I is a SBC 350 w/ the the 4-bolt main. The last owner upgraded the distributor to an HEI system. I have a feeling it might be the Distributor Cap, I just did sprak plugs about 2k miles ago and it has aftermarket Accel brand wires, The misfire occures always under load at ANY RPM, Putsing around or going flat out. Ideas, tips, suggestions?!?
Sounds like the ignition solid state module chip is faulty or a cracked distributor cap or it's burnt inside the cap.Also check the wires that feed that module bec they can fray and been faulty too.Be sure to check the ground going to the ignition module , plus those modules if bad can have a hole even blown through them or a bubble starting to appear where the internal short is inside itself.
Hope that helps and best of luck. By the way I'd probably go to a do it yourself big auto wreckers and select the best possible used replacement parts and take the whole assembly too.
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