i have a 350 ho gmpp crate motor with holley 600 an edelbrock 2116 intake, in tank pump with a mallory reg. and i have my timing set at 10 deg. adv. i am getting a backfire when i step on the gas occasionally, and sometimes setting still when playing with then gas pedal. any one have any ideas?

 

usually blowing through the carb is a timing issue, either not enough base timing or not enough vaccume and mechanical timing.

 

What specific Holley 600 do you have?