I have a 1973 F-Body T/A with the 455 with the aftermarket Edelbrock that looks just like the original Q-Jet. My problem is the car is backfiring through the carb. and popping through the exhaust, and when you start it gas spits out the carb. I tried setting the carb. jets and idle screws and when I went to set the timimh I pulled the vacuun advance hose to plug it the car stalled? Do I possibly have a vacuum leak or what??? Thanks to anyone that can help! Steve

Turn the idle up, unplug the vac from the dist. , plug the vac line , and check your timing!!! Thats were I would start
And check to see if theres alot of play in the timing chain, via the rotor button in the dist.