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Poor ignition 86 chevy 74 350 motor

My truck is a 86 chevy dually with a 74 350 and a 4bbl carb.

I just changed my plugs, wires, cap, and rotor. It ran fine and sounded good after I changed everything, and then when I was driving down the road it just lost power and started missing really bad. It still starts and drives. I checked to make sure my connections on all my wire towers were tight and they were. I took off my cap, and made sure my connections were tight.

I don’t really know where the problem is. It is NOT a case of a wire being on the wrong tower. I numbered all of them and did them one at a time, and it was running fine right after I changed everything.

Have you determined if a specific cylinder is missing?
Have you performed a compression check?
I would also recommend connecting a vacuum gauge while it’s idling.
Perhaps something got loosened/disconnected during the tuneup?

I made sure everything was still tight so I dont know what would’ve got loose. I don’t have a vacuum gauge so I need something I can try with my hands.

tried to make video

In the cap, under the coil, a flat piece of metal bent in a “dog leg” shape was under the coil.

Did you transfer that piece from the old cap to the new one?

I didnt see that part.

Does this engine still have the contact point distributor or has it been swapped over to HEI?

Did you put points in and if so did you clean the oil off the points first?

It is a HEI

If your distributor has the coil mounted in the distributor cap that ground strip needs to be installed.

I have the ground wire and the the positive and negative connected. The ground is internal.

With cap and rotor off, under a good light, gently pull on the wires that go into the ignition module. Look carefully where the wires go into the plastic module. They should not stretch back at all…if they do, the fine copper wire inside the insulation may be broken, separated, from the constant motion as the vacuum advance moves the breaker plate back and forth…

These ignitions had a reputation of being simple and trouble-free…


those two wires in the first pic attach to the coil on top. I know the distrib is rusty but maybe the ECM?

Also it sounds like it’s reving to much and no carb screw adjustment hardly effects it.

“caddyman” I’ll try that in the morning it’s getting kind of dark here. I hope it’s not the ECM. They are expensive…


That’s too much rust…That top plate that mounts the rotor is the centrifugal advance mechanism…It must be free to move (rotate) on the distributor shaft and return smoothly pulled in by the little springs on the advance weights…If you look down in the housing, you will see the kidney-shaped module. It might be time to remove the entire distributor from the block for a complete and through cleaning and inspection…Before you remove it, mark where the rotor contact is pointed and put it back in the same way…DO NOT turn the engine over with the distributor removed…Back in the day, they sold rebuilt distributors that were ready to go, all the worn parts replaced and everything setup and adjusted…

Do you think I can get away with pulling it and cleaning with a rust removing gel? Also why would it start acting up after I put all those new parts on?

That engine has no ECM.