Backfire causes?

Digger

Digger

Well-known member
Got the stock 39 to run. Let or run for about 20 minutes, it could turn off and then start again no problem. Then while revving up the motor, got a huge backfire, and now it won't start again. What would cause it and any solution suggestions?
 
If you had a 94 carb on it, you have blown the power valve. Its probably flooding now. Don't rule out ignition also. Check for spark, if it's there, go on to replace the power valve.
 
Check and see if you have spark first, if you do, then you have lean condition cause by gas not getting to the carb like it should. Out of gas ,block fuel line, bad pump, needle and seat stuck.
 
Before this happened, I put in fresh points and condenser. The carb is a Stromberg EBU that was just rebuilt by Mike Hubbard. So now will go back and do whatever need it over again.
 
Its a posable a bad connection to points or condensers or bad condenser .
Digger said:
Before this happened, I put in fresh points and condenser. The carb is a Stromberg EBU that was just rebuilt by Mike Hubbard. So now will go back and do whatever need it over again.
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There is no such carb as a strom EBU. you must mean a ford-holley ebu from a 53-54 ford.Like someone said you most likely blew the power valve. I would replace with a #5.5 one,you would also need a few gaskets. OMO ken ct. This is also not the carb to use on a 59AB engine.This is a loadamatic carb.Has vacume provision on the rear of it.No need for it. Use a #59 carb. Could be a vacume problem or timeing problem.
 
Digger said:
On the ignition side, what could have gonevout? Like the points frying?
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I've seen the same problem, when the ignition connection at the switch was not good. Intermittent ignition will cause huge muffler explosions, sometimes misinterpreted as backfires.
 
Another thing I don't see mentioned.... Do a close inspection of the distributor cap. Look for carbon tracks between terminals. On my own car (crab distributor), I recently had a similar situation - substantial 'firings' in the exhaust. What I found was a carbon track between #6 & 8. A new cap fixed it.
 
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