I have a 1986 IROC Z28 - 305 4bbl, 5 speed manual and 373 limited slip rear. When I first got the car, it would not run and had to fix the timing on it. The car runs ok, but when I floor it at low RPMS, it tends to bog down. Seems that the carb is working ok, once, I get some RPMS in it, I can floor the gas pedal with no issues. The Distributor has been suspect since I got the car. Can I replace the ditributor with a non ECM controlled vacumm advance with out replacing the intake and CARB. That will be my next purchase besides exhaust. I am trying to keep the mods to a minimun since I am working on getting a 350 and completely redoing it( or just get a 350 crate). Not sure which way I wanna go yet. I do not need to worry about emissions so that not my concern. I tagged it as a classic and strickly keeping it for a weekend hot rodder type play toy.
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An HEI should work fine. You can get one from Jegs for like $90-130.

 

Have you checked the lash in the carb linkage? Make sure the throttle valves are opening at the right time. I had a carb engine doing that years ago and it was the set up in the linkage between the primary and secondary...