ok, ive been wondering this for a long time : why does every 305 motor in a 3rd gen have a missfire? Ive owned (3) 3rd gen T/As, and just recently purchased a 84 Z28, and all of them had a miss. Bad ones too. Besides cap/rotor/plugs/wires, what else could cause this to happen in this motor? Ive also owned (2) 350s (both tuned port), and neither of them had this problem. Just in case it matters, 2 of the 305s were TPIs, one was the Crossfire motor, and the Z28 has the LG4. Any help is appreciated.

 

Considering that the 305 and 350 are identical in practically every way except bore diameter, I'd say you are a victim of bad luck.

Besides tune-up parts, things that can cause a cylinder not to run are a blown head gasket, or damaged valve train parts (bent push rod, rolled cam lobe, bad rocker, etc.). These things can happen equally easily to a 305 or 350.

 

Besides the mechanical things RB listed, could be pickup coil, ignition module, reluctor..possibly the coil as well, bad injector.