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Saturday Night Racer >> RACE TECH >> Backfire thru carberator
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Message started by Hit n run on 04/11/10 at 6:54pm

Title: Backfire thru carberator
Post by Hit n run on 04/11/10 at 6:54pm

When i rev up my engine it started backfiring thru the carb. Checked the timing.plugs and wires,changed the power valve,everything looked OK inside the distributor. Any suggestions or similar experiances ?

Title: Re: Backfire thru carberator
Post by imracin68j on 04/11/10 at 7:24pm

cam timing?

Title: Re: Backfire thru carberator
Post by Hit n run on 04/11/10 at 7:29pm

The problem started after a few laps into hot laps.The car has not been used for the last year, but before that it ran great.

Title: Re: Backfire thru carberator
Post by OLD SCHOOL#6 on 04/11/10 at 7:40pm

Possible sticky or bent intake valve, possible weak or broken intake valve spring ...................

Title: Re: Backfire thru carberator
Post by Hit n run on 04/11/10 at 7:48pm

The engine runs a little ruff at idle and has a misfiring cylinder.Also you can hear a poping echo sound every few seconds thru the exhaust.

Title: Re: Backfire thru carberator
Post by Andrew on 04/11/10 at 7:51pm

Do a compression test, I'l bet you find which cyl is weak, then check the valve springs before you tear it down.

Title: Re: Backfire thru carberator
Post by Hit n run on 04/11/10 at 8:06pm

I have considered changing the carb and or distributor.

Title: Re: Backfire thru carberator
Post by miniguru27 on 04/12/10 at 10:27am

I would try checking the valves the springs.and the cam to make sure there is not a flat lobe.Just an idea.

Title: Re: Backfire thru carberator
Post by brummi5050 on 04/12/10 at 11:26am

Rev it up a little to where its popping back through the carb and pull 1 plug wire at a time till the noise goes away. Exaust lobe or valve bent.

Title: Re: Backfire thru carberator
Post by Hit n run on 04/12/10 at 8:23pm

Thanks for all the suggestions,I decided before looking at the worst case stuff first to look at the simple stuff one more time.When i looked at the firing order i found #6 and #8 were in the wrong order.Hopefully the misfiring did not cause any damage to any other parts. Thanks again for the suggestions.

Title: Re: Backfire thru carberator
Post by Andrew on 04/12/10 at 8:32pm

K- keep
I- it
S- simple
S- stupid

Good find! I'm embarrassed that I didn't think of that. ALWAYS go through the simple stuff first.

Title: Re: Backfire thru carberator
Post by imracin68j on 04/14/10 at 6:23pm

I think I would have pulled the motor down, swapped the cam, bought a new carb and THEN checked the spark plug wires.. but hey, that's just me.

Title: Re: Backfire thru carberator
Post by Hit n run on 04/14/10 at 9:51pm

It took a phone call to Dad who said to look at the wires and plugs again. I guess the man upstairs has his way to get us to call our parents when we have not been calling them enough.

Title: Re: Backfire thru carberator
Post by Watchin15B on 04/16/10 at 2:32am

imracin68j wrote on 04/14/10 at 6:23pm:

I think I would have pulled the motor down, swapped the cam, bought a new carb and THEN checked the spark plug wires.. but hey, that's just me.

I don't think thats just you Billy, I think quite a few of us may have done that!! Good job on finding the problem out without tearing stuff up!! I guess some of our parents are smarter then we think lol!!

Title: Re: Backfire thru carberator
Post by Andrew on 04/16/10 at 11:03pm

My dad is my "phone a friend" when I can't figure something out too. Wish he didn't live so far away. I miss the old guy.

Title: Re: Backfire thru carberator
Post by 56HS on 04/17/10 at 6:54am

I think i'll give dad a call today before we go out to the track.After all the stuff he put up with over the years, everyday should be Fathers day.