exhaust backfire?

[berg bronco]

heres the problem I installed a bran new holley 4v and a edelbrock perfomer intake runs good but i have major backfire out of the exhaust when i let up on the gas ive checked the timing new plugs new wires new vacum lines i thought it was runing rich so i adjusted the mixture screws in as fars as i could so it would still run (2 turns from tight if that makes sense) but still major backfire any advice?

[berg bronco]

oh ya I forgot the timing advance port on the new carb has no suction is that alright?

[firefighter2134]

if you have a vacuum guage hook it up to timing advance port on carb and set it to the guage. that should set your mixture right.

[berg bronco]

I dont have a vacuum gauge. are they expensive?

[firefighter2134]

25 bucks

[berg bronco]

should that help with the backfire?

[firefighter2134]

the vacuum guage will let you fine tune the mixture along with the timing. you can get it close with timing light. then use the guage to fine tune. is it taking all fuel when you burp the throttle or trying to stall out?

[berg bronco]

you can hit the throttle and it doesnt stall or stutter it seams to run good it just seams to be runing rich

[berg bronco]

i checked the timing and it was right on but a local guy told me to advance the timing a little that would help the backfire but I didnt notice any differance

[blazinchuck]

set the mixture...with pulling the most vaccum as possible..., reset idle after adjusting,then check timing again.