Engine backfires after warming up

[lewglo]

Have 318 Chrysler engine - runs great until it gets warmed up and then on low speed backfires. Have changed coil. Carburator has been adjusted. Electronic ignition has been overhauled. Any suggestions?

[g36]

i know you said the electronic igniton was overhauled but i wondered about the centrifical advance working properly, have you verified that part of the distributor?

[sluggo]

Have 318 Chrysler engine - runs great until it gets warmed up and then on low speed backfires. Have changed coil. Carburator has been adjusted. Electronic ignition has been overhauled. Any suggestions?

water in the gas someplace??

[larryeddington]

fuel going lean can also cause gassers to backfire, is it on acceleration or just when ideling or running smoothly.

[lewglo]

Under load but almost idling - coming back in to dock about 10 rpms

[Big D]

This symptom is sometimes the result of the ignition system not coming off advance after reducing throttle. Check that your advance mechanism is returning/springing back as g36 said when you throttle down. You can check with a timing light or open up the distributor and access the advance mechanism; move them by hand then let go and see if they return all the way on their own. Clean everything up and be careful not to damage the springs. If your unit's shaft can be oiled at the top when rotor is removed (will see little felt pad in top of shaft), oil it and rotate shaft back and forth a couple of hundred times; more fun with a beer in the other hand. Run it in the slip with a timing light to about 2k rpm then throttle back and see if timing returns to base. If base on your application is 5 degrees, it should be slightly above that if timed right.

[rooferdave]

if it only backfires AFTER warming up it sounds like a fuel issue, too lean can cause backfiring and the only thing that changes between a cold engine and a hot engine is the fuel mixture. Timing, spark and such remain the same (coil can breakdown I guess but causing a backfire?) With the choke on it will run rich but when it comes off if there is a fuel restriction it will cause the engine to lean out and backfire.

To test this theory of mine next time you start up pull the air filter/ spark arrester and have you or someone watch, when the choke opens see if this is what sets it off, and if it does put it back on to see if it solves it. If it does look at all your fuel filters, ccthen fuel pressure for you pump. Hope this helps.

now only if I can figure out my issues