i got a small block 350 backfiring through the carb, i have 9-1 compression, a 490 lift cam, roller rockers, pro-racing heads, and an edelbrock performer RPM high rise intake manifold with a edelbrock 750 carb, MSD 6A ignition box with an MSD HEI ignition coil. the motor was just built from bare block 1500 miles ago. i changed the plugs, cap and rotor, and ignition coil...i need some possible causes...

Timing? Distribuitor 180 degrees off.

the car was running fine, i didnt touch anything until it started backfiring, thats when i did all the changes. the timing is 10 degrees

When does it backfire under acceleration or when you first hit the gas
if when you first hit the gas is it only when you mash it or when you ease into it too
what kind of carb?

Does it do it consistantly at a cruesing speed without giving it more or less gas?
Have any new ticking noises from lifters?

it only backfires right before its ready to shift gears...at idle, it backfires around 2500 rpm's only when you hit it, if you ease into it your fine...the lifters have always had a little noise because their roller rockers...

If you accelerate at a constant throttle position automatic tranny your saying it backfires while changing gears?

or is it a manual tranny and you let off between gears?

What kind of carb?

if its idling in neutral and you nail it all at once will it spit back through the carb and cut off? If so probrably trash in the accelerator pump discharge or bad accelerator pump diaphram. If as you say it was working fine.

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1972 Camaro 350 factory heads 1.94/1.5 street driven full interior everything works 7.59
89.54 mph

Pull the valve covers and eye ball check the rocker motion while spinning the motor over.If you have a bad lobe on the exhaust side it will pop out the carb.I know I'm not the only one thinking that.

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1978 Z-28 purchased new by me -$6750
Click here (http://f1.pg.photos.yahoo.com/ph/someonehasthisid/detail?.dir=/d752&.dnm=aefd.jpg) to view present state photo
Look above for glory days.
1994 Formula
1982 350 S-10

[This message has been edited by Mike-78 Z-28 (edited December 01, 2004).]

yeah thats what i meant when i said do does he have any new tcking noises from valvetrain! http://www.nastyz28.com/ubb/biggrin.gif

<font face="Arial,Verdana" size="2">Originally posted by Mike-78 Z-28:
Pull the valve covers and eye ball check the rocker motion while spinning the motor over.If you have a bad lobe on the exhaust side it will pop out the carb.I know I'm not the only one thinking that.

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Unfortunately, I have to agree with Mike. It sounds to me like you have a worn cam lobe there amigo. Check your valve lash.

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'Silver Bullet' 1977 Z-28 413" SB
11.73 @ 115.10 and dropping...
Old Vortec combo:
12.15 @ 110.52
1989 GTA L98
Daily driver