Technical The fantastic mystery of the great engine gremlin(318 Magnum "misfire")

I ran the ground wire to the distributor to make sure it had a proper ground and wasn't grounding out only through the intermediate shaft or anything. 318 distributors have o-rings instead of gaskets, and there's a thick coat of paint on the engine. But it seems it's getting adequate ground afterall.

When I ran a direct hot wire from BATT + to the distributor, it was with the HEI chevy style 1 wire installed.

As for the plugs, I'll clean em up. They're brand new with the motor, so I don't see how they could be bad beyond just being 'fouled'. Like I said, they're not oily nor particularly sooty, just black-ish and all uniform to one another.

I'll do just that. I forgot about that trick.

There's no symptoms I can think of that would manifest in both an HEI electronic dist as well as a points dist in the same exact way, unless I'm the most uniquely unluckiest guy in the universe(a distinct possibility).

It is indeed. Checked with a multimeter when the HEI was in. There's only one tenth of a volt difference between the battery and the ignition positive lead. All the other wiring for the points dist is brand new.

I'm going to order a different style coil tonight. One with a ballast built in. This seemingly ignition related problem is running out of ignition related causes really fast. I'll update when I get the new points, condenser, and coil in, though I have my doubts I'd like to have the spares anyway.

 

I'll test that tomorrow. Thank god my vacuum gauge is dual purpose.

 

You have a bisexual vacuum gauge?

 

OK, I'll go the other way from everybody else...could it be a fuel problem? Contaminated with water/condensation, just plain old/bad or junk floating around in the tank that gets picked up sometime? Be sure to let us know what fixes the problem.

 

Worn valve guide or egr valve unseating and then seating ?

 

Is your aftermarket cam the same firing order?….is your intake manifold single plane or dual plane??….if you don’t have access to an igniter “scope” hook up a timing light , stick it under th windshield wiper and take a ride…watch the flash pattern…make sure your exhaust pipes are open….no mice nest or any blockage….some exhaust pipe is double wall and the inside pipe can collapse causing a serious blockage….

 

Wow.

I replaced the coil with a brand new one, cleaned up the points while I was under there, and the old symptoms went away. Engine runs smoothly below 2,500RPM. New problem: it breaks up at anything beyond 2,500RPM and feels like I have a 2step rev limiter installed at 3,000 RPM.

So out of 4 coils I tried, one relatively new HEI accel coil(less than 500 miles on it! It came from the LA block), one HEI master pro coil(brand new in box, bought last year and sat on my shelf as a backup), one accel super stock coil(used), and one standard motor products coil(brand new in box), ALL OF THEM WERE BAD. Three being bad in the same way, and the brand new one being bad in a different way. I DID triple/quadruple check the ignition wiring.

So I suppose I'm on a quest to find a decent ignition coil now.

Thanks to all who've helped. Either I'm the unluckiest guy in the universe, or they really don't make them like they used too. Sheesh.

 

Bang on the money, only it happened to me 4 times in a row.

 

That is weird!! I have owned 25+ cars in my time and had exactly ZERO [0] bad coils. On the other hand, there have been numerous rotors, caps, wires, etc. go bad.
Good luck

Ben

 

I got a voltage regulator from AZ once... Eckler brand... for a Mopar. It wouldn't charge. I took it back and they tested it... No good. He pulled another one off the shelf and tested it... No good. None of the 5 others he had worked either. I ended up buying a Borg Warner and it tested good and fixed the car. Some times you do have to spend a little more for better quality.

 

Under the coil cover on an hei distributor is a ground strap.. make sure it’s there.. every bad coil on an hei I have seen was missing that strap.

 

I dunno ... I ain't convinced

 

OK, I might have been a little hasty on the new coil. I replaced the points and condenser inside the distributor and the motor runs all the way to 5 grand now. Oops.

I have had two HEI coils on two Chevys go bad on me. Specifically their power wires melting. One during a very long highway trip, the other seemingly randomly after about 10 minutes on the highway in a separate vehicle. It's why I switched to accel coils. I figured it was just the cheap coils.... Ive always liked HEI dists because of their wiring simplicity, but I think I'm just going to convert to points. From here on.

I do make sure they've got that strap.

 

It started out as HEI, I swapped over to a brand new points distributor after failing to pin point the issue.

I know I write long ass novels for posts so I don't expect everyone to read through it all. I just can't help it.

 

Thanks for getting back and posting what fixed it.

 

One of the wires on my ‘78 Camaro did the same thing, melted through and was shorting out. This was in ‘81/‘82. Only HEI I ever had that had an issue