Classic/Antique Car Repair: 1964 Chevy belair 230

Question
My car recently started back firing through the carburetor while under a load.ive tried adjusting the distributer with no luck. I'm about at my wits end any help would greatly be appreciated.

Answer
I would assume that this happens on acceleration or when the engine is under load. There are three areas that I would first check. First I would check the distributor cap to make sure there are no cracks that run from one spark plug terminal to another. The second would to be sure that the accelerator pump in the carburetor is working. To do this with the engine off remove the air cleaner. Using a flash light look down into the throat of the carburetor and quickly open the throttle. You should see a stream of gas if the engine is a six cylinder and two stream of gas with an eight squirt out. If the accelerator pump is not working when you step on the gas the engine will go lean and backfire and bog. If the accelerator pump is working and the cap is not cracked I would check the compression on the engine. A burned intake valve will cause the engine to backfire up through the carburetor. A burned valve will give more than one pop back up through the carb, as it will pop each tie that cylinder fires.