carb backfire

[jerdan]

I am having trouble getting my 1953 ford flathead v/8 to idle and accelerate smoothly. It idles rough and when I pull the choke out a little it smooths out. I am running a holley 94 2 barrel. It backfires back thru the carb when I stomp on it. I am running electronic ignition with stock dizzy. Any suggestions would be greatly appreciated.

 

[petehoovie]

Usually, a backfire will cause damage to the power valve in a 94 carb....You'll get leakage....

 

[fordscript]

Sounds like its running lean....maybe a vacuum leak somewhere?

 

[Flathead Fever]

Sounds like its running lean....maybe a vacuum leak somewhere?

That's my guess too. A lean condition will cause a backfire out the carb.. Maybe a low float level. Accelerator pump not squirting. A large vacuum leak.

Try some propane around the base of the carb and see if it smooths out. You can use starting fluid too. Make sure the carb mounting bolts are not loose.

 

[Init1]

Backfiring through the carb can mean retarded timing.
Check it out.

 

[rotorwrench]

Pulling the choke makes the mixture more rich so if it runs better with the choke partially on then it's not getting enough fuel through normal channels. If it's only at idle then the idle circuit could have obstruction. If it' bad all the time then the main metering could be obstructed. If it's only during acceleration then it could be either the accelerator pump or the power valve being obstructed. An engine starving for fuel will pop back through the carb so that's another indicator of a lean condition. Fuel pump output or float valve can also be suspect of problems on this symptom.