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Author Topic:   Backfiring
demonseed
Dirt Newbie

Total posts: 4
posted August 30, 2005 10:02 PM  

I run a street stock on a 1/2 mi asphalt 355/2bbl/7448/350 holley w/68 jets/390/410 racing cam.. dur-??? HEI dist. with the weights welded.38* timing.. anyway last week i changed my heads to 441(had junk 883's on) w/ 313 intake.took it out sat and noticed a backfire everytime i let off the gas before entering the turn.it didn't do that with the other heads. i replaced the power valve in the carb and reset the float and retimed but still backfires... is this hurting anything??? am i dumping to much fuel??? the car is alot faster but i just don't want to break anything. any advice is greatly appreciated..thanx

sc1 racing
Dirt Freak

Total posts: 419
posted August 31, 2005 04:30 AM  
people will tell you your engine is running to rich, but if you want to fix the prob try a set of 76 jets and reset carb.

leapinlizard
Dirt Freak

Total posts: 402
posted August 31, 2005 07:26 AM  
Backfire thru the exhaust or thru the carb?

Thru the carb: I'd say you have a valve missadjusted or a leaking intake or other lean condition ahead of the cylinder heads.

Thru the exhaust is a common problem with leaking exhaust gasket's and misadjusted idle screws. You may have to much transfer slot showing.

ss99
Dirt Maniac

Total posts: 120
posted August 31, 2005 07:36 AM  
What leapin' lizard is asking is important. Having swappped heads, I'm sure you had to at least partially disconnect your exhaust. If you have a small exhaust leak in the area of the header primaries or collectors, it's common to get a pop or series of pops as you let off the gas. It's the unburnt fuel mixing with the fresh air igniting. So, it the popping is coming from your exhaust, look for that exhaust leak.

demonseed
Dirt Newbie

Total posts: 4
posted August 31, 2005 08:49 PM  
I forgot to mention the backfiring is coming out the exhaust pipes. i didn't notice any leaks. i have stock exhaust manifolds and put all new (felpro) gaskets on. LEAPIN LIZARDS... what do you mean by having to much transfer slot showing??? like i said all i have is stock exhaust manifols with a 45* and 90 bends off of them going straight back to beind the doors.2 1/2" pipes... thanx for all the replies..

demonseed
Dirt Newbie

Total posts: 4
posted August 31, 2005 09:13 PM  
I forgot to mention the backfiring is coming out the exhaust pipes. i didn't notice any leaks i have stock exhaust manifolds and put all new (felpro) gaskets on. LEAPIN LIZARDS.. what do yo mean by having to much transfer slot showing??? like i said all i have is stock exhaust manifolds with a 45* and 90* bends off of them going straight back behind the doors. 2 1/2" pipes.. thanx for all the replies.

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