I officially have a poltergeist living in my 304. I did the tr upgrade and now it backfires up the carb when i have it under load. 2 shops are stumped by it. One thinks it is in the distributor because it seemt to only do it with the vacum advance disconnected. The other thinks it is a weak mechanical fuel pump they think a carb should get 15+ psi but my edelbrock manual says 6 psi max. Oh, and the motorcraft ignition box was getting so hot it cooked one and split the epoxy in it!
If anyone has some fresh ideas please send them my way!!
81 CJ7 304/904/D300 scout 44's locked, full cage, 33"wildcats, warn HS9500i, bush bar from hell and diamondplate sides to cover gaping rust holes!! Coming soon OBA!!
And people wonder why I do my on work? GRRRR... I'm dumb but most mechanics I know are dumber and it's not a pretty sight when we get together. There are a few reasons for backfiring... and check 'em all out:
1. Timing too far ADVANCED.
2. Bad valves, burnt or bent.
3. Running to rich.
4. Decelleration valve bad, if you're emissions are intact.
5. Carbon build up in the cylinders or on the valves.
6. Heat range on the plugs too high.
7. Carbon trails on the distributor cap.
8. Bad Vacuum Advance on the distributor.
9. Dist rotor arcing to dist. shaft.