i just put a brand new barry grANt speed demon jr. on my 351w. i have the timing set at 12 degrees and it keeps on backfiring. the floats are set at about half way in the window and im not sure why it backfires? any help,do i have something set wrong?thanks for any hepl

 

Is it backfiring thru the carb or exhaust? Was the intake changed? Backfire under load or? Some more info and we'll see if we can help.

 

it backfires through exhaust, its a brand new engine so its got a new intake(performer RPM) and it only backfires at idle

 

the timing is at 8 defrees now, i lowered the foats and screwed i the mixture screws but it still has a light backfire???

 

Idle mixture too lean?

 

it might be ........im not sure how to tell