Breathing Backfire?

Question

i have aftermarket carb and headers. i have been told that pinholes in headers could cause problem. i have also learned that imcomplete combustion of fuel would cause that, thus leading me to timing... or a/f mistuned on carb. could both or neither..what else could cause this? HA! or only driving style?

84 chevy 305, edelbrock carb,3" headers, mufflers. no cat conv. no other pertinent alterations...other than emissions crap.

i do not backfire always..and there is no fire spewing from the carb itself.

Answer 1

Not the carb...it's a weber, they just don't have anything that could go wrong other than maybe the power valve needle is stuck open. Possible that the carb is too big for the motor. It does sound like possible overfueling. Check your timing. Do a compression check. If that all checks out you should try a smaller carb. Good luck.

Answer 2

Is the backfire occuring under a load? You did not mention the mileage on the engine, but a worn cam lobe can cause a backfire during acceleration, and a worn cam is common on the small block chevy's at high mileage. My 327 had similar symptoms when I wiped a lobe.