I have an '84 Z28 that will backfire (in the carbuerator) upon deceleration. However, when I drive to work (or Home) and turn off the car; BOOM!!!!!!!! It sounds like a shotgun. This backfire is in the rear. The carb backfires are most likely due to the carb needing a good rebuild. The backfire from the rear is so loud, that I am worried about serious damage if it is not addressed. I am planning on replacing the ENTIRE EXHAUST SYSTEM, but could it be something else?
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I've had it do that through the carb (often called a "sneeze"), and increasing my spark advance fixed it. It was more when Id stomp on the gas though, not on decel so that may be different. Timings a good place to start checking anyway. If you still have the quadrajet, they work better with the advance set to about 6before (with the control wire unplugged) rather than the 0 as suggested on the sticker.