body so the pull-off can actually work.
Why this seems to be effecting the engine's operation is a mystery to me. This should go to a small port above the throttle plates, and if the choke is removed and exposed that small port, then that should dump some extra air into the carb above the throttle plates. It would normally only effect operation if the choke is closed too much. Is the choke plate opened or partly closed when you have the problem? And if the choke mechanism is now removed and the choke plate is flapping loose, is it closed or open when you get better engine operation?
Some general question on your choke setting and operation:
- What temperature is it at your location when you start the engine cold?
- Are you pushing the the throttle once to the floor before starting a cold to set the choke?
- If you do this, where does the choke plate close to?
- And is the choke opening after a few minutes?
One note on the secondary stop screws: the t-port exposure being a square hole is a good starting point, but you should be ready to adjust it from there. Having to close the secondary throttles some more for that stock 318 engine would not surprise me. It is a smaller engine and the stock cam does not need to pull in as much air, so having the secondary plates open a bit may dump too much air into the intake manifold. As an example, with a 340 and a moderate cam, we still had to close the secondary plates so that the exposed slot was smaller than a square by adjusting the stop screw.
And one final note: Does you PCV valve work properly? Remove it so that the end of the PCV valve that goes into the valve cover is exposed but the PCV valve is still hooked to the hose going to the base of the carb. Now listen to the open end of the PCV valve at idle; you should hear very little air flow into the PCV valve at idle. If you hear a loud whoooosh of air into the PCV valveat idle then it is stuck open and letting a lot of extra air into the intake manifold. Now put your finger on the open end of the PCV valve; the idle should not change or change very little. If it does change a lot, then the PCV valve is not good.
Do you have a vacuum gauge? If not, then you should get one and use it to see tell us the intake manifold vacuum at idle.
glhx
Well-Known Member
I’ve been working on this lately and have made some headway.
I jetted up to stock Holley specs. Went from 60-64
The lean spot is mostly gone.....
The vaccum is still 20
I’m trying to total time the the car now.
I set it at 36° and had to rev it to 3600 to get that to line up with the 0 mark.
37° and 38° never did line up with the zero mark no matter where I rev it.
Does this mean my total timing is 36° at 3600
This is the gm HEI Skip white distributor. How can I get 36° to come in at 3000
Is there some sort of limiter I can put on the advance plate?
I’m not exactly sure how this works.
To see where the timing was at 3000
I set the timing light to 34° and that was 3000rpm
35° is 3300
So 36 at 3600 is the same as 34 at 3000
What is my total timing?
I jetted up to stock Holley specs. Went from 60-64
The lean spot is mostly gone.....
The vaccum is still 20
I’m trying to total time the the car now.
I set it at 36° and had to rev it to 3600 to get that to line up with the 0 mark.
37° and 38° never did line up with the zero mark no matter where I rev it.
Does this mean my total timing is 36° at 3600
This is the gm HEI Skip white distributor. How can I get 36° to come in at 3000
Is there some sort of limiter I can put on the advance plate?
I’m not exactly sure how this works.
To see where the timing was at 3000
I set the timing light to 34° and that was 3000rpm
35° is 3300
So 36 at 3600 is the same as 34 at 3000
What is my total timing?
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AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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36@3600 is the same as 36* at 3600 and not the same as 36* at any other rpm..... unless the timing lite says so.
With the Vcan removed, check the timing every 400 rpm from 3600 down, namely 3200/2800/2400/2000/1600. Plot those numbers on a graph with rpm along the bottom and advance up the side. Next connect the lowest three dots with a straight line, averaging up the middle. Then the top two get connected. Then extend the lines until they cross or meet. Now you have a pretty good idea of what your timing is from 1600 to 3600.
There is nothing wrong with 36* at 3600 unless it appears on the same graph with less than 10* at 1000rpm. If that appears on your graph, then yes, you will want to reduce the flyweight travel. Then rev it back up to 3600 and twist the D to get 36* again, then check the idle timing. If it is now more than 10* and less than 16* you done good. If you are targeting a specific idle timing, like say 14 but you only have 10, then you will have to limit the flyweight travel some more, and again retest.
With 36*@3000 timing, you may have to run premium gas to keep her out of detonation.I would not be in a hurry to try and run that.
In a streetcar; You will not likely feel the difference from 36* to 34* with your butt dyno. Maybe your butt-dyno will not feel the difference from 32* to 36* either. This is because the vast majority of the time, you will not be at WOT, and will not miss 3 or 4 or 5 horsepower at 3600 rpm. Your right foot will just drive that many horsepower deeper into the throttle. You would have to have a pretty small engine to miss them. After all; 5/150~3.3% at the low end of the scale and just 5/230~2.1% at the higher end.
So sneak up on the power-timing. Don't be afraid to take several days or even weeks. Get to know your engine and the sound of NO-detonation. Then you will hear, and maybe feel, detonation if it comes.
Detonation must be avoided at all costs.
With the Vcan removed, check the timing every 400 rpm from 3600 down, namely 3200/2800/2400/2000/1600. Plot those numbers on a graph with rpm along the bottom and advance up the side. Next connect the lowest three dots with a straight line, averaging up the middle. Then the top two get connected. Then extend the lines until they cross or meet. Now you have a pretty good idea of what your timing is from 1600 to 3600.
There is nothing wrong with 36* at 3600 unless it appears on the same graph with less than 10* at 1000rpm. If that appears on your graph, then yes, you will want to reduce the flyweight travel. Then rev it back up to 3600 and twist the D to get 36* again, then check the idle timing. If it is now more than 10* and less than 16* you done good. If you are targeting a specific idle timing, like say 14 but you only have 10, then you will have to limit the flyweight travel some more, and again retest.
With 36*@3000 timing, you may have to run premium gas to keep her out of detonation.I would not be in a hurry to try and run that.
In a streetcar; You will not likely feel the difference from 36* to 34* with your butt dyno. Maybe your butt-dyno will not feel the difference from 32* to 36* either. This is because the vast majority of the time, you will not be at WOT, and will not miss 3 or 4 or 5 horsepower at 3600 rpm. Your right foot will just drive that many horsepower deeper into the throttle. You would have to have a pretty small engine to miss them. After all; 5/150~3.3% at the low end of the scale and just 5/230~2.1% at the higher end.
So sneak up on the power-timing. Don't be afraid to take several days or even weeks. Get to know your engine and the sound of NO-detonation. Then you will hear, and maybe feel, detonation if it comes.
Detonation must be avoided at all costs.
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glhx
Well-Known Member
Vac advance is unhooked. The advance will be limited after I get the total timing in. What vac advance should I go with? I have the msd limiter. I was planning on 14° Or run it as high as it wants until it pings and then back off.
What I have at idle right now is 13°
I had it at 15° and it seemed fine. The timing went up to 38° and I was told that was too much so I turned it to 36°
The only time it pings is when it’s cold. That’s at idle
Once it warms up it’s fine. The choke is not set up yet. It’s about 65°F here when I was tuning with the choke full open. If I let the car cool back down it pings some after restarting it. .....
When it’s cold it runs lean enough to shut the car down when I hit the accelerator. I’m switching to the orange cam tomorrow and that should help. Pretty sure that’s cam related. I’m not worried about that yet. That’s all in the carburetor I’m pretty sure and it’s just running lean on the idle fuel restrictor. I’m working on adjustable ifr and idle air bleeds and will fine tune that.
I plan to run the cheapest 87 octane gas I can find. This car is not for racing or even spirited driving much. If anything I’m after the best fuel economy I can get. I’m running a stock cam, streetmaster Intake and Holley 600 for that reason.
So.......36° at 3000 I need to run higher octane....if that’s the case I’ll leave it where it is. I won’t be doing wide open pulls or anything like that rite now. If I need to I’ll li it the advance plate. I was looking at how to go about that. I can put a roll pin in it and stop it....then file it down until I get where it needs to be.
If I won’t even notice the difference between 36° @3000 and 36° @ 3600 then I won’t bother. I will be in the main jets and transfer system most of the time.
There isn’t much difference in power? Like 5hp?
I did a loose chart on the way to seeing what the total was. I have some moroso advance springs to tune the curve that are coming in the mail tomorrow. This timing and testing today was strictly to see where it was all in at so I could limit it if I needed to. I wasn’t sure what to expect. If I won’t even feel the difference between 3000 and 3600 street driving it’s fine where it is.
I’ll do a better more accurate chart that’s more planned out.what do I want this chart to looks like?
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AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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That's a nice starter curve. I like the kink for 87gas.I wouldn't touch it for now. I would set the maximum to between 32 to 34, and let the idle be what it will be. Personally, I'd like to see that kink up a lil higher, at say 2800. But if the power runs are clean with no detonation, then let it be.
Then I would put the biggest Vcan on there I could find, or mod the one you got, in either case crank it up to about 22*. Then adjust the screw inside it to bring it in as fast as possible .
Now look on your graph, and add 22* to every point on it.
That will be the grand total available at Part Throttle.
Notice that at ~1800 this will be 22+25=47, Perhaps a tad high, we'll see.
Then, look at ~2400; and I see 22+31=53*, Perfect for cruising with 2.94s;
And finally at ~2800, and I see 22+32=54*, Perfect for cruising with 3.55s.
Do not confuse piston slap at low coolant temps, for detonation after fully warmed up. I have never heard detonation at idle. If you have piston slap, you just gotta ask why it's there. Did you build it into there on purpose, or?
IDK which 600Holley you have but Holleys are not known for their stellar fuel-economy. A better choice is something with triple boosters and metering rods. Even if it's a big TQ or Q-jet, or just about any spreadbore..... installed on a spreadbore intake. I wouldn't mess with adapters. I have a smallport, cast-iron, spreadbore intake, so I know they are out there. Your combo might be perfect for an Offy Dual-Port. I recently acquired one of these, but haven't had a chance to experiment with it yet. At your stated useage,with no WOT running, consider a 2bbl carb.
OK I see your 4-corner 600. The problem with that carb is that it isn't really engineered for economy, adjusting the low-speed circuits is not easy. Whereas the TQ and QJs are; they have multiple ways to adjust just about anything as regards the lowspeed circuits. If you don't need or want the secondaries, then you can simply block them closed. If you do that with the TQ, then get the bigger-rated TQ; it has slightly larger primaries.
But honestly, The TQ runs super- great on a smogger-teen. I have one on my winter motor. The 850 no less. The engine will never pull more than it can pull, so if that happens to be 200 or 250 cfm, well that's all the 850 will pass. But the 1.5" primaries (on the big one), have almost instant throttle response, so if you can make a TQ bog on a smogger-teen, then it must be your first tune,lol.
But hey, I also gotta tell you that the Holley 600 can make 32mpgUS on my 367HO..... albeit at 65=1580rpm.heehee
Also at your stated useage, You can run a ton of cylinder pressure. The rules that apply to running WOT with a 4bbl do not apply to you. But you would need a decent closed chamber shape,like Magnum heads..... jus saying.
Then I would put the biggest Vcan on there I could find, or mod the one you got, in either case crank it up to about 22*. Then adjust the screw inside it to bring it in as fast as possible .
Now look on your graph, and add 22* to every point on it.
That will be the grand total available at Part Throttle.
Notice that at ~1800 this will be 22+25=47, Perhaps a tad high, we'll see.
Then, look at ~2400; and I see 22+31=53*, Perfect for cruising with 2.94s;
And finally at ~2800, and I see 22+32=54*, Perfect for cruising with 3.55s.
Do not confuse piston slap at low coolant temps, for detonation after fully warmed up. I have never heard detonation at idle. If you have piston slap, you just gotta ask why it's there. Did you build it into there on purpose, or?
IDK which 600Holley you have but Holleys are not known for their stellar fuel-economy. A better choice is something with triple boosters and metering rods. Even if it's a big TQ or Q-jet, or just about any spreadbore..... installed on a spreadbore intake. I wouldn't mess with adapters. I have a smallport, cast-iron, spreadbore intake, so I know they are out there. Your combo might be perfect for an Offy Dual-Port. I recently acquired one of these, but haven't had a chance to experiment with it yet. At your stated useage,with no WOT running, consider a 2bbl carb.
OK I see your 4-corner 600. The problem with that carb is that it isn't really engineered for economy, adjusting the low-speed circuits is not easy. Whereas the TQ and QJs are; they have multiple ways to adjust just about anything as regards the lowspeed circuits. If you don't need or want the secondaries, then you can simply block them closed. If you do that with the TQ, then get the bigger-rated TQ; it has slightly larger primaries.
But honestly, The TQ runs super- great on a smogger-teen. I have one on my winter motor. The 850 no less. The engine will never pull more than it can pull, so if that happens to be 200 or 250 cfm, well that's all the 850 will pass. But the 1.5" primaries (on the big one), have almost instant throttle response, so if you can make a TQ bog on a smogger-teen, then it must be your first tune,lol.
But hey, I also gotta tell you that the Holley 600 can make 32mpgUS on my 367HO..... albeit at 65=1580rpm.heehee
Also at your stated useage, You can run a ton of cylinder pressure. The rules that apply to running WOT with a 4bbl do not apply to you. But you would need a decent closed chamber shape,like Magnum heads..... jus saying.
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glhx
Well-Known Member
Just to address this first before anything else.
This is pinging at idle. It’s a light ping.
When I put it in gear it gets worse and louder. More consistent.
The car is running 20hg and for some reason it’s idling at 600.
I was checking the springs and weights before this. I pushed them out and forced them to where they were completely out. The last 1/8” was hard and I’m wondering if the distributor puts enough force on them to get them that far. I’m wondering if I stretched the springs and now they are coming in at idle. Doubt it since rpm doesn’t raise up.....in fact it’s too low.
I know at 13° base timing I shouldn’t have this problem. When I was at 15° I didn’t have this problem. So why now...?
What I will do tomorrow is use a piston stop to see if the harmonic Timing mark is off. Can’t hurt to do this anyway as I’m sure the harmonic balancer is original. As old as the chain is....it doesn’t jump around. The engine is completely stock short block. Just a streetmaster, Hei, and a Holley 600 added to it
Any thoughts on the pinging all of a sudden
Learning a lot but not all there?
I’ll be happy just to get it running right. I feel like I’m close
This is pinging at idle. It’s a light ping.
When I put it in gear it gets worse and louder. More consistent.
The car is running 20hg and for some reason it’s idling at 600.
I was checking the springs and weights before this. I pushed them out and forced them to where they were completely out. The last 1/8” was hard and I’m wondering if the distributor puts enough force on them to get them that far. I’m wondering if I stretched the springs and now they are coming in at idle. Doubt it since rpm doesn’t raise up.....in fact it’s too low.
I know at 13° base timing I shouldn’t have this problem. When I was at 15° I didn’t have this problem. So why now...?
What I will do tomorrow is use a piston stop to see if the harmonic Timing mark is off. Can’t hurt to do this anyway as I’m sure the harmonic balancer is original. As old as the chain is....it doesn’t jump around. The engine is completely stock short block. Just a streetmaster, Hei, and a Holley 600 added to it
Any thoughts on the pinging all of a sudden
Learning a lot but not all there?
I’ll be happy just to get it running right. I feel like I’m close
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James Clews
Well-Known Member
I have never heard an engine ping at idle! I think you are confused with something else?
James Clews
Well-Known Member
Well after thinking about it our 351 clevelands in the early eighties used to run on when you turned the ignition off ( dieseling) and they did knock something terrible until they stopped but never seen a motor ping at idle.
glhx
Well-Known Member
Maybe I’m confusing it. There is definitely a sound there. I don’t really have a frame of reference for this except for when it pinged while I was driv8ng with an unlimited vacuum advance. It sounds like a hammer tapping on the exhaust pipe. It was for sure a ping. I’d never heard anything like it before. When I turn it off it just shuts down without any deiseling.
It doesn’t make sense if it is too advanced. I don’t think according to initial timing and idle....that it’s advanced enough.
The plugs have a darker brown color but look decent.
It’s also really choppy from off idle to exactly 2400rpm......then it smooths out. I gauge this by the interior parts shaking.
Also. The original problem that started this thread is mostly gone. Changing the jets back to stock 64 helped a lot with this while the car was warm. Changing over from a pink cam to the orange cam made the throttle instant and fixed that the car wanted to die ,but it stayed choppy and and this is throughout the transition. Like the transition is running lean. I don’t have the tools to adjust the ifr yet.
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AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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Choppiness can be due to many reasons. It could be the cam, or the cam and log-manifold combo. Or it could be AFR and or timing. Or it could be a mechanical deal. Or you could have the firing order wrong or a crossfire, or cracked plug insulator. Following is a test for you but it assumes that
the point-gap is stable, with the proper dwell occurring and not wandering. If the dwell is jumping around due to a worn-out D, or worn out point return spring, or a defective condenser, then the timing is similarly jumping around. So the first thing you gotta do is prove your timing is stable below 2400rpm. Disconnect the Vcan, and check it out. If stable, reconnect the Vcan and check it out. If that also passes, then start at Part I
Looking at your curve, I could see the choppiness being too much advance if the Vcan is hooked to manifold vacuum, or if it is bringing too much too early.
Here is a test for you; it assumes the ignition system is 100% working
Part I
Do not disconnect the Vcan.
Put the idle speed to 2400 and check the timing. This is the smooth out rpm right. Write it down.
Next put the rpm down to 2200, you said now it is choppy right. Put the timing light on it, and start taking out timing, by cranking the D, until it smooths out. If it never smooths out, add some back in until it does, and write it down. If it does not smooth out no matter what you do to the timing, then you have a different issue, so put the timing back, and go down to part II.
But to continue; assuming that you found a timing that was smooth, write it down. Continue this way in 200 rpm drops until the Vcan drops out, maybe around 1600rpm.
Plot it out on a graph. This is your maximum timing at those rpms, under no-load conditions. Now you have to modify your system to meet those needs.
Part II
if the problem was not in the timing, then perhaps it is in the fueling.
So disconnect the Vcan, and crank up the idle speed to perhaps 1600rpm. Then slowly take away air by covering the airhorn with a shoprag. If it smooths out, you have found your problem. But if it slows down a bunch;stop the test. Next, allow the rpm to stabilize, then pinch the fuel supply hose shut... and wait. Soon one of three things is gonna happen;
1) the engine will run choppy for a bit,possibly smooth out, then slow down and stall. If it smooths out, then it's rich. If it doesn't smooth out, then its probably normal, and the problem lies elsewhere.
2) the idle speed will rise, the engine will smooth out. Then the Rs will begin to drop,and as the engine struggles for fuel, things will be as at #1 . This is too rich
3) the engine will immediately lose Rs run worse and then die. This is probably lean.
So now, if #2 or #3, then you will have to prove the low speed circuits are clean, and if the are; then you will have to change the float level and/ or check the fuel pressure.
But if you got a #1, then we need to do some more digging, return the engine to idle. Go to Part III
Part III
Back up the bus. I think you missed something in the preliminary assessment. Go back looking for crossfires or cracked plug insulators, and a wrong firing order...
Run the engine up to 1600rpm until it gets choppy. Then one by one, remove the plug wires, until you find one that makes no difference if it is on or off, or it runs worse with it on. Write it down, and go look for another one. If you have two of them check the firing order, or if they follow eachother in the firing order, then separate the wires a couple of inches and if the problem persists then check the cap.But if the issue goes away with the wires separated, buy some decent wires. But if only one, then either replace the plug or sub in one from another cylinder. If the issue follows the plug then replace it. If the issue stays where you found it, replace the wire.
But if everything checks out OK here; then Part IV
Part IV
Time for a compression test
If the numbers come in even, then off with the valve covers. You will be looking for bent pushrods, and/or valve springs with no tension on them. The valves to be checked have to be on the base circle. That is to say with the piston for that cylinder close to TDC compression. If you can spin any by hand, you gotta fix that first. Sometimes I have done this with the engine idling. If you see any springs rotating or spinning, you got a problem.
But if the numbers are not even, within about 10 to 15 psi, you got a mechanical problem. To see where it lies, next comes a LeakDown test, ti find if it is the rings or the valves.
Part V
loose ends
To prove the low speed is working, with the engine idling, stick a couple of fingers down the primary side and block the Idle Air Bleeds. If the engine runs worse, at least one of them is working so test them individually. Of course the Transfer port exposure has to be close, heehee. If you have too much idle timing the throttles will be too far closed and the mixture screws will be cranked way out. The only cure for this is to back off the idle timing and open up the throttles a tad with the speed screw, then restore the mixture screw settings to the center of their range. Now repeat the IAB test. If you find one that doesn't make a difference, clean it out.
Part VI
Check the cam and cam-timing, maybe you got a wiped lobe or two, or a 292/292/108 in there lol.
Part VI
That's all I got, except to say you can jump to any part at any time if you suspect a particular problem. I for instance, just go straight to the compression test. While I'm taking the plugs out, I can check for cracked insulators, and I can check the wire routing and firing order. So maybe I catch something obvious and stay the compression test. And maybe not.
Part VII
Odds and Ends
Cracked insulators are or can be, very hard to see with the naked eye. Many times the diagnoses is by subbing in a new or different plug.
I remember one time in a 4 cylinder, swapping plugs with no different results. Turns out the plug I took from one hole and moved to the suspect hole, was also cracked. Four new plugs cured the problem. Then I had to figure out why it had two cracked insulators. I could not see the cracks until I put the magnifier on them. My boss was kindof ticked. He couldn't see the cracks either. The customer was kindof ticked too, cuz, he said, he had recently changed them. He couldn't see the cracks either until looking thru the magnifier. AJ was in the doghouse. Even moreso after I presented the bill for a replacement head installed, and a new knocksensor.. Turns out, the head was leaking water into the chambers, and the knocksenser wasn't sensing.
I don't think you have a water problem.
But you saidso yourself it was detonating at idle in N/P with no load on it. The detonation may have killed a plug or two.
the point-gap is stable, with the proper dwell occurring and not wandering. If the dwell is jumping around due to a worn-out D, or worn out point return spring, or a defective condenser, then the timing is similarly jumping around. So the first thing you gotta do is prove your timing is stable below 2400rpm. Disconnect the Vcan, and check it out. If stable, reconnect the Vcan and check it out. If that also passes, then start at Part I
Looking at your curve, I could see the choppiness being too much advance if the Vcan is hooked to manifold vacuum, or if it is bringing too much too early.
Here is a test for you; it assumes the ignition system is 100% working
Part I
Do not disconnect the Vcan.
Put the idle speed to 2400 and check the timing. This is the smooth out rpm right. Write it down.
Next put the rpm down to 2200, you said now it is choppy right. Put the timing light on it, and start taking out timing, by cranking the D, until it smooths out. If it never smooths out, add some back in until it does, and write it down. If it does not smooth out no matter what you do to the timing, then you have a different issue, so put the timing back, and go down to part II.
But to continue; assuming that you found a timing that was smooth, write it down. Continue this way in 200 rpm drops until the Vcan drops out, maybe around 1600rpm.
Plot it out on a graph. This is your maximum timing at those rpms, under no-load conditions. Now you have to modify your system to meet those needs.
Part II
if the problem was not in the timing, then perhaps it is in the fueling.
So disconnect the Vcan, and crank up the idle speed to perhaps 1600rpm. Then slowly take away air by covering the airhorn with a shoprag. If it smooths out, you have found your problem. But if it slows down a bunch;stop the test. Next, allow the rpm to stabilize, then pinch the fuel supply hose shut... and wait. Soon one of three things is gonna happen;
1) the engine will run choppy for a bit,possibly smooth out, then slow down and stall. If it smooths out, then it's rich. If it doesn't smooth out, then its probably normal, and the problem lies elsewhere.
2) the idle speed will rise, the engine will smooth out. Then the Rs will begin to drop,and as the engine struggles for fuel, things will be as at #1 . This is too rich
3) the engine will immediately lose Rs run worse and then die. This is probably lean.
So now, if #2 or #3, then you will have to prove the low speed circuits are clean, and if the are; then you will have to change the float level and/ or check the fuel pressure.
But if you got a #1, then we need to do some more digging, return the engine to idle. Go to Part III
Part III
Back up the bus. I think you missed something in the preliminary assessment. Go back looking for crossfires or cracked plug insulators, and a wrong firing order...
Run the engine up to 1600rpm until it gets choppy. Then one by one, remove the plug wires, until you find one that makes no difference if it is on or off, or it runs worse with it on. Write it down, and go look for another one. If you have two of them check the firing order, or if they follow eachother in the firing order, then separate the wires a couple of inches and if the problem persists then check the cap.But if the issue goes away with the wires separated, buy some decent wires. But if only one, then either replace the plug or sub in one from another cylinder. If the issue follows the plug then replace it. If the issue stays where you found it, replace the wire.
But if everything checks out OK here; then Part IV
Part IV
Time for a compression test
If the numbers come in even, then off with the valve covers. You will be looking for bent pushrods, and/or valve springs with no tension on them. The valves to be checked have to be on the base circle. That is to say with the piston for that cylinder close to TDC compression. If you can spin any by hand, you gotta fix that first. Sometimes I have done this with the engine idling. If you see any springs rotating or spinning, you got a problem.
But if the numbers are not even, within about 10 to 15 psi, you got a mechanical problem. To see where it lies, next comes a LeakDown test, ti find if it is the rings or the valves.
Part V
loose ends
To prove the low speed is working, with the engine idling, stick a couple of fingers down the primary side and block the Idle Air Bleeds. If the engine runs worse, at least one of them is working so test them individually. Of course the Transfer port exposure has to be close, heehee. If you have too much idle timing the throttles will be too far closed and the mixture screws will be cranked way out. The only cure for this is to back off the idle timing and open up the throttles a tad with the speed screw, then restore the mixture screw settings to the center of their range. Now repeat the IAB test. If you find one that doesn't make a difference, clean it out.
Part VI
Check the cam and cam-timing, maybe you got a wiped lobe or two, or a 292/292/108 in there lol.
Part VI
That's all I got, except to say you can jump to any part at any time if you suspect a particular problem. I for instance, just go straight to the compression test. While I'm taking the plugs out, I can check for cracked insulators, and I can check the wire routing and firing order. So maybe I catch something obvious and stay the compression test. And maybe not.
Part VII
Odds and Ends
Cracked insulators are or can be, very hard to see with the naked eye. Many times the diagnoses is by subbing in a new or different plug.
I remember one time in a 4 cylinder, swapping plugs with no different results. Turns out the plug I took from one hole and moved to the suspect hole, was also cracked. Four new plugs cured the problem. Then I had to figure out why it had two cracked insulators. I could not see the cracks until I put the magnifier on them. My boss was kindof ticked. He couldn't see the cracks either. The customer was kindof ticked too, cuz, he said, he had recently changed them. He couldn't see the cracks either until looking thru the magnifier. AJ was in the doghouse. Even moreso after I presented the bill for a replacement head installed, and a new knocksensor.. Turns out, the head was leaking water into the chambers, and the knocksenser wasn't sensing.
I don't think you have a water problem.
But you saidso yourself it was detonating at idle in N/P with no load on it. The detonation may have killed a plug or two.
glhx
Well-Known Member
This doesn’t make sense to me and might be a problem with timing. I can’t really wrap my head around it.
I decided to check the harmonic balancer with a piston stop. I checked it three times.
(Just to see about how far I had to put the piston stop down in the cylinder. It ended up 7/8 was the best depth for close measuring)
The timing mark on the harmonic is spot on for top dead center.
The poroblem is......in the first picture. That’s top dead center. When I start the car. It backfires out the intake horribly and barely stays running.
In the second picture. I move the distributor and the car starts and runs well. The problem is. This is where 0° is on my timing light.
0° should be represented by the first picture but it’s not. It’s represented in the light by he second picture.
I don’t know why. There’s no way I can get this properly timed until I understand the logic behind this.
This is the gm Hei style distributor. I took the points distributor out becuase the rubbing block was worn out and the vacuum advance canister was seized. So far I’ve not hooked up the v can. I’ve not gotten the total timing done yet so I’ve been leaving the v can unhooked.
Had I not checked for 0° I would have never even noticed this
Is this a timing chain problem. A distributor installation problem?did I index the distributor wrong when I put it in?
I’ll have to pick back up on the timing adjustment curve and graphing after sorting this out.
The timing chain is original.
Also.....I think what I was hearing that I thought was ping. Was the car missing. The sounds were similar.....the miss was a slightly different pitch and lower volume sound. I can tell the difference now.
........ I did break a plug in half when I ran it lean a few days ago. When I changed the jets I didn’t hook up the accelerator pump and the plugs ended up white. It left me stranded a mile away from the house. I waited for it to cool back down and ran it back home in the transition slots only. Slow moving up hill but it worked.
.......so there may be other plugs that are damaged. I only replaced that one plug. Trying to get this all sorted out before I start doing maintenance work. I’ll change the oil and replace the plugs. I want to get it sorted and then do all that so I’m not rebreakkng stuff.
I have to advance the timing a lot before it even reads 0° on the timing light when the light is set to 0°.
The pictures depict the view from the front of the engine and are accurate to what I’m seeing. I really have to move it that far away from TDC to get it to read 0° On the light.
I decided to check the harmonic balancer with a piston stop. I checked it three times.
(Just to see about how far I had to put the piston stop down in the cylinder. It ended up 7/8 was the best depth for close measuring)
The timing mark on the harmonic is spot on for top dead center.
The poroblem is......in the first picture. That’s top dead center. When I start the car. It backfires out the intake horribly and barely stays running.
In the second picture. I move the distributor and the car starts and runs well. The problem is. This is where 0° is on my timing light.
0° should be represented by the first picture but it’s not. It’s represented in the light by he second picture.
I don’t know why. There’s no way I can get this properly timed until I understand the logic behind this.
This is the gm Hei style distributor. I took the points distributor out becuase the rubbing block was worn out and the vacuum advance canister was seized. So far I’ve not hooked up the v can. I’ve not gotten the total timing done yet so I’ve been leaving the v can unhooked.
Had I not checked for 0° I would have never even noticed this
Is this a timing chain problem. A distributor installation problem?did I index the distributor wrong when I put it in?
I’ll have to pick back up on the timing adjustment curve and graphing after sorting this out.
The timing chain is original.
Also.....I think what I was hearing that I thought was ping. Was the car missing. The sounds were similar.....the miss was a slightly different pitch and lower volume sound. I can tell the difference now.
........ I did break a plug in half when I ran it lean a few days ago. When I changed the jets I didn’t hook up the accelerator pump and the plugs ended up white. It left me stranded a mile away from the house. I waited for it to cool back down and ran it back home in the transition slots only. Slow moving up hill but it worked.
.......so there may be other plugs that are damaged. I only replaced that one plug. Trying to get this all sorted out before I start doing maintenance work. I’ll change the oil and replace the plugs. I want to get it sorted and then do all that so I’m not rebreakkng stuff.
I have to advance the timing a lot before it even reads 0° on the timing light when the light is set to 0°.
The pictures depict the view from the front of the engine and are accurate to what I’m seeing. I really have to move it that far away from TDC to get it to read 0° On the light.
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glhx
Well-Known Member
Been thinking about this a lot.
I might have my distributor indexed off 1 tooth. I remember trying to put the gear in and how difficult it was. I’ve never had to install a gear before in a Chrysler. The gear only wanted to slide into the oil pump in 2 places. This could be because the oil pump wasn’t moving with the gear and when I put it in.....it was just hitting the oil pump key wrong. One of those places was completely wrong. Is there a way to turn the oil pump to make indexing it a little easier?
What I’m thinking is that by indexing the gear wrong....if that’s what I’ve done. I’ve retarded the timing and it might be sitting at like 10° Or more after TDC.
I’m using the distributor advance to bring it back to 0° .......and then advancing it to where I need it.so if my timing light could possibly read regraded. I could see where that is. So in a sense.....maybe I’m advancing it 30° From TDC to get to 15° Initial Advanced
If this is the case.....then it’s fine and I can get back to all this other stuff. Either way I’m a lot further than when I started and have leaRned a lot from you guys.... I went back through this thread and noticed that I didn’t know enough to understand some of the advice given. You almost have to think like an engine.
Originally I thought the main jets were 62......they were not. They were 602 or basically #60 this helped with the lean spot when I went to #64....it must have been when main cruise was activated. When I put #64 in there it made a huge difference. The car still had the lean spot in acceleration off idle. The orange cam fixed that. I’ve heard that bigger jets can affect idle due to head pressure. Almost like raising the float up to make the gas in the float bowl put pressure on the main jets. If this is true or not I don’t know. The bigger jets did take the lean stumble out and left a lean hesitation. ......having a tach now finalLy installed tells me a lot more about exact rpm problems. This year I’ll get into using a wide band but I can’t do that yet.
I still need to sort out that lean transition.....it’s when I go into it slow or fast it has hesitation.....it’s not bad....it’s just not smooth....if I get the timing right, then I put in the metering block I have drilled at The ifr and adjust it.
I don’t have the brass inserts yet and the inserts in the metering block are .033 which would make the ifr and transition way too rich. I’m thinking I need to be at .031. Supposedly, Holley made some carbs that have this lean spot.
There are other things to check first.....like all the timing. One other thing.....this carburetors metering block is not the one that came wothnhe carb.....at least I don’t think. My carb is 2009. When I checked the metering block. It had the ifr down in the lower spots. I think Holley had moved them to the upper spots by this time. .....for all I know. That metering block could be from a 500. I think whoever had this carb before me, just threw it together from whatever they had lying around. ...why would someone put #60 jets in a Holley and then open up the secondaries 1/4”. Then install a a fast idle cam kit .......and then take out the screw to disable it.....
I won’t hook up he v can until I get the total right. One step at a time.
Also......someone told me that Chrysler distributors were not supposed to be set up at TDC. I’ve never heard this before and it doesn’t make any sense.
I might have my distributor indexed off 1 tooth. I remember trying to put the gear in and how difficult it was. I’ve never had to install a gear before in a Chrysler. The gear only wanted to slide into the oil pump in 2 places. This could be because the oil pump wasn’t moving with the gear and when I put it in.....it was just hitting the oil pump key wrong. One of those places was completely wrong. Is there a way to turn the oil pump to make indexing it a little easier?
What I’m thinking is that by indexing the gear wrong....if that’s what I’ve done. I’ve retarded the timing and it might be sitting at like 10° Or more after TDC.
I’m using the distributor advance to bring it back to 0° .......and then advancing it to where I need it.so if my timing light could possibly read regraded. I could see where that is. So in a sense.....maybe I’m advancing it 30° From TDC to get to 15° Initial Advanced
If this is the case.....then it’s fine and I can get back to all this other stuff. Either way I’m a lot further than when I started and have leaRned a lot from you guys.... I went back through this thread and noticed that I didn’t know enough to understand some of the advice given. You almost have to think like an engine.
Originally I thought the main jets were 62......they were not. They were 602 or basically #60 this helped with the lean spot when I went to #64....it must have been when main cruise was activated. When I put #64 in there it made a huge difference. The car still had the lean spot in acceleration off idle. The orange cam fixed that. I’ve heard that bigger jets can affect idle due to head pressure. Almost like raising the float up to make the gas in the float bowl put pressure on the main jets. If this is true or not I don’t know. The bigger jets did take the lean stumble out and left a lean hesitation. ......having a tach now finalLy installed tells me a lot more about exact rpm problems. This year I’ll get into using a wide band but I can’t do that yet.
I still need to sort out that lean transition.....it’s when I go into it slow or fast it has hesitation.....it’s not bad....it’s just not smooth....if I get the timing right, then I put in the metering block I have drilled at The ifr and adjust it.
I don’t have the brass inserts yet and the inserts in the metering block are .033 which would make the ifr and transition way too rich. I’m thinking I need to be at .031. Supposedly, Holley made some carbs that have this lean spot.
There are other things to check first.....like all the timing. One other thing.....this carburetors metering block is not the one that came wothnhe carb.....at least I don’t think. My carb is 2009. When I checked the metering block. It had the ifr down in the lower spots. I think Holley had moved them to the upper spots by this time. .....for all I know. That metering block could be from a 500. I think whoever had this carb before me, just threw it together from whatever they had lying around. ...why would someone put #60 jets in a Holley and then open up the secondaries 1/4”. Then install a a fast idle cam kit .......and then take out the screw to disable it.....
I won’t hook up he v can until I get the total right. One step at a time.
Also......someone told me that Chrysler distributors were not supposed to be set up at TDC. I’ve never heard this before and it doesn’t make any sense.
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nm9stheham
Well-Known Member
I think what your diagrams show is informative.... As background on the rotor position: At low RPM's with no mechanical advance, the rotor should be slightly CCW from directly pointing at the #1 spark tower on the cap when #1 fires.. As the ignition timing mechanically advances, the rotor position will advance CW relative to the #1 spark tower when #1 fires. The initial CCW offset at low RPM's is needed so that when the rotor moves CW with full mechanical advance, the full mech advance position is not TOO far CW to jump to the proper spark tower. This is called 'rotor phasing'; it is not just a Mopar thing.
Your left hand diagram, for the true TDC, shows the rotor to be pretty close to where it should be. So the rotor phasing looks acceptable.
Where you show the rotor halfway between #1 and #8 spark tower, for the supposed '0*' on the timing light' is a big problem. In that rotor position, the spark can jump to #1 or #8 tower when it fires for #1. If it jumps to #8 then, #8 is being fired somewhere around 90* advance.... this will happen each time the ignition fires... it can go to the right cylinder OR the next one in the firing order. No wonder you get pinging, misfires, and backfires!
The real problem IMHO: The physical point of rotation at which the ignition correctly fires at around 0* timing puts the rotor position waaay off and the spark can jump to the wrong tower and cause all sorts of havoc. This could be due to:
Hope this helps.
Your left hand diagram, for the true TDC, shows the rotor to be pretty close to where it should be. So the rotor phasing looks acceptable.
Where you show the rotor halfway between #1 and #8 spark tower, for the supposed '0*' on the timing light' is a big problem. In that rotor position, the spark can jump to #1 or #8 tower when it fires for #1. If it jumps to #8 then, #8 is being fired somewhere around 90* advance.... this will happen each time the ignition fires... it can go to the right cylinder OR the next one in the firing order. No wonder you get pinging, misfires, and backfires!
The real problem IMHO: The physical point of rotation at which the ignition correctly fires at around 0* timing puts the rotor position waaay off and the spark can jump to the wrong tower and cause all sorts of havoc. This could be due to:
- the vacuum advance plate being wrong or installed wrong (puts the pickup in the wrong place relative to the reluctor teeth)
- the reluctor being in the wrong position relative to the rotor (not sure how that happens)
- distributor cap wrong or being grossly misalinged
- pickup wires being reversed for certain types of pickups which would make things fire 30-40-50* early or late
Hope this helps.
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glhx
Well-Known Member
I see what your saying........
Man.....that’s kind of a big problem.
How can I fix this this issue or modify it?
I see that if I move the rotor back a tooth....I feel like it would advance the timing back to zero.....but I’m really not.
the distributor would just follow the problem.....I think.....I would just be turning the distributor and having to advance it again except it would just be further to the right. I don’t think it would solve it.
I’ll post a picture of it on the car instead of a diagram.....maybe even a video.
There is something odd about it that what you say might make sense.
When I shut the car off and immediately restart it. Sometimes it backfires and sometimes it doesn’t. If I wait for 3 seconds....it doesn’t backfire.
You kind of get a feel for how to start it. This is at 16°
It might mean it’s hitting the wrong tower wherever it is.
I’ve never had this problem but I’ve also never had a car sitting at 16°And I’ve never had a car that didn’t line up TDC at 0° and start just fine. I used to start there and go to 7°. The engine really likes 16° and the start is very crisp. It feels like it should and like I always wanted it to. Kind of aggressive start. It doesn’t kick back hot.....and why would it.
Now.....when I set it to 20°.....it backfired worse and more consistently.
The engine didn’t like 20......and if you say it right....it makes sense because it’s putting it even close to the next tower.
So basically this is advanced so far that it’s hitting the number 8 tower sometimes
Sigh......
I don’t even know how to begin to fix something like this. ....
Any ideas?
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nm9stheham
Well-Known Member
Well the most likely causes are the 4 possible causes I listed. Some may add to that list. I don't think it is a big problem.... just maybe new.
Moving the distributor rotor back a tooth will not fix this particular problem.
Checking these are pretty self-explanatory. You may need to find some pix to compare your distributor for where the reluctor should point. Or post a pix of the top of the shaft with the rotor removed and the reluctor points and pickup visible so others can compare to theirs.
I am assuming what you have for pickup so bear with me:
Look at the pickup coil riding on the plate that the vacuum advance can move. There should be a thin gap visible on the surface that faces the reluctor teeth and perhaps a mark on top to match that gap's location.
Look to see if, when the rotor is very close to pointing at spark tower, that one of the pointy teeth on the reluctor is pointing exactly at that gap on the pickup.
Based on what seems to be going on:
Moving the distributor rotor back a tooth will not fix this particular problem.
Checking these are pretty self-explanatory. You may need to find some pix to compare your distributor for where the reluctor should point. Or post a pix of the top of the shaft with the rotor removed and the reluctor points and pickup visible so others can compare to theirs.
I am assuming what you have for pickup so bear with me:
Look at the pickup coil riding on the plate that the vacuum advance can move. There should be a thin gap visible on the surface that faces the reluctor teeth and perhaps a mark on top to match that gap's location.
Look to see if, when the rotor is very close to pointing at spark tower, that one of the pointy teeth on the reluctor is pointing exactly at that gap on the pickup.
Based on what seems to be going on:
- If it is lined up that way, then the likely problem is the pickup leads to the ignition module are reversed. That is the last of the 4 problems listed.
- If it is not, then any of the 1st 3 problems are possible causes.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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Agreed, OP;you can chase that D all around the circle and every position you try, you will crank the D back to the vane and end up exactly where you started, just with the rotor in a new place. So then you rewire the cap and nothing has change except the time of day.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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Ignore that timing lite for a couple of minutes. Just start the car , and advance the timing until it runs decent. Reduce the Curb-idle speed back to 800. Defeat the Vcan. Blip the throttle a few times; Still got backfires? Check that your Accelerator pump is spraying. If yes, and this is a metering rod carb, make sure the rods are staying down with light blips and popping up with hard ones.
Read the timing.
If it's over 20*, reset your Transfer-slot sync. With a smaller than 228@.050 cam, close the secondaries up tight but not sticking. Set the mixture screws in the center of their range. Clamp off the brake booster hose, if you have one. Now start her up again. DO NOT touch the curb-idle screw. Instead, STILL ignoring the timing lite, retard the timing to obtain 750rpm. Again blip the throttle. Still got backfires? Leave the timing alone for now, timing is not the problem.
Instead, now rev it up slowly to 3500rpm listening for ignition crap out and backfiring. What you are doing is causing the flyweights to fully advance the rotor, and if the phasing is off, sooner or later, the spark is gonna start jumping to the wrong towers. By 3500 the timing is usually fully advanced, so if it ain't barking, it's fine. Hook the Vcan back up and repeat.
No barking now..... I would be checking split-overlap.
Barking now,
Engine off;I would set the crank to 15*advanced for #1TDC-compression; you will need an indexed balancer or a timing tape, or you can farmer measure it using 1.5 times 10 on the timing tab, accuracy ain't important right now.
Ok so when that is done, pop the cap and make sure the rotor is in the general vicinity of the tower that feeds the wire to #1 cylinder. Then; if it is put it back on.
Next scribe a line on the D on the side of the Distributor body directly in line with the center of the #1 tower. Then scribe shorter lines to the next closer tower in each direction. Again accuracy is not critical; I use a Sharpie.
Next pop the cap off again and set it aside. Observe where the rotor is. It should be closer to that long center scribe-line than to any other.
Grab the rotor and twist it as far as it goes; It should pass the long scribe-line, but stay nearer to it than the next short scribe line. If it gets near to or over the half way point, the spark is gonna take the path of least resistance.
Whenever you blip the throttle, you are increasing the EFFECTIVE compression ratio in every cylinder in it's time. But the chambers adjacent to the one under compression offer less resistance to the spark, so it attacks them. The one behind it in the firing order is on exhaust, so the engine will never notice a fire in that hole,and the rotor is not traveling in that direction, so you can ignore that. But the next one coming up is beginning it's compression stroke, so if the spark jumps to it, it is possible the intake valve is not yet fully closed. Of course if that AF charge gets ignited at this time, the now on-fire gasses are gonna escape up into the intake manifold, and try to lite-off everything in there too. At idle, there is not usually enough oxygen in there to support much so all you get is a lil fizzle. But when you blip the throttle, atmosphere slams down the carb throats, and kaboom up comes the fire. Don't be looking down there and blipping! unless you don't mind looking weird with no eyebrows and smelling singed nose hairs for the next two weeks.
Of course this reverse fire can also happen with an intake valve that is not sealing for some other reason as well. Reasons like weak springs; or bent,burned,sticking,or carboned up valves;or loose-clearance guides. Some of these can be caught by a compression test. But if all cylinders are low, you might not suspect anything except worn out.
And of course, if the cam-timing is out, that would do it too. And that would speak to your odd timing results, and miss-phased rotor as well..
Read the timing.
If it's over 20*, reset your Transfer-slot sync. With a smaller than 228@.050 cam, close the secondaries up tight but not sticking. Set the mixture screws in the center of their range. Clamp off the brake booster hose, if you have one. Now start her up again. DO NOT touch the curb-idle screw. Instead, STILL ignoring the timing lite, retard the timing to obtain 750rpm. Again blip the throttle. Still got backfires? Leave the timing alone for now, timing is not the problem.
Instead, now rev it up slowly to 3500rpm listening for ignition crap out and backfiring. What you are doing is causing the flyweights to fully advance the rotor, and if the phasing is off, sooner or later, the spark is gonna start jumping to the wrong towers. By 3500 the timing is usually fully advanced, so if it ain't barking, it's fine. Hook the Vcan back up and repeat.
No barking now..... I would be checking split-overlap.
Barking now,
Engine off;I would set the crank to 15*advanced for #1TDC-compression; you will need an indexed balancer or a timing tape, or you can farmer measure it using 1.5 times 10 on the timing tab, accuracy ain't important right now.
Ok so when that is done, pop the cap and make sure the rotor is in the general vicinity of the tower that feeds the wire to #1 cylinder. Then; if it is put it back on.
Next scribe a line on the D on the side of the Distributor body directly in line with the center of the #1 tower. Then scribe shorter lines to the next closer tower in each direction. Again accuracy is not critical; I use a Sharpie.
Next pop the cap off again and set it aside. Observe where the rotor is. It should be closer to that long center scribe-line than to any other.
Grab the rotor and twist it as far as it goes; It should pass the long scribe-line, but stay nearer to it than the next short scribe line. If it gets near to or over the half way point, the spark is gonna take the path of least resistance.
Whenever you blip the throttle, you are increasing the EFFECTIVE compression ratio in every cylinder in it's time. But the chambers adjacent to the one under compression offer less resistance to the spark, so it attacks them. The one behind it in the firing order is on exhaust, so the engine will never notice a fire in that hole,and the rotor is not traveling in that direction, so you can ignore that. But the next one coming up is beginning it's compression stroke, so if the spark jumps to it, it is possible the intake valve is not yet fully closed. Of course if that AF charge gets ignited at this time, the now on-fire gasses are gonna escape up into the intake manifold, and try to lite-off everything in there too. At idle, there is not usually enough oxygen in there to support much so all you get is a lil fizzle. But when you blip the throttle, atmosphere slams down the carb throats, and kaboom up comes the fire. Don't be looking down there and blipping! unless you don't mind looking weird with no eyebrows and smelling singed nose hairs for the next two weeks.
Of course this reverse fire can also happen with an intake valve that is not sealing for some other reason as well. Reasons like weak springs; or bent,burned,sticking,or carboned up valves;or loose-clearance guides. Some of these can be caught by a compression test. But if all cylinders are low, you might not suspect anything except worn out.
And of course, if the cam-timing is out, that would do it too. And that would speak to your odd timing results, and miss-phased rotor as well..
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