oxfordbp

Why would I be backfiring after i shut er down? Doesn't seem to be running lean (sniff test) and I think the timing is ok, I don't have a light yet.

Could it be because I am idling too high, no tach yet either...I raised the idle cause it would die when I put her in gear.

Oh and I have a vacuum leak under the carb that I cannot get rid of, if that helps at all!?

Stepman

Fix the vacuum leak and set the idle back down. That should take care of it.

oxfordbp

Thanks

musnicki

Also, check for a leak in the headers either from the heads or to your pipes. Not having enough back pressure can cause gas to drip down into the headers.

Running a bit rich can cause a back fire as well. When you shut the car off a few drops of gas can drip down into/onto the hot headers and ignite after the car is off.

It's definately not from bad timing, which would be another cause for a back fire.

James

JMD

You answered your own question!

A vac leak can get one or more combustion chambers too hot. When the fuel/air settles around a hot valve, or other hot spot in the chamber, the mixture is ignited, causing an explosion that can go up the intake, or down the exhaust.

If you have either aftermarket "big port" heads, and/or a "big port" intake, I have found that SBF intake gaskets can be a bitch to seal up, as they will "bolt in" in lots of positions that will not seal the ports, and the margins where the intake actually meets the head for sealing can be very, very, thin.

oxfordbp

Sweet, fixed the vac leak, running real nice now. Thanks everyone