318 Engine stumble

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I will get more pictures of it.
And pictures of what the gap looks like when it’s at its highest point set at .017

What would the outcome of such a small dwell cause?
The points would not stay closed enough to sufficiently charge the coil.......causing a weak spark?

And too much dwell keeps them closed too long. When They are not open long enough it affects the time allowed for the magnetic field collapse into the secondary windings. Not giving it enough time to collapse and generates a weaker spark?
 
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Correct on the short dwell.

The too long dwell may be due to what you say.... or it may be associated with the points not opening adequately, and not making a clean break and the spark may be effected by some continued arcing across the not-well-opened points.

8 cylinders are the hardest.
 
I went into the carburetor and cleaned out all the jets and bleeds with compressed air and carb cleaner

Readjusted the accelerator pump. It seems to be better

The problem off idle is still there. A huge surge that makes the engine shake. While this is happening. I looked down the carb.

The transfer slots are putting gas in there at the right time. The spray evenly.

The idle vacuum is still 21”

When I floor it. The bog seems to be gone as the accelerator pump seems to be doing its job there.

When I slowly raise the gas. THe accelerator pump does nothing. The transfer slots seem active until the main jets start working.

When the main jets start working the problem seems like it’s gone

I checked the diaphragm in the accelerator pump and the check valve inlet. They are fine.

I sprayed around the base of the carb with cleaner when the problem occurred and no change. I sprayed down into the carb when it occurred and no change.

When driving. I can floor it and the huge flat spot is gone. Now there’s just the surge and when I power through it quickly all the power is there as the main jets take over.

When hitting the throttle fast. The accelerator pump is working

I do have a video of the surge. It’s is off idle until the main jets take over.

The carb jets are 62

The vacuum gauge says 14 when the problem starts
 
It sounds like a good diagnosis. Raise the float level a bit and retune the idle mixture and then see if issue gets better. A higher float level generally generally will make the transition circuit richer. Also, look at the top area around the primary bores, and look at the air bleed there are 2 on each side. Make sure that none of the air bleeds have been drilled open. If the idle air bleed has been drilled out, it will lean out the transition circuit.

Also I am a bit baffled why the accelerator pump does nothing when opening the throttle slowly. When you say check valve, have you checked the little weight and check ball under the pump nuzzle itself? When not running, just a slight movement of the throttle off of the idle stop ought to produce a dribble from the nozzles.

BTW, what Holley List # do you have?

The engine is likely at it's leanest when this occurs, and the mixture may be harder to fire. So, if the ignition still has these odd dwell issues, it may be time IMHO to put in the other system and see if that improves this.
 
It’s seems like there is excess air coming in just as the transfer happens. I watch the surge happen when the transfer slots are working.

I’ve been pointed to the accelerator pump. I’ve ruled it out as its adjusted well. The problem only happens during transfer and I’m getting fuel the entire transfer. I don’t think it’s lack of gas.

But where would air be co I g from just in this one area of throttle position. Good vacuum shows no intake leak.

Can the intake or vaccum have a leak just in transition alone.
 
It’s seems like there is excess air coming in just as the transfer happens. I watch the surge happen when the transfer slots are working.

I’ve been pointed to the accelerator pump. I’ve ruled it out as its adjusted well. The problem only happens during transfer and I’m getting fuel the entire transfer. I don’t think it’s lack of gas.

But where would air be co I g from just in this one area of throttle position. Good vacuum shows no intake leak.

Can the intake or vaccum have a leak just in transition alone.
 
I’ll go ahead and finally put the electronic one on there.

I found it strange the accelerator pump did nothing.
I’ll recheck that. Go ahead and take the discharge nozzles off and look in there.

When I give it gas I get plenty of pump shot.
I do wonder about something

The pink cam seems to not engage the accelerator pump arm at all off idle.
I’m not sure how this is supposed to work exactly.

Maybe I’ll manually work the accelerator pump arm
 
The different cams (different colors) engage the pump arm at different amounts and at different times in the throttle movement; and you can flip the cam over and screw them in at the different holes in the cam to change the curve too. You can do a lot of customizing of the pump curve versus throttle position.

Here is a chart, which shows that the pink cam can have no pump shot just off-idle in certain positions, and can the slowest one to come in as you open the throttle when mounted in certain positions. IIRC the orange one is the typical one you get new but one position of the pink one is pretty close.
Holley accelerator pumps/cams | Grumpys Performance Garage

If there is a small gap between the pump arm and cam at idle position, that can be closed up and you should get a bit of dribble with any amount of throttle movement.
 
Something else to note.

Even when the throttle is held steady.
I look down and see the transfer slots working. Spraying a nice shot of fuel very steady.

With the throttle held in one place like this. The accelerator would be done doing its job.

The surge is constant even when holding the throttle like this. The orange cam I think will help. I don’t think the problem is in the accelerator pump due to this reason.

I will raise the float some so gas is trickling out with the car running.

The reason I haven’t put the electronic on yet is when I did the first time it didn’t work.
I know it has to because I drove the donor car into the shop to remove the engine.

It’s the 5 pin dual ballast set up from 1976 charger. Might as well try it again.

I appreciate you sticking with me on this. I’ve learned a lot so far.
 
Even when the throttle is held steady.I look down and see the transfer slots working. Spraying a nice shot of fuel very steady.

The surge is constant even when holding the throttle like this.

I will raise the float some so gas is trickling out with the car running.
OK the float change is just a test, to see if richer makes things better. Or worse.

Is the fuel coming out of the transfer slots in the bottom of the throats, by the throttle blades? Is it liquid? If so, that does not seem right.... it ought to be an 'emulsion', which is a a fine mix of air and fuel. If it is liquid fuel, then now I would think the idle air bleeds are plugged up....

Have you looked at your plugs ?

Not sure if I am really doing you much good!
 
Yeah.....I looked at the plugs. They are a nice golden brown.

I put a rag over the secondaries and the car about died.
I set the secondaries according to a spec. Seat the blades and turn half turn out. Me not having a lot of experience with carburetors.....I just did what it said.

However.......the cracked the blades too much and allowed a lot of air to come in. I closed them up a lot more. Now you can barely see out of them when holding the carb up to the light.

This helped considerably. It did not take care of it. But the car doesn’t die out when I hit the gas now.

Adjusting the accelerator pump yesterday helped. There is no slack at idle. But it’s also not pushing the pump arm down. This helped with response and I feel good about this adjustment.

The idle screws are turned 1 turn out. Turning them another half out did nothing.
It didn’t affect vaccum at all.

I plugged off the vacuum advance port. I then tested the diaphragm on the advance and the vacuum bled off. I will run a tighter seal on it but I think the vacuum advance MIGHT have a hole in it. Plugging it off did nothing to help with the surge. I was hoping it would.

I also plugged off the auxiliary vacuum port. It helped some.
The vaccum seal to my performance flapper on the air cleaner wasn’t tight enough. I replaced that vacuum line...... Very little change the idle went down and I readjusted the screws .....the vacuum is still pulling 21”.


I did mock up the electronic distributor today. Should be in soon. I found a connection where the clamp on a terminal end was clamped to rubber casing on the wire. This might be why it didn’t work the first time. I have the tool to run the packaed clamps so I fixed that with a factory connection. Hopefully the distributor will work this time. I might mock it up and test it before putting it in.

The throttle response is excellent. I hit the gas and it burns the tires. The more I drove it however. The less performance it had. When my friend rode with me. Power went down and I ran into the surge more. He weighs a lot.

The surge is still there. Not nearly as pronounced but it’s still there and starts right off idle.

I looked at the accelerator pump again. The do come out when I slowly push on the gas. Not a lot though.

It seems to be getting better and better the more I mess with it.

My brake booster is hooked directly to the intake. It tees off to the Pcv valve. Actually.......I just thought about it.....shouldn’t that go into the carburetor base?

All that is left is the intake gaskets and the distributor.
But wouldn’t an Intake gasket affect idle. Idles good at 700rpm.

What a weird deal.

The transition slots are emulsified fuel. The bleeds were sprayed very well with carb cleaner and I saw a nice pattern out of all of the,

Then they were sprayed with compressed air. I felt the stream. I’ve got the carb flow and understanding memorized now so when I was spraying all of it out I knew exactly which ports when where and what affected what.

I’ll post pictures of all I found today.
If this was a built engine I could understand some of the components not working.....like a 62 jet and a pink pump cam.

But since it’s stock and not built at all. I would think all this stuff would be fine. The orange cam might be better.
 
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All I can add is yes, the PCV goes to the carb base. I doubt it is causing the issue.

BTW, what idle vacuum level do you have?
 
I’ve been messing with this again. The problem is still there.

The only thing to concentrate on is pulling the throttle to right off idle position and holding it there.

THe transfer slots are going full force. I can look down and see them working. The engine is stumbling here. They are air and fuel. A fine spray.

The accelerator pump would not be doing anything.
The power valve would not be engaged because
........The engine is held by me to a position of right off idle.
The only circuit that would be working is the transfer circuit because the accelerator pump has done its job.

Where could extra air be coming in. The vaccum ports are all blocked off.

Could it come into the intake or
.....power brake booster connected straight to the intake.
Pulling in extra air as the throttle opens up and air velocity is increased.

If that’s the case. Wouldn’t idle vacuum be really low. 21” is a pretty high number.

It seems like this problem is extra air coming inrifht off idle into the transfer circuit .
It might be masked at idle by tuning it out and pulling enough gas at higher rpm to mask it there as well.


Could an intake leak cause a problem like this?
 
Or the transfer circuits are too rich. But you said you blew out the air bleeds.

I would adjust the float up and down while you do the same thing and see if it changes; that float adjustment will effect the richness of the mixture out of the transfer slots.

Did the new distributor get in there? I'll keep saying.... it can be ignition too. The spark voltage needed to fire the compressed fuel-air mixture varies. You just may be in an operating region where the mixture it harder to fire, and a weak ignition will show up under those conditions.

Did you ever post the measured resistance value of the the ballast?
 
I would change the points and condenser with a good set that also has high spring tension IE Blue streak. See if the mechanical advance is sticking also just turn the assy the rotor sits on it should move a bit with no binding.
 
Can I butt in?

How about this;
A) First; make sure that the firing order is correct, and your compression is fairly even, and the gas is fairly fresh, and the condenser is seeing battery ground , and that the PV is not leaking, and that the coil is seeing at least 6.5 to 7.5 volts while running; by 5.5 volts the ignition will crap out.

B) Then crank up the speed screw until it complains. Then slowly close the choke. If the engine cleans out, then you know it's sucking air,or not getting enough gas.Figure out which and fix it. But if it doesn't clean out,or gets worse; go to E); otherwise

C)To determine which is causing the lean-running, run the engine up to the crap-zone, and put a clamp on the the fuel supply line, then wait.
One of three things will happen;
1) the engine will run worse and worse and finally stall
2) the engine will start to run better as the fuel runs out, then after a long time, switch to running like #1
3) the engine will start to run better, but then almost immediately switch to running like in #1
#1 means the fuel level is too low, #2 means the fuel level is very much too high. #3 means it is pretty close, move on.

D) Once that is sorted, and it's still not right, you are gonna have to figure out how the extra air is getting into the intake.The first thing I do when I get a difficult case is to put a vacuum/fuel pressure gauge on the dipstick tube,and flip the pcv out of the valve cover, and seal the engine up tight. Then start her up and idle her up to the crap-zone again, while watching the gauge. There is no way the engine should pull a vacuum on that gauge. In fact, pressure should slowly start to build. Shut the engine off before it exceeds about 4psi, to prevent blowing a seal. If yours works like that, then you're gonna have to search harder for an external leak. Clamp or disable every vacuum line that you can find,one atta time,while the engine is idling in the crap-zone. Then move to the intake ports, then the carb base, and finally the throttleshafts. Use a checking fluid that makes a difference when you inject it directly into the primaries. I use a product called Brakleen cuz when it goes thru the combustion chamber and comes out the tailpipe it will make your eyes water and burn you nose. I don't recommend it to you cuz that's a poisonous gas, and I don't know what it will do to your brain.My brain is old so I don't care. Pure oxygen works too with no side effects,lol.
But if it pulls a vacuum,then the intake has to come off.

E1) But if it doesn't smooth out, on the choke-test;
Open the choke back up, and adjust the mixture screws to whatever she likes best,
EDIT; see post #71, for E2
And if that don't do it disconnect the Vcan.
If that makes it worse, hook it back up, and start adding timing by rotating the distributor until she smooths out, WITHOUT regard to any number, just pull on it until she smooths out.
If she smooths out, then idle it back down to 700, and now put the light on it. If the idle timing is more than 25*, you are gonna have to synchronize your piston TDC to your balancer mark.
If TDC =TDC, then you are gonna have to check your cam lobes and/or cam-timing.

F) when everything is perfect but it still wont smooth out, check that your balancer is correct for your engine,and that the TC weights are where they should be,

Tips
As to the points,
If you can get 28 to 32* dwell with a gap in the range of 15 to 19, you are good at least for diagnostic purposes,so long as they break cleanly. That means the contacts should be CLEAN, flat and uncontaminated and that the condenser is preventing arcing. To prove this, you can run the coilwire to near ground, and pop the cap off. Then have a helper crank the engine while you observe both the coil wire for a steady stream of sparks, and also watching the points which should have little to no sparking.
As to the accelerator pump, you have to reset or at least check the linkage after every time you change the transfer slot opening.
As to the PV; if you have a Holley. I suggest you pull yours out and install a PV-plug for testing purposes.
As to the PCV, it should be routed to the carb base, usually the front
As to the booster, it can be routed to directly to the intake.
As to the EGR, if your manifold has a plate, make sure it's sealed.The floorjets can remain in the bottom of the plenum floor no problem.
Wires; make sure they're all fully connected on both ends
MJs, if you have headers and dual exhaust, I think those 62s are gonna be too small, but right now, they are not an issue.
That's all I got, Happy HotRodding
 
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I believe
That is totally a low-speed delivery problem, so I'm adding this to my previous post, #69 .But first disable the Vcan and repeat the test. I want to be sure your vacuum advance system isn't involved.If no difference is noted then let's continue;
E2) The low speed system consists of; 1) the fuel level,and 2) the transfers,and 3) the pilots,AKA the idle mixture screws,and 4) the Idle air bleeds, and 5) yje gaskets I guess,lol. One of these is gonna be the problem. And probably not #1.
So we are gonna need to separate the transfers from the idle mixture screws. To do that,it's easiest to prove the mixture screws are working first.
So;Idle it down to 650 or as low it will go. Make sure the secondaries are fully closed but not sticking.Put about 12 to 14 degrees of idle timing into it, then Idle it down to 600. If you can't get 600/650 there is a problem in the pilot system. So idle it down as far as it will go and let's continue. Pick a mixture screw and start cranking it in until the engine wants to stall then give her enough juice to keep her running. Then start screwing in the other one, the same way, and again add a bit back out. Now Firstly, they better both make a difference and they better both want to make the engine want to stall. Then shut the engine off then go count the turns of each screw and they better both be close to the same.If the screws end up within 1/2 turn of each other and the number is between two and three turns out, I would consider that normal. Now put them both back to 1.75 turns.
Ok but if one of them falls outside this range; We are gonna have to figure out if the mixture passage is at fault or if it's an air-bleed. So
Crank her up, and keep her running. Then from under the hood, we are gonna vacuum out the bleeds. So rev her up to 2200 and slam the choke closed. Just before she stalls open it back up and let the revs climb back up. Repeat two more times. Then see if she still runs like crap. If she's smooth now, congratulations, the engine sucked the dirt out of the bleeds.. But If no difference then it has to be in either the transfers or in the idle well.
So idle her up into the crap-zone and screw the mixture screws all the way in, one atta time. Do they both make about the same no-difference? It doesn't really matter to me cuz by this time I'm sure that the metering block has a problem. It's gonna have to come off for a more thorough inspection and cleaning.
The above assumes the PV is not leaking, through the diaphragm, and I touched on that in #69.
I think I got the bases covered,lol.
 
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Have some more info. I took more video of mixture screws and how they are affecting everything.

I will say that I ran the timing up to 15° and the engine really liked it. Went to a solid 21 1/2” vacuum.

The mixture screws like to be 1 turn out. I’ll go more into this.

The reason I posted was.
Vacuum advance. I put a better seal on my vacuum gauge and
re-tested the advance canister. It held vacuum just fine.

I took off the brake booster and sealed up all vacuum accessories.
The carb is isolated.

Huge problem is in the advance. I plugged it in and that’s where a whole lot of the stumble is coming from. When I unhooked it. It revved a lot better. 3/4 of the stumble is gone.....

The mechanical weights or the vacuum advance mechanism must be seized up.

The engine sounds more crisp but the stumble is still there some.
I’m closer than I was. Starts at 14-2000 and is really there around 1700.


Power to the coil.......is 9v

Resistance across the ballast resistor is 1.5 ohms.

The ballast resistor for the electronic distributor........
the dual ballast....also 1.5ohms on both

I will post more tomorrow.

One of the idle mix screws has some gas on it. Not much but some. It’s leaking there on the drivers side.

I will take it for a test drive to see where I’m at.
The distributor has to go. I wanted to learn points ignition system
and I think I have enough info on that now.

What would be a good recommendation for a distributor for a replacement. I only want around 300hp max out of this engine so nothing really tricked out.
 
Power to the coil.......is 9v

Resistance across the ballast resistor is 1.5 ohms.

The ballast resistor for the electronic distributor........
the dual ballast....also 1.5ohms on both
Did you test the resistance of just the meter leads and subtract that out? If not, then the readings may be high; ballast resistance is very low, in the same range as lead resistance, so you have to do that.

If you did compensate for the meter lead resistance, and 1.5 ohm is indeed the correct reading, then you have the wrong ballast. The stock Mopar single ballast should be 0.5-0.6 ohms cold for both points and electronic systems.

BTW the dual should be 0.6 ohms on one side and the other side would be around 5 ohms. You need to disconnect all the leads on one end of both resistor types to make sure you have valid readings, or just disconnect them all.

I would check out Stan White distributors and MSD distributors.
 
comments inside the quote
I’ve been messing with this again. The problem is still there.

The only thing to concentrate on is pulling the throttle to right off idle position and holding it there.

THe transfer slots are going full force. I can look down and see them working. The engine is stumbling here. They are air and fuel. A fine spray.Are you by any chance confusing the transfers and the mains? The transfers discharge below the blades at 1700rpm, I don't think you can see them. And at 21 inches idle vacuum,it's probably too early for the mains; they should be dead or near dead at 1700 no-load.Or are you confusing the transfers and the accelerator pump discharge nozzles; If the check plunger or ball is missing from just underneath of them, then your high vacuum can pull fuel out of this circuit.Did you once mention finding a ball after you tipped the carb over?


The accelerator pump would not be doing anything. Correction;SHOULD NOT BE
The power valve would not be engaged because........The engine is held by me to a position of right off idle. Correction; the PV SHOULD not be engaged. It discharges from the main circuit, same as the mains, so if you see the mains discharging at 1700 with no load, then it is entirely possible that what you are seeing, is a PV discharge.

The only circuit that would be working is the transfer circuit because the accelerator pump has done its job.Again; SHOULD BE

Where could extra air be coming in. The vaccum ports are all blocked off. I mentioned this once before; flip the PCV out of the valve cover and seal the covers. Then put a vacuum gauge on the dipstick tube. There should not be any vacuum there. At 21 inches idle vacuum,I doubt you have this problem.

Could it come into the intake or.....power brake booster connected straight to the intake. The booster should be plumbed directly to the intake, usually at #8 runner, and the PCV on a separate line to the front of the carb, and exits under the throttle plate there.
The Vcan line SHOULD be plumbed to the spark port, which SHOULD be dead at idle. This port will increase in vacuum signal as the throttle opens ,BUT should be dead at idle and may not begin to pull significant vacuum until 1500rpm. or higher. This action is heavily dependent on the engine load and TIMING.
I've said this before, but here it comes again;
Disable the Vcan, Crank the idle speed up into the crap-zone with either the fast-idle cam or the speed screw. Pull or push the distributor until the rpm peaks, then readjust the idle speed into the crap-zone. You now have fully and completely ruled out a timing problem. Readjust the mixture screws as may be required for best quality of idle at that rpm.Put a timing lite on it and watch the strobing, looking for dropped sparks or any monkey business going on there.
Now, grab your flashlight and shine it down into the venturies. You SHOULD NOT see any fuel discharge anywhere. The pump nozzles should be inactive and the mains as well. The only fuel flowing SHOULD be from the transfers, which you should not be able to see, as the entire slots or almost the entire slots, should be below the plates. If any portion of the slot is above the plate, it should be inactive and dry.
For the heck of it put one finger on top of each booster to destroy the signal there. The engine idle quality should not change. If it smooths out, then there is your problem.


Pulling in extra air as the throttle opens up and air velocity is increased.

If that’s the case. Wouldn’t idle vacuum be really low. 21” is a pretty high number.

It seems like this problem is extra air coming in right off-idle into the transfer circuit. To me it seems like waay too much fuel.
It might be masked at idle by tuning it out and pulling enough gas at higher rpm to mask it there as well. Masked because the transfer port exposure is really small or non-existent. Have you set your T-port sync?
Could an intake leak cause a problem like this? I don't think so
 
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What I decided to do was go with a skip white distributor. The gm hei version. I’ll start with that and then see what I can do with the timing to get it optimal

I also picked up a tachometer. I was using the actron, which is limited to 2000rpm. Can’t get total timing with that.

Should be able to adjust the mechanical with springs and vacuum advance curve with this. Will get rid of the coil, electronic box, and the ballast resistor. I’ll get a total timing of 34° @3000
And get as high a base timing as I can.

Set the plug gap to .045 and go from there.

Will go through your check list in order as well.
 
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