Backfire
 

everytime i puch the as on my truck after i let go of the gas it backfires extremely loud (even more when i puch it). its a gen 5 454 with an eddie mani and 750 carb. could this be because im running too rich? or my timing is off?

Re: Backfire
 

probably a combination of the two, but i would start with the timing.

Re: Backfire
 

well i cant tune the dam carb thats the thng. its an edelbrock carb. i have to swich out jets and things. but i do not think im overcarbureting it. its not that big of a carb

Re: Backfire
 

not sure why you wouldn't be able to tune an edelbrock carb...

in the front at the bottom of the carb are two screws, they adjust the idle mixture. doesn't get any easier than that.
also check the operation of your secondaries. if they are sticking open, that could cause your problem, as the mixture will be too rich for the decelerating engine.

Re: Backfire
 

well i tried tem in 3 sttings. rich normal and lean. it still backfires. meaning its not the idle thats messed up. its something else.

Re: Backfire
 

am I reading this right? you snap the throttle, let off then snap again. on the last snap it back fires. I get the impression it is backfiring through the carb, ie. burnt/leaking intake valves. if it is coming out the exhaust I would look at the ignition system. (points, dwell, weak coil etc.)

Re: Backfire
 

intake gasket leaking or header leak will cause backfire on deceleration but on accel, is it backfiring through intake or exhaust? Valve or cam problems will backfire through card on accel. First check timing.

Re: Backfire
 

sorry for not being clear where is was backfiring from. its doing it through the exhaust. i checked for leaks and i got no leaks, it almost sounds like its burning up gasoline that's is left unburned on the exhaust system

Re: Backfire
 

next question. is the unburned gas due to fuel delivery or ignition problems? bump the timing up by 4 degrees and retest. let me know if that changes anything.

Re: Backfire
 

ok it did go away quite a bit, but now its hard to start due to precombustion. im afraid im gonna mess up my flexplate or starter. im at 16 degrees now in ignition

Re: Backfire
 

Backfiring out the exhaust is usually and ignition problem, check timing dwell ect.

Re: Backfire
 

UPDATE. it was an ignition problem. my timing gun was broken andreading ahead in advance. it was like 10 degrees in advance, so when i thought i was setting it to 12 degrees i was actualy putting it to 22 degrees in advance. i tried it with another timing gun. that would explain the hash start with what i thought believed "16 degrees" lol