429 Hesitation - too Lean or Too Rich?

I have a 429 with a holley 770 street avenger - when i step into it backfires and hesitates - is this because i'm starving the carb or dumping too much fuel?

Originally Posted by 69thunderbird

I have a 429 with a holley 770 street avenger - when i step into it backfires and hesitates - is this because i'm starving the carb or dumping too much fuel?

Sounds like you may have the timing off. Check the initial timing, and the vacuum advance, also look for a worn distributor cap, rotor, old or arching plug wires, before looking at the carb.

Almost certainly not rich, although in extreme cases it could blubber or foul plugs and then cause a backfire

I would first check to see if the accelerator pump works with even the slightest throttle movement with no bubbles or spits. If it isnt nice clear immediate streams, fix the accel pump

Next would be checking the firing order, then check for vacuum leaks

Last would be a leakdown test looking for a bad intake valve.

Yes, check the adjustment on the accelerator pump. It should give a good squirt when you move the throttle a little bit more then a tap.