chevy 350 backfire

[Twix27]

I just bought a 70 c10 and i've been trying to fix the backfiring problem. When i'm in drive it doesn't backfire but when i'm in low2 or low1 and i let off of the gas it backfires VERY bad sounds like a gunshot and its a bit embarrassing. Thanks for the help

[70rs]

I just bought a 70 c10 and i've been trying to fix the backfiring problem. When i'm in drive it doesn't backfire but when i'm in low2 or low1 and i let off of the gas it backfires VERY bad sounds like a gunshot and its a bit embarrassing. Thanks for the help

Is the backfire through the carb or exhaust?

[Twix27]

the exhaust

[70rs]

My guess is a timing issue. Without knowing what cam or other stuff you have I wouldn't know where to start as a baseline. Maybe one of the guys here whos better at that could chime in?

[Twix27]

its just a stock 350 with a 4 barrel holley stock heads, stock cam, everything is stock but headers

[MarkM66]

What do you have the timing set at?

[Twix27]

its at about 750 to 800

[70rs]

its at about 750 to 800

That is the idle RPM. Do you have a timing light?

[Twix27]

no i do not i can go rent one though what would you recommend the timing at

[MarkM66]

no i do not i can go rent one though what would you recommend the timing at

10* btdc would be a good start.