Pulling my hair out over this misfire

[runmikeyrun]

Ok. The truck was running great until one day a couple weeks ago it wasn’t. I had parked it for a week and went to head out for a car show that evening. It was running a little rough, but ran better when I gave it some gas. As I went down the street the missing got worse. No backfiring, just a miss that was getting progressively worse. Took it back after a 1/2 mile and the radiator was boiling over a touch (never happened before) and I had oil smoke wisping out of the oil fill tube breather.

History: It’s a Y block with Holley 4bbl and pertronix ignitor (first gen). Everything had been cleaned, rebuilt etc this winter and the truck had done about 30-40 solid miles with no issues and was running and idling Great. Pertronix is new this winter, as is all the wiring on the truck, the cap, rotor, plugs etc. The only thing I did in between the truck running fine and the start of the issue was install a 12v power port, which worked fine.

Back to the truck. Parked it and figured I lost a head gasket due to overheating. Oil and coolant ok.

Stuck thermostat contributing to overheating? Pulled housing, no thermostat in place. Changed the coolant because it was really rusty and flushed the system. Belts tight to spec. Checked the fan shaft and no play, spins freely.

The one distributor cap clip was only half on, prompting me to think the cap got loose and moved, changed the timing etc. Took off the cap- inside was chewed down (looks like the cap was a touch too short) and some fine brass shavings inside but ok otherwise. Cleaned the dizzy out, replaced the cap and rotor. Re-timed, still misfiring.

Since the cap was still loose, I figured I needed to tighten the clips. Replaced one assembly and got that side tight, but the other is pinned against the firewall and it’s still a little loose. The cap does have just the slightest amount of play but is 100 times better than it was.

Reset the timing to 10 btdc, where it was before when it ran perfectly.

Truck is still misfiring.

Cleaned all the spark plugs- many were sooty, a couple oily. Still misfiring.

Started pulling wires off the cap one at a time to isolate the bad cylinder(s) and it runs the same with pretty much any wire pulled off, the same rough idle. Didn’t seem to matter which wire I had off it still missed. Sometimes a with a certain wire off it would barely start, other times with that same wire off it still just missed. I could not isolate the problem to any single cylinder. After 8 hours I went home pissed off.


Fast forward a couple weeks. Today I came in and thinking I may have bumped a wire on that fuse block putting in that 12v power port, I checked the wire feeding the ballast resistor from the fuse box and it was loose. I plugged it back onto the terminal securely. That’ll do it! Nope. Still missing.

I figured maybe the Pertronix wasn’t getting enough voltage. Ground bad? I cleaned the dizzy base plate and ran a ground wire from the hold down screw of the pertronix to the plate. Still missing.

Checked my ballast resistor and coil resistance. Now, the resistor I ordered was 0.7 ohm and coil 0.8 ohm since the Pertronix wants to see a minimum of 1.5 ohms. I’m getting 1.6 across the resistor and 1.6 across the coil, for a total of 3.2 ohms. I’m getting 12.6v at the fuse side of the ballast resistor (which is where the Pertronix positive wire is connected) and getting 6.6v at the positive terminal of the coil. Theoretically, the coil should be ok with 6.6v since I assume the resistances of those two items are the same as before, right? I didn’t measure the coil or resistor when I bought them, so I’m assuming they were both like that.

Idle is rough. It does run smoother the higher I rev it. It’s just a dog until I get the revs up. This is very similar to how it ran before I re-timed it, cleaned the carb, did a tune up etc except I have done all of those things.

The kicker- the pass side exhaust pipe is showing evidence of burning a little oil and the driver’s is not. And every time I shut the truck off, little wisps of bluish oil smoke come out from that filler tube breather. I’m not convinced it’s related but also not convinced it’s a separate issue.


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[fordor41]

my instructions for the Pertronix igniter 1 said to supply 12V to the ignition, don't go thru the Ballast resistor.

[cousinjd]

Vacuum leak????

[40cpe]

compression check?

[Lanny]

Originally Posted by 40cpe

compression check?

============================================



And when you check compression, hold the throttle plate wide open
with something, so the cylinders can suck in air, so you get an
accurate compression reading.






.

[runmikeyrun]

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Originally Posted by fordor41

my instructions for the Pertronix igniter 1 said to supply 12V to the ignition, don't go thru the Ballast resistor.

Yup. Mine is connected before the resistor getting full 12v from ignition power


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[runmikeyrun]

Originally Posted by cousinjd

Vacuum leak????

A good thought. I’m gonna look around a little, there’s really no vacuum lines anywhere though (distributor has mechanical only, it’s a 1960 truck dizzy).

Will give the intake manifold, carb etc a good spray with wd-40 and see what happens.


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[KULTULZ]

A basic low cost vacuum gauge will most likely diagnose the problem(s), or lead you to the source.

[KULTULZ]

Originally Posted by fordor41

...my instructions for the Pertronix igniter 1 said to supply 12V to the ignition, don't go thru the Ballast resistor.

KEY WORDS SPOKEN HERE-

You also need to supply the correct VOLT to whatever coil design you have chosen to use.


The PERTRONIX I can fail if the IGN SW is left on with engine not running.

The DIST you have chosen (only mechanical advance) may have the incorrect advance curve for your application. Did you ever decide if the engine is PASS CAR or HD TRUCK?

[KULTULZ]

Originally Posted by runmikeyrun

Took it back after a 1/2 mile and the radiator was boiling over a touch (never happened before) and I had oil smoke wisping out of the oil fill tube breather.

... hmmpf ...

Just wondering, did you do the crankcase ventilation modification you posted earlier about?

Earlier Post Here - https://www.fordbarn.com/forum/showthread.php?t=245537

[runmikeyrun]

Originally Posted by KULTULZ

KEY WORDS SPOKEN HERE-

You also need to supply the correct VOLT to whatever coil design you have chosen to use.


The PERTRONIX I can fail if the IGN SW is left on with engine not running.

The DIST you have chosen (only mechanical advance) may have the incorrect advance curve for your application. Did you ever decide if the engine is PASS CAR or HD TRUCK?

I’m quite sure I have not left the key on at any time, I’m really diligent about that.

I’ll have to look into the coil, but the truck was running fine before so I think my coil setup is ok.

The block I have is 55-57, but distributor, intake manifold, and exhaust manifolds are all truck items. So not real sure LOL.

I have not performed the road draft tube modification yet that I discussed earlier, just haven’t had time.

I am going to pick up a vacuum gauge and go from there, thanks!!


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[scicala]

Use a timing light to double check that the base timing is correct. Specs say about 5 degrees BTDC, but 10 degrees works better on Y-Blocks. then with the timing light, make sure the timing is advancing when you rev the engine.
Retarded (or no) ignition advance causes very high exhaust temps and can cause overheating.


Sal

[runmikeyrun]

Originally Posted by scicala

Use a timing light to double check that the base timing is correct. Specs say about 5 degrees BTDC, but 10 degrees works better on Y-Blocks. then with the timing light, make sure the timing is advancing when you rev the engine.
Retarded (or no) ignition advance causes very high exhaust temps and can cause overheating.


Sal

Agreed, I think when the cap shifted it retarded the timing. It has since been set back to 10 btdc where it ran great.


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[KULTULZ]

Originally Posted by runmikeyrun

I’m quite sure I have not left the key on at any time, I’m really diligent about that

Just saying, the PERT I is delicate.

I’ll have to look into the coil, but the truck was running fine before so I think my coil setup is ok.

It all depends on what style coil you are using, internal or external resistor and if HP, you follow the manufacturer's instructions. It may take a while to damage a coil.

Think again about the distributor you are using. It is setup for a low RPM HT engine. It may not have correct timing curve if used on a higher RPM car or light truck engine. Improper/inadequate advance leads to over heating.

Be careful of the dist cap you decide to use. Aftermarket may be junk. You didn't have an earlier LOAD-O-MATIC cap on there did you?

[runmikeyrun]

Originally Posted by KULTULZ

Just saying, the PERT I is delicate.

It all depends on what style coil you are using, internal or external resistor and if HP, you follow the manufacturer's instructions. It may take a while to damage a coil.

Think again about the distributor you are using. It is setup for a low RPM HT engine. It may not have correct timing curve if used on a higher RPM car or light truck engine. Improper/inadequate advance leads to over heating.

Be careful of the dist cap you decide to use. Aftermarket may be junk. You didn't have an earlier LOAD-O-MATIC cap on there did you?

I see what you’re saying about the distributor and advance curve. I didn’t have an overheating problem until the day it ran really rough. I think so far the advance curve is ok, we don’t get the truck much over 35mph and I keep the revs low. It’s an old truck and we’re unsure of the previous maintenance so I baby it.

I put a Napa cap on it this time, for a 1960 truck. I had used a cap for a 1957 car before I knew what distributor I had. I think it was just a hair too short inside.


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[Daves55Sedan]

Wouldn't an easy way to determine which cylinder is mis-firing be to take an inductive timing light and clamp the sensor around each spark plug wire one-by-one while engine is running. If lamp does not flash on one cylinder, there's your misfire sure as heck. I'm not sure if you can detect misfiring due to low intake vacuum, but it will sure run lousy with low vacuum. Your intake vacuum on a Y-block should be about 20 inches of mercury.

[runmikeyrun]

Originally Posted by Daves55Sedan

Wouldn't an easy way to determine which cylinder is mis-firing be to take an inductive timing light and clamp the sensor around each spark plug wire one-by-one while engine is running. If lamp does not flash on one cylinder, there's your misfire sure as heck. I'm not sure if you can detect misfiring due to low intake vacuum, but it will sure run lousy with low vacuum. Your intake vacuum on a Y-block should be about 20 inches of mercury.

Thanks for the heads up on the timing light. I was planning on doing that. The problem is most of the time I don’t have a helper to start the truck and sit in the seat while I mess around under the hood. I will definitely do that if my vacuum findings are inconclusive. Thanks for giving me the spec, I was going to have to look that up lol.


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[Daves55Sedan]

Originally Posted by runmikeyrun

The problem is most of the time I don’t have a helper to start the truck and sit in the seat while I mess around under the hood.

You don't need a second person to do that as long as the engine will idle by itself. An inductive timing light has a spring loaded clamp that easily fits around the spark plug cable near the spark plug. You just squeeze the clamp to insert it around the cable, then push the trigger on the timing light to see if the lamp is flashing. Then, squeeze the clamp to release it from the cable and move to the next spark plug.
You can check all the cylinders on a Y-block in just a few minutes this way. I have done it before many times (by myself).

[Milt K from Pa]

Mike,
A friend recently went through the same situation on a '40 Ford Pertronix conversion. Same brass filings in the distributor, rough idle poor running. He thought it was an incorrect coil and replaced it. Nothing helped so he went back to the factory points, ran fine. So he converted it to use standard points feeding an MSD box and all is well. If you get tired of fiddling with the Pertronix, try the old points.

Milt K from Pa

[KULTULZ]

Originally Posted by Milt K from Pa

Mike,


A friend recently went through the same situation on a '40 Ford Pertronix conversion. Same brass filings in the distributor, rough idle poor running. He thought it was an incorrect coil and replaced it. Nothing helped so he went back to the factory points, ran fine. So he converted it to use standard points feeding an MSD box and all is well. If you get tired of fiddling with the Pertronix, try the old points.

Milt K from Pa

... hmmph ...

THANX! for that info. I have read where PERTRONIX has been having quality issues of late.