glhx
Well-Known Member
They are too long......I’m closing them down to square
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318 Engine stumble
- Thread starter glhx
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glhx
Well-Known Member
The electronic distributor I’m thinking about using
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glhx
Well-Known Member
Set the timing at 12° advanced
Idled the mixture screws to 21” vacuum
Closed off the secondary transfer slot
Opened the primary transfer slots to a square pattern.
My actron tachometer only goes to 2000 so I could not get total timing
Dwell is at 42
I have not test driven yet
So far I gained 2” of vaccum
I’m on 87 octane and not pinging
I don’t know if the flat spot is gone yet
Maybe tomorrow I’ll mess with it.
I did not adjust the points yet.
Idled the mixture screws to 21” vacuum
Closed off the secondary transfer slot
Opened the primary transfer slots to a square pattern.
My actron tachometer only goes to 2000 so I could not get total timing
Dwell is at 42
I have not test driven yet
So far I gained 2” of vaccum
I’m on 87 octane and not pinging
I don’t know if the flat spot is gone yet
Maybe tomorrow I’ll mess with it.
I did not adjust the points yet.
nm9stheham
Well-Known Member
Your secondaries are too far open, and the high vacuum is sucking mixture and ari through them at idle. Close them back down, but make sure the butterflies are not touching the bores. Being adjusted to 'look like a square' is just a starting point; adjustment up or down from there is common.
In your driveway, where this is acting up, the carb will be operating just on the primaries, and is going through the progressives (or transition slots) when this happens. If it is not ignition related, then I would first check float level and then pull off the meter block and clean it out; there may be some crud in the idle wells.
Once the secondary stop screw is changed, see how far your mixture screws are opened; 1-2 turns is 'normal'.
BTW, I see you have a points distributor. If the points have closed up (due to rubbing block wear is a common cause), then it will show this symptom of low RPM stumble. Adjust the points gap to to be about .017" open at maximum opening. (Or for proper dwell angle of 31-32 degrees if you have a dwell meter.) If the points' rubbing block has not been properly lubricated and has worn down the 'pointy nubs' on the octagonal cam, then you can adjust the points gap all day long and it will never be right.
In your driveway, where this is acting up, the carb will be operating just on the primaries, and is going through the progressives (or transition slots) when this happens. If it is not ignition related, then I would first check float level and then pull off the meter block and clean it out; there may be some crud in the idle wells.
Once the secondary stop screw is changed, see how far your mixture screws are opened; 1-2 turns is 'normal'.
BTW, I see you have a points distributor. If the points have closed up (due to rubbing block wear is a common cause), then it will show this symptom of low RPM stumble. Adjust the points gap to to be about .017" open at maximum opening. (Or for proper dwell angle of 31-32 degrees if you have a dwell meter.) If the points' rubbing block has not been properly lubricated and has worn down the 'pointy nubs' on the octagonal cam, then you can adjust the points gap all day long and it will never be right.
glhx
Well-Known Member
It does run better this way. The secondaries are closed down now. They barely touch the bores so as to not bind up. I seared them down all the way and lifted them just barely off the bore.
The primaries were returned to the square pattern and I never had to adjust the fast idle or the transfer slots. They are sitting at the square pattern now.
Mix screws are as you say. They were turned out 1 1/2 turns to base adjust them and turned in until the vacuum signal was highest.
I opened up the metering block and found the carb to be really clean.
All the jest and idle passages were really clean.
Will adjust the points next and check the rubbing block..
This has not been done yet.the rubbing block has never been lubricted that I know of.
The dwell was tested with a swell meter and showed 42 as opposed to the 32 you showed.
Will test drive it soon and see if that stumble is gone.
The primaries were returned to the square pattern and I never had to adjust the fast idle or the transfer slots. They are sitting at the square pattern now.
Mix screws are as you say. They were turned out 1 1/2 turns to base adjust them and turned in until the vacuum signal was highest.
I opened up the metering block and found the carb to be really clean.
All the jest and idle passages were really clean.
Will adjust the points next and check the rubbing block..
This has not been done yet.the rubbing block has never been lubricted that I know of.
The dwell was tested with a swell meter and showed 42 as opposed to the 32 you showed.
Will test drive it soon and see if that stumble is gone.
nm9stheham
Well-Known Member
31-32 degrees is the specified dwell angle. The longer dwell angle is the result of the points gap being smaller than it should be. So that is very likely contributing to the issues.
BEWARE that the points rubbing block takes a specific type of grease. Use just any sort of grease and it may wear the nubs down in a big hurry and ruin the distributor. Lithium grease will destroy the nubs... ask me how I know! LOL
Do a Google search for 'grease for ignition points'; perhaps someone here knows it off the top of their head.
BEWARE that the points rubbing block takes a specific type of grease. Use just any sort of grease and it may wear the nubs down in a big hurry and ruin the distributor. Lithium grease will destroy the nubs... ask me how I know! LOL
Do a Google search for 'grease for ignition points'; perhaps someone here knows it off the top of their head.
glhx
Well-Known Member
Wow......didn’t see that coming
Special grease. Thank you......wouldn’t have thought of that
So with 42 angle they are really stating closed for too long ?
The points should be openend up some?.....I’ll adjust them to spec.
Or the .017 you specified As a base setting.
Then run them in with the dwell meter to 32.
Special grease. Thank you......wouldn’t have thought of that
So with 42 angle they are really stating closed for too long ?
The points should be openend up some?.....I’ll adjust them to spec.
Or the .017 you specified As a base setting.
Then run them in with the dwell meter to 32.
nm9stheham
Well-Known Member
Yep... that will at least get that part in the right spec. If you get the chance, measure the maximum gap of the points before you adjust them... just for info.
Also, look at the gap and make sure there are no little metal tits on either side. If so, a VERY fine file is used to smooth them.... you used to be able to buy 'points files' for just such a purpose.
Also, look at the gap and make sure there are no little metal tits on either side. If so, a VERY fine file is used to smooth them.... you used to be able to buy 'points files' for just such a purpose.
Dwell is the degrees the points are closed. at 42° they are closed too long as nm9 suggests.
glhx
Well-Known Member
If I readjust the points.
Will I need to retime the engine?
Will I need to retime the engine?
Yes. Readjust to 28-32*, then readjust the timing. My guess will be that it will want more timing than 12* initial. Mess around with it. Give it 16, then 18.......I've already said this once. I'm startin to get blue. The engine will pretty much tell you how much initial timing it wants. As long as the idle goes up as you advance, it wants more. But you will have to find a happy medium where it does not spark knock and where it does not lug the starter cranking when warmed up. For example, I have my 1975 Ford F250 with a 351M sitting at 20* initial with a total of 34* in by about 3500. Yours is lighter, so it can stand the total to be in sooner.
glhx
Well-Known Member
How do these look?
glhx
Well-Known Member
Points were set with the feeler gauge at .017
Dwell stayed at 42
Flat spot is still there
Dwell stayed at 42
Flat spot is still there
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glhx
Well-Known Member
With the car at operating temperature.
I can slowly press on the gas.
As soon at it hits 1200 rpm it starts to surge.
When it hits 1600 the surging goes away. Maybe because the main jets take over?
We looked at the accelerator pump. It seems like it’s coming in late when flooring the gas pedal. The stumble starts and then the squirt happens right after.
When it hits the 2000 rpm above. Slowly raising the gas. That’s about the time the main start to kick in.
With the car off. The accelerator seems work just fine and seems to pump enough fuel.
Basically .....between 1100 and 1600 rpm there is a flat spot
When driving it the car just dies when I hit the gas to give it some power. If I feather it I can get through the dead spot and it’s fine.
It did backfire out the intake 1 time when I just floored it from idle.
I can slowly press on the gas.
As soon at it hits 1200 rpm it starts to surge.
When it hits 1600 the surging goes away. Maybe because the main jets take over?
We looked at the accelerator pump. It seems like it’s coming in late when flooring the gas pedal. The stumble starts and then the squirt happens right after.
When it hits the 2000 rpm above. Slowly raising the gas. That’s about the time the main start to kick in.
With the car off. The accelerator seems work just fine and seems to pump enough fuel.
Basically .....between 1100 and 1600 rpm there is a flat spot
When driving it the car just dies when I hit the gas to give it some power. If I feather it I can get through the dead spot and it’s fine.
It did backfire out the intake 1 time when I just floored it from idle.
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nm9stheham
Well-Known Member
Those points look very worn and may be working but IMHO are essentially shot. The curvature on the points contacts is all gone. I'd get some N.O.S. ones and start over. And then set the gap for the dwell to be in the low 30's. Wear on the nubs and in the shaft bushings can be contributing to all of this. With the wear on the points, it may be time to start thinking about a different/new distributor. IMHO, there are a few areas that need work.
OK on the accelerator pump; thoughts. But if you raise the RPM's really slowly the accelerator pump plays little or no role. And if by 'feathering', you mean that you give the throttle a series of small pumps, then that means the accelerator pump is being worked to cover the flat spot. I have not gone through all the past posts.... have you checked the float level? A low float would cause problems like, or similar to, this. Same thing for the secondary stop screw adjustment being off. (Which you have been adjusting.)
OK on the accelerator pump; thoughts. But if you raise the RPM's really slowly the accelerator pump plays little or no role. And if by 'feathering', you mean that you give the throttle a series of small pumps, then that means the accelerator pump is being worked to cover the flat spot. I have not gone through all the past posts.... have you checked the float level? A low float would cause problems like, or similar to, this. Same thing for the secondary stop screw adjustment being off. (Which you have been adjusting.)
glhx
Well-Known Member
The secondary stop is closed....and just barely cracked so it’s moved off the bore.
The float is just barely tricking out of the side when I take the plug out so it should be good.
The primary transfer slots have been adjusted correctly.
The transfer slots are supposed to work from 800-1600 rpm. Maybe the problem is in there because that’s the rpm range that the problem happens. However. The idle bleed and the idle well feed the transfer slots as well. It would have to be just transfer slots that were clogged. The fault spot seems to be in the transition.
What would a worn distributor cam cause? It would keep the primary windings in the coil to charge up longer and breaks the field later than it is supposed to? If this is the case. Would it show up at lower and higher rpm? How much of a problem does 10° Higher Of dwell cause? I could put the electronic distributor on there but it’s a learning experience to see what problmems lead to what.
The burned points could be a bad condenser not absorbing the arc at the opening of the points? I kind of looking for the understanding of why just to learn.
Could a vacuum leak happen at this rpm range? Why wouldn’t it affect higher rpm where it seems to have plenty of power?
The float is just barely tricking out of the side when I take the plug out so it should be good.
The primary transfer slots have been adjusted correctly.
The transfer slots are supposed to work from 800-1600 rpm. Maybe the problem is in there because that’s the rpm range that the problem happens. However. The idle bleed and the idle well feed the transfer slots as well. It would have to be just transfer slots that were clogged. The fault spot seems to be in the transition.
What would a worn distributor cam cause? It would keep the primary windings in the coil to charge up longer and breaks the field later than it is supposed to? If this is the case. Would it show up at lower and higher rpm? How much of a problem does 10° Higher Of dwell cause? I could put the electronic distributor on there but it’s a learning experience to see what problmems lead to what.
The burned points could be a bad condenser not absorbing the arc at the opening of the points? I kind of looking for the understanding of why just to learn.
Could a vacuum leak happen at this rpm range? Why wouldn’t it affect higher rpm where it seems to have plenty of power?
nm9stheham
Well-Known Member
Agreed on the transition. That is why to look at the float, secondary slots, etc. They all sound good. But crud in the wells, air or main jets, or even cracks in the metering body can upset all of that.
Now go back to post #2. That suggests looking at the vacuum secondary control. If the spring in the vacuum pod is weak or someone put in a really light spring, it can open prematurely.
A weak spark will also cause odd flat spots; certain fuel-air mixtures and operating conditions require more spark energy and a weak system can make it fire OK under some conditions but break up under other. So you gotta keep plugging through all of the ignition parts.
You are right to suspect the condensor; it takes specific equipment to test. Easier to just replace.
It don't recall your coil or anything. If you have a voltmeter with ohmmeter, do the following:
- In ohmmeter mode on the lowest scale, touch the leads together directly a few times and take note of the average resistance of the leads.
- Disconnect one side of the coil and measure resistance between the coil + and coil -; subtract the lead resistance and it ought to be around 1.5 ohms for a sotck type coil
- Disconnect one side of the ballast resistor and measure across the terminals; subtract out the lead resistance and for a stock ballast, it ought to be around 0.6 ohms.
Worn distributor cam means you can't the gap and dwell relationship right; if you open the gap on a worn cam, then the dwell gets too short and you can't get the coil charged. Too much dwell or too small of a points gap mans the points don't open far enough to get a proper spark discharge. (Same for too small of a gap...)
You seem to have an odd situation there; right gap.... but long dwell. The more I think about it, I can't wrap my head around why unless it is worn shaft bushings and that is throwing off the gap measurement.
Now go back to post #2. That suggests looking at the vacuum secondary control. If the spring in the vacuum pod is weak or someone put in a really light spring, it can open prematurely.
A weak spark will also cause odd flat spots; certain fuel-air mixtures and operating conditions require more spark energy and a weak system can make it fire OK under some conditions but break up under other. So you gotta keep plugging through all of the ignition parts.
You are right to suspect the condensor; it takes specific equipment to test. Easier to just replace.
It don't recall your coil or anything. If you have a voltmeter with ohmmeter, do the following:
- In ohmmeter mode on the lowest scale, touch the leads together directly a few times and take note of the average resistance of the leads.
- Disconnect one side of the coil and measure resistance between the coil + and coil -; subtract the lead resistance and it ought to be around 1.5 ohms for a sotck type coil
- Disconnect one side of the ballast resistor and measure across the terminals; subtract out the lead resistance and for a stock ballast, it ought to be around 0.6 ohms.
Worn distributor cam means you can't the gap and dwell relationship right; if you open the gap on a worn cam, then the dwell gets too short and you can't get the coil charged. Too much dwell or too small of a points gap mans the points don't open far enough to get a proper spark discharge. (Same for too small of a gap...)
You seem to have an odd situation there; right gap.... but long dwell. The more I think about it, I can't wrap my head around why unless it is worn shaft bushings and that is throwing off the gap measurement.
glhx
Well-Known Member
I’m going to go through the carb and blow out all the air bleeds and wells. All the ports on the primary and secondary. One thing I have not adjusted on this used carb is the accelerator pump. I went though and memorized the Holley flow diagram so I have a good idea where and how it’s working.
Then test the coil and ballast resistor like you said. The coil is a blaster 2 msd and the ballast resistor is new so they both should be good. Neither have even 100 miles on them.
Could a bad condenser cause a high dwell?
As far as the dwell goes. What about skipping the feeler gauge and just opening the points up until the dwell hits 32.
What I’ve been doing is adjusting them. Putting the whole thing back together and idling the car. The dwell shows 41 at .017.
So maybe open them up to .020 and see what that does.
The cam block doesn’t look worn but I don’t know how to get spec or tell. The distributor is old 1968 and may be original to the engine.
I do want to put the elsectronic set up in but I want to understand these points. The shaft play seems fine
Then test the coil and ballast resistor like you said. The coil is a blaster 2 msd and the ballast resistor is new so they both should be good. Neither have even 100 miles on them.
Could a bad condenser cause a high dwell?
As far as the dwell goes. What about skipping the feeler gauge and just opening the points up until the dwell hits 32.
What I’ve been doing is adjusting them. Putting the whole thing back together and idling the car. The dwell shows 41 at .017.
So maybe open them up to .020 and see what that does.
The cam block doesn’t look worn but I don’t know how to get spec or tell. The distributor is old 1968 and may be original to the engine.
I do want to put the elsectronic set up in but I want to understand these points. The shaft play seems fine
glhx
Well-Known Member
Rechecked thenpoints again. I was hooking upmthe dwell meter wrong.
I had the negative side of the coil hooked up right. The ground side I had hooked to positive.
When hooking it up right. Negative side of the could and the other lead to engine ground.
.017 gave me 15° dwell.
I had the negative side of the coil hooked up right. The ground side I had hooked to positive.
When hooking it up right. Negative side of the could and the other lead to engine ground.
.017 gave me 15° dwell.
You can still buy points files at NAPA. Bought one there recently.
I finally gave up on points in my old Willys and converted to electronic, could not find a condenser that would last, tried several different brands, all were either junk out of the box, or gave me running issues.
I know I still have a decent small block single points distributor, PM me.
I finally gave up on points in my old Willys and converted to electronic, could not find a condenser that would last, tried several different brands, all were either junk out of the box, or gave me running issues.
I know I still have a decent small block single points distributor, PM me.
glhx
Well-Known Member
The raising of rpm also causes a surge.
I’m wondering if the throttle blades have an air leak.
How can you diagnose something like that
To get the dwell to 27° I had to set the points at like .010
The points would not close any more than that on the distributor cam high spot
I’m wondering if the throttle blades have an air leak.
How can you diagnose something like that
To get the dwell to 27° I had to set the points at like .010
The points would not close any more than that on the distributor cam high spot
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nm9stheham
Well-Known Member
Can you post pix? It would be good to see the nubs on the distributor cam. It sounds like the are worn. The coil won't get a good charge each cycle with too small of a dwell.
BTW, on the ballast, checking the resistance value is wise. There a quite a different number of ballasts and most are wrong for the Mopar system, points or electronic. It uses lower resistance values for the coil and ballast resistance than many other systems.
For the blades having a leak, I assume you mean by the throttle shafts. That usually makes the idle speed erratic. But you can spray something mildly combustible on the shafts on the outside and see if the idle speed jumps up.
BTW, on the ballast, checking the resistance value is wise. There a quite a different number of ballasts and most are wrong for the Mopar system, points or electronic. It uses lower resistance values for the coil and ballast resistance than many other systems.
For the blades having a leak, I assume you mean by the throttle shafts. That usually makes the idle speed erratic. But you can spray something mildly combustible on the shafts on the outside and see if the idle speed jumps up.
glhx
Well-Known Member
I believe this is sitting @.017 right now.
nm9stheham
Well-Known Member
I'd like others to comment but they look worn to me. Especially in the bottom pix. Like the sharpest part of the nub is worn off.
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