This is killing me! I have a 355 that I just CAN NOT floor without fireball-out-the-carb backfires.

I've tried 2 distributors, 2 coils, new plugs and wires (Plugs gapped). 5-6 different initial timings with a mix of no vac advance, ported, and full. Tried 3 different carburetors (600, 650, 750 double pumper) and I just can't get this shaken out. This is starting to absolutely drive me nuts.


The car runs great it idle (This is a 355 with Dart heads and a very mild cam) with about 8-12 degrees of initial timing, on full vacuum advance. Yea, I disconnected the vacuum advance when setting initial

As soon as I peg the car though, with an exception of doing so at a very high RPM, the car will backfire out the carburetor, and shut down. If I lean into the throttle, and avoid pegging it, it works out, and picks up very well.

I thought maybe I was running lean, but with a 750 mechanical secondaries double pumper? I'm out of ideas here.