Thanks guys, finding time to solve issues has been a challenge.
I hope to be able to fine tune both timing and carb now.
I hope to be able to fine tune both timing and carb now.
vacuum gauge to solve idle issue
- Thread starter 4spdragtop
- Start date
-
TrailBeast
AKA Mopars4us on Youtube
That WD40 and air trick works, and I'm glad someone who needed it listened and did it.
The only reason it doesn't work is if that's not the problem, but it sure is a quick way to find out.
Yep, when I told Lori last night I was going out to work on it, she looked at clock and rolled her eyes lol
Had the back neighbor pissed as he went and grabbed his big spotlight and shone it my way. Shoulda shown him the Harvest Moon.
When I dialed in the mixture screws snug I waited about 2 minutes and it wouldnt stall lol. I guess quite a bit of junk in there.
About a 15 minute job total with setting initial timing. Then out for 20 minute rip with no issues.
Of course I had to do a drive by of pissed off neighbors lol
Thanks again Greg
Had the back neighbor pissed as he went and grabbed his big spotlight and shone it my way. Shoulda shown him the Harvest Moon.
When I dialed in the mixture screws snug I waited about 2 minutes and it wouldnt stall lol. I guess quite a bit of junk in there.
About a 15 minute job total with setting initial timing. Then out for 20 minute rip with no issues.
Of course I had to do a drive by of pissed off neighbors lol
Thanks again Greg
TrailBeast
AKA Mopars4us on Youtube
Quiet time is 10pm around here and most of the people around me are partyers and make a lot of noise later than that anyway, so I don't feel the least bit sorry for them when I start mine really early in the morning and no one has ever said anything about it other than praise.
As of this morning I have one of their POS GM cars in my back yard since he's paying me to fix some minor issues with it.
Just dumb things like no wipers, no heat, no dash lights or gauges work, runs intermittently on 7 cylinders, drivers windows fits the opening to where you could throw a cat through it and has a nasty exhaust leak under the middle of it somewhere.
You know, just a few minor things.
You are welcome on the hints and tips any time Steve, and I'm sure all of us feel the same.
Lol I hear ya on GM stuff...never again for me. Kia and Hyundai as DD. You cant argue with over 500, 000 kms.
You would think the cat would know better than to go for a ride in a GM. Its gotta know either the car or it are going to be put down lol
You would think the cat would know better than to go for a ride in a GM. Its gotta know either the car or it are going to be put down lol
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
- Joined
- Jan 19, 2014
- Messages
- 24,898
- Reaction score
- 12,251
If the engine continues to run with the idle-speed circuit totally shut off, then the engine must be pulling fuel through the transfers. This speaks to the T-port still being way off. And that is confirmed by the high idle speed.It would seem that there is still more room for improvement.
What is the T-port AJ?
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
- Joined
- Jan 19, 2014
- Messages
- 24,898
- Reaction score
- 12,251
At the bottom is my sig; click on the blue stuff.
AJ's guide to Transfer Port Synchronization
or go to the Holley site.
The gist of it is this: if you have a big-cammed engine,over about 220*, but especially as it gets over 230*, then these engines like a lot of air at idle. The typical solution is to crank up the idle speed with the curb idle screw. But this puts the butterflies too far up the transfer ports, and the idle-ports stop flowing or at the least, slow down drastically. So now you end up with a very high idle and non-functioning idle mixture screws. So then a guy might be tempted to crank in a bunch of timing. Which allows the butterflies to be closed up and restore some or most of the T-port sync. Then you get to deal with the pinging or detonation of possibly over-advanced part-throttle timing, and of course the power-timing is waaay out too.
Setting the T-port sync first, and setting the initial timing a little more conservatively, and giving the engine some bypass air instead, can solve most of these issues.This is called syncing up the Transfer ports.
Keep in mind that cams in the 220 to 230 range, and higher, can easily take 45* of part-throttle timing at 2000 rpm and cruising. And be very happy there. What that indicates is that using the vacuum gauge to set initial timing can easily get you into the 20 to 25 degree zone,possibly more. And the engine will happily idle there;and possibly even cruise with whatever other timings come in.The problems come in the transitions. And yes, at 20 to 25 degrees, the engine will seem to be very snappy from around 1500 to 2500rpm. But with the T-port sync out so far, transitioning from idle to part throttle and back, can sometimes be problematic. And of course, the power timing will be set on self-destruct until you limit it to something more sane like 34* at 3400.
BTW; I titled the guide "AJ's", but I'm sure there were hundreds of guys that figured this stuff out long before me.I just used AJ's cuz I thought it would be easy to find using the search button.And the symptoms were being posted almost non-stop, at the time I typed it out.
As a comparison; My 367 cuber run's a 230*cam and 10.75 Scr with aluminum heads. It runs just fine with 14* of initial. The idle is set at 750 or a little less. The engine will pull the 68 Barracuda(3650#),on flat level ground, down to 500rpm with a 10.97 starter gear(stick-car).The mechanical-advance begins at 1000 and by 2800 the engine is seeing 28*. But it has a slower curve from there to 3400 where the engine sees 34*. I have a 22* vacuum can which starts pulling in timing at about 12 inches and is all done by about 16inches or so. Doing the math for part throttle, it is entirely possible for the engine to be seeing up to 50* of total timing at 2800 rpm.(28 plus 22).
The point is this; very many people say that you need 18* to 25* at idle, and all in by 2500. While this may work for a race car, IMHO;this is not the hot set-up for a street engine with a cam in the 210* to 240* range.
Oh yeah, my engine has almost never run anything but 87E10. And the reason is this; I heard many years ago, that the stuff they put in "premium" gas makes it burn slower. Well to my young mind, I thought: Hmmmmm is slower a good thing? Well it is if it keeps your engine from hammering it's bearings to death.
Peace!
AJ's guide to Transfer Port Synchronization
or go to the Holley site.
The gist of it is this: if you have a big-cammed engine,over about 220*, but especially as it gets over 230*, then these engines like a lot of air at idle. The typical solution is to crank up the idle speed with the curb idle screw. But this puts the butterflies too far up the transfer ports, and the idle-ports stop flowing or at the least, slow down drastically. So now you end up with a very high idle and non-functioning idle mixture screws. So then a guy might be tempted to crank in a bunch of timing. Which allows the butterflies to be closed up and restore some or most of the T-port sync. Then you get to deal with the pinging or detonation of possibly over-advanced part-throttle timing, and of course the power-timing is waaay out too.
Setting the T-port sync first, and setting the initial timing a little more conservatively, and giving the engine some bypass air instead, can solve most of these issues.This is called syncing up the Transfer ports.
Keep in mind that cams in the 220 to 230 range, and higher, can easily take 45* of part-throttle timing at 2000 rpm and cruising. And be very happy there. What that indicates is that using the vacuum gauge to set initial timing can easily get you into the 20 to 25 degree zone,possibly more. And the engine will happily idle there;and possibly even cruise with whatever other timings come in.The problems come in the transitions. And yes, at 20 to 25 degrees, the engine will seem to be very snappy from around 1500 to 2500rpm. But with the T-port sync out so far, transitioning from idle to part throttle and back, can sometimes be problematic. And of course, the power timing will be set on self-destruct until you limit it to something more sane like 34* at 3400.
BTW; I titled the guide "AJ's", but I'm sure there were hundreds of guys that figured this stuff out long before me.I just used AJ's cuz I thought it would be easy to find using the search button.And the symptoms were being posted almost non-stop, at the time I typed it out.
As a comparison; My 367 cuber run's a 230*cam and 10.75 Scr with aluminum heads. It runs just fine with 14* of initial. The idle is set at 750 or a little less. The engine will pull the 68 Barracuda(3650#),on flat level ground, down to 500rpm with a 10.97 starter gear(stick-car).The mechanical-advance begins at 1000 and by 2800 the engine is seeing 28*. But it has a slower curve from there to 3400 where the engine sees 34*. I have a 22* vacuum can which starts pulling in timing at about 12 inches and is all done by about 16inches or so. Doing the math for part throttle, it is entirely possible for the engine to be seeing up to 50* of total timing at 2800 rpm.(28 plus 22).
The point is this; very many people say that you need 18* to 25* at idle, and all in by 2500. While this may work for a race car, IMHO;this is not the hot set-up for a street engine with a cam in the 210* to 240* range.
Oh yeah, my engine has almost never run anything but 87E10. And the reason is this; I heard many years ago, that the stuff they put in "premium" gas makes it burn slower. Well to my young mind, I thought: Hmmmmm is slower a good thing? Well it is if it keeps your engine from hammering it's bearings to death.
Peace!
Last edited:
Thanks AJ will give it a read thru. I agree lots of room for improvement. ...both me and the carb
Ok so idle issue is back with a vengeance lol. Surges huge at idle or under very low throttle.
Sorry bout lousy video quality. Look at the washer fluid sloshing from the surging lol.
Again I checked for vac leak and couldnt detect any.
Blew out idle air circuits, then snugged the screws in, then out 1 1/2 turns.
Initial timing I set about a week ago 16* BTC
New fuel filter about 200 miles ago.
No visible leaks that I can see.
Ive never had the carb apart(other than checking metering rods), Im thinking it might be time to pull the top off and see whats up??
Heres the videos, sorry bout shitty quality
Sorry bout lousy video quality. Look at the washer fluid sloshing from the surging lol.
Again I checked for vac leak and couldnt detect any.
Blew out idle air circuits, then snugged the screws in, then out 1 1/2 turns.
Initial timing I set about a week ago 16* BTC
New fuel filter about 200 miles ago.
No visible leaks that I can see.
Ive never had the carb apart(other than checking metering rods), Im thinking it might be time to pull the top off and see whats up??
Heres the videos, sorry bout shitty quality
65Val
Average Length Member
Is there a buddy that'll lend you known good carb for a trial?
No such luck Dar, Ill pull the top open tomorrow. Carb was new 4 years ago, but time for a look see.I bought these rods n jets earlier in the spring, a switch may be required?
Wish this happened in the spring. Winters coming, going down to -2 tonight.
Wish this happened in the spring. Winters coming, going down to -2 tonight.
65Val
Average Length Member
Now see....you should have taken that job offer out here...then I could lend you a few carbs to try!!! ;-)
Seriously, I doubt a rod or jet change is going to fix your problem. While the carbs apart, blow every passage out with air, and check your float levels.
The surging seemed to stop after you did the first rev-up. Could it be that
the choke butterfly was just closed too far?
Last edited:
Not for what they want for property out there lol.
I should have some time friday to take a look at it. I thought choke too, but it had a credit card thick gap. I read thats proper gap?
Thanks.
I should have some time friday to take a look at it. I thought choke too, but it had a credit card thick gap. I read thats proper gap?
Thanks.
65Val
Average Length Member
Steve....Every engine's different....they all want what they want: timing, carb, mixture, etc.. A creit card gap is a bit too closed. Try backing off the choke butterfly setting a bit on your next cold start and see if that helps.
Well Im into it now. Definitely crap in there. Carb is pretty much stripped down. Factory primary jets are 0.100" metering rods are 7047 (1405 carb) but we added edelbrock electric choke kit 4 years ago.
Besides the cleaning it needed, I think its running rich and might be over carbed for the engine.
So while apart I was going to change metering rods and/or primary jeys or both. Heres kits I have. BUT I don't have any kits for the secondary jets
If I change primaries is it recommended to change secondary as well. Or is its done "as required" ?
Step up springs are factory orange. I have complete spring kit as well
Thanks for the help.
Steve
Besides the cleaning it needed, I think its running rich and might be over carbed for the engine.
So while apart I was going to change metering rods and/or primary jeys or both. Heres kits I have. BUT I don't have any kits for the secondary jets
If I change primaries is it recommended to change secondary as well. Or is its done "as required" ?
Step up springs are factory orange. I have complete spring kit as well
Thanks for the help.
Steve
TrailBeast
AKA Mopars4us on Youtube
Secondaries are usually a secondary concern.
I also agree on the choke setting being too far closed, and it's easy to see what the engine wants for choke just by starting the engine with the air cleaner of and pushing the choke open with your finger while it idling.
It'll smooth out where it likes the choke.
I doubt that carb is too big being a 600cfm, but I will tell you that I ran #.100 jets in my 1406 in the primaries and it was too rich for the 318 no matter what needles or springs I used. (I live at 5,500 feet elevation and that makes a difference)
If I remember I changed to #86 primaries? and it straightened up.
I'm running #90 in the 5.9 Magnum, but don't remember the needles in it, so that makes that statement pointless.
I also agree on the choke setting being too far closed, and it's easy to see what the engine wants for choke just by starting the engine with the air cleaner of and pushing the choke open with your finger while it idling.
It'll smooth out where it likes the choke.
I doubt that carb is too big being a 600cfm, but I will tell you that I ran #.100 jets in my 1406 in the primaries and it was too rich for the 318 no matter what needles or springs I used. (I live at 5,500 feet elevation and that makes a difference)
If I remember I changed to #86 primaries? and it straightened up.
I'm running #90 in the 5.9 Magnum, but don't remember the needles in it, so that makes that statement pointless.
65Val
Average Length Member
Steve...in your 2nd pic, not enough crap to cause your problem. I would just install the metering parts that came stock with the carb...600 is not really over carbed for your engine. Try the choke setting info I posted.
When I check online for cfm formula, online they say max rpm (6000) x cid (273) ÷ 3456 = carb size. Which works out to approx 500 cfm?
If I do swap primary Greg, is #86 the part # ??
I will finish cleaning, reassemble tp stock specs, make adjustments (choke too) and post back.
Thanks guys! Much appreciated.
If I do swap primary Greg, is #86 the part # ??
I will finish cleaning, reassemble tp stock specs, make adjustments (choke too) and post back.
Thanks guys! Much appreciated.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
- Joined
- Jan 19, 2014
- Messages
- 24,898
- Reaction score
- 12,251
Ok, First off was the vacuum advance hooked up during the surging?And where to? And secondly I think the power pistons were popping up.And third;as mentioned the choke needs to be off, and the engine fully warmed up, for any meaningful diagnoses.Unless this behavior only manifests during the warm-up period while the choke-blade is engaged.
And fourthly; carb size.You are idling on the primaries so it is almost, I say"almost" irrelevant as to 500 or 600cfm. If you like, I'll put an 850TQ on and it will not be too big at idle .These style of carbs can be adjusted to work well outside the formula, especially as compression and cams go up..
Ok so now, here's my thinking;
For an engine that is just warming up;if the vacuum advance was hooked up to full-time manifold vacuum: With the choke having set the fast idle cam;engine vacuum brings on the vacuum-advance. But the too-far OPEN choke blade causes the cold engine to run out of fuel,so it slows down, and manifold vacuum drops.This triggers the Metering rods to rise, which dumps fuel in,while simultaneously dropping out the vacuum advance. The extra fuel causes the rpm to rise and the vacuum to build, and that pulls in the Vacuum advance. And so, on it goes.
With the Vcan hooked to the Spark-port,at least the timing would be stable, unless you have a really fast curve in the dizzy.But the rest of the scenario still holds.
But this scenario only works during the warm up period while the choke blade is set, and the engine is relatively cold. As soon as the engine warms up and more importantly, as the choke blade retracts, this behavior would stop.
So to help in diagnoses, try this;
-Make sure the vacuum advance is NOT working at fast idle, by unhooking the can and plugging the line.
-Also make sure the PCV has a stable operation.
-To prove it is a power piston problem, you just need to de-activate them; at idle they should not be working, hot, cold or anywhere in between. You can do that by popping the springs out from under them, and dropping the assemblies back into the jets. This circuit is not used for idling.
-Put a clamp on the vacuum line to the power booster, if you have one.
-If the problem persists, fire your mechanic(me,in this post).....He don't know sh.....lol
And fourthly; carb size.You are idling on the primaries so it is almost, I say"almost" irrelevant as to 500 or 600cfm. If you like, I'll put an 850TQ on and it will not be too big at idle .These style of carbs can be adjusted to work well outside the formula, especially as compression and cams go up..
Ok so now, here's my thinking;
For an engine that is just warming up;if the vacuum advance was hooked up to full-time manifold vacuum: With the choke having set the fast idle cam;engine vacuum brings on the vacuum-advance. But the too-far OPEN choke blade causes the cold engine to run out of fuel,so it slows down, and manifold vacuum drops.This triggers the Metering rods to rise, which dumps fuel in,while simultaneously dropping out the vacuum advance. The extra fuel causes the rpm to rise and the vacuum to build, and that pulls in the Vacuum advance. And so, on it goes.
With the Vcan hooked to the Spark-port,at least the timing would be stable, unless you have a really fast curve in the dizzy.But the rest of the scenario still holds.
But this scenario only works during the warm up period while the choke blade is set, and the engine is relatively cold. As soon as the engine warms up and more importantly, as the choke blade retracts, this behavior would stop.
So to help in diagnoses, try this;
-Make sure the vacuum advance is NOT working at fast idle, by unhooking the can and plugging the line.
-Also make sure the PCV has a stable operation.
-To prove it is a power piston problem, you just need to de-activate them; at idle they should not be working, hot, cold or anywhere in between. You can do that by popping the springs out from under them, and dropping the assemblies back into the jets. This circuit is not used for idling.
-Put a clamp on the vacuum line to the power booster, if you have one.
-If the problem persists, fire your mechanic(me,in this post).....He don't know sh.....lol
Last edited:
With the butterfly valves on the top of the secondaries on the Carter/Edelbrock carbs, you cannot over carb - they will draw only what they need, no more - they act like vacuum secondaries...
Have you looked closely at the transfer slots??? If it happens with the choke on, then smooths out when it kicks down, you may be into the transfer slots... Check them and spray and blow them out with cleaner and compressed air...
Also make sure that the air bleeds are not blocked...
When you sprayed the WD-40 on the idle screws and the idle smoothed out, reminds me of the days when they changed the head gasket on the 2.0 L engine from composite to MLS....
The composite gasket was more tolerant of tool marks on the head face of the block and head. When they changed to the multi layered steel gasket, if the tool marks would get too rough, they would fill the long block air test loop with rejects and back up the line. So they would soak the head gaskets with oil to fill the gaps on the mating face(s) and they would pass the air test and get the line running again. Meanwhile they could go the block or head line to adjust the head face mill cutter for a better finish and get the improved parts into the system...
Have you looked closely at the transfer slots??? If it happens with the choke on, then smooths out when it kicks down, you may be into the transfer slots... Check them and spray and blow them out with cleaner and compressed air...
Also make sure that the air bleeds are not blocked...
When you sprayed the WD-40 on the idle screws and the idle smoothed out, reminds me of the days when they changed the head gasket on the 2.0 L engine from composite to MLS....
The composite gasket was more tolerant of tool marks on the head face of the block and head. When they changed to the multi layered steel gasket, if the tool marks would get too rough, they would fill the long block air test loop with rejects and back up the line. So they would soak the head gaskets with oil to fill the gaps on the mating face(s) and they would pass the air test and get the line running again. Meanwhile they could go the block or head line to adjust the head face mill cutter for a better finish and get the improved parts into the system...
Thanks for the help and replies guys.
AJ in the videos the vac adv is hooked up to the timed port on pass side. I took the 1st video with engine cold.
Surges more at idle compared to driving. But it still happens in both scenarios. In both cases, when I give it more fuel it seems to stop temporarily.
I just finished cleaning carb and checking float level and drop. They were both close to factory specs. 7/16 float level and 1 1/8 float drop.
I hooked choke up to 6V lantern battery and it didn't appear to do anything? Would it need 12 to even move slightly?
I will reinstall carb and report back.
Thanks all. Keep the suggestions coming.
AJ in the videos the vac adv is hooked up to the timed port on pass side. I took the 1st video with engine cold.
Surges more at idle compared to driving. But it still happens in both scenarios. In both cases, when I give it more fuel it seems to stop temporarily.
I just finished cleaning carb and checking float level and drop. They were both close to factory specs. 7/16 float level and 1 1/8 float drop.
I hooked choke up to 6V lantern battery and it didn't appear to do anything? Would it need 12 to even move slightly?
I will reinstall carb and report back.
Thanks all. Keep the suggestions coming.
TrailBeast
AKA Mopars4us on Youtube
#86 was the jet size, but follow AJ's advice first.
A couple of jet sizes up or down don't usually cause the problems you are having.
Trying to set choke as per manual. Heres pics from manual and a spare choke Im using for reference pics. Im using the small copper wire as the 0.026" thick gauge they call for in the instructions to slide in between piston and I have no idea how to do this?
Thanks!
Thanks!
65Val
Average Length Member
Steve....set the choke by ear. The manual is a compromise setting. Your enginwill run best with the setting it wants....Start it cold, without the air cleaner installed...open and close the choke butterfly by hand and see where your engine runs best. You can also adjust the butterfly by bending the rod in the pic below.....
-
