Gas spitting/backfiring through carb

[JohnD]

Hi,

After installing my rebuilt transmission I have been having problems getting the car to idle and run smoothly. The car is backfiring and spitting through the carb. I have been reading/researching that this is usually related to the carb running lean. I have tried to reset the airfuel mixture and the car appears to be running fine and shortly afterwards the car start to die and spit/backfire again. So at the suggestion of my buddy Danny at Fun Imported I swapped the carb (from a DMSA to a DHSA) and the same behavior. The DMSA is going back on once I figure this out. A few other things to note (I think), I do have a mechancial fuel pump and I have read that it could be part of the problem. Also I have an old Crane Fireball ignition so no points on the car. Any suggestions would be appreciated.

Thanks,


John D. Nicosia

[seabeelt]

John, a couple of things to consider, test. Fuel pump. Mechanicals work fine, but if you are concerned, get an in line fuel pressure gauge and test the pressure. 3.5psi is the target. Plus or minus. Second, when was the last time either carb was rebuilt and properly adjusted?
R/

[carl]

Actual backfiring through the carb suggests an ignition timing issue. Also make sure your cams are set correctly.

carl

[JohnD]

Still trying to fix it. Put in an inline fuel pump and still spitting. Again the funny thing is that before tyranny change it was running great. When I use the timing light it appears to be flashing on the middle mark. Not sure how to proceed but really would to solve this myself. Any thoughts would be appreciated.

[azruss]

check to make sure you have your TDC timing set to #4 and not #1

[RoyBatty]

Did you open any fuel lines during the R&D process of the transmission?
The symptoms you describe do sound like a lean condition. Check everything to do with fuel supply. Pump output, filters and condition of lines. Also did you have any vacuum lines get disconnected accidentally?
Open the carb and clean all the jets and any sediment from the float chamber.
Good luck.

[vandor]

> backfiring through the carb suggests an ignition timing issue. Also make sure your cams are set correctly.

In my experience it is most often caused by a lean mixture. A lean mixture is often caused by a vacuum leak.