# Carb backfire



## CTCarGuy (Nov 17, 2009)

My 71 GTO 400 had starting problems after sitting a few days. I replaced the QJet with an Edelbrock 1400 (600cfm). The engine was sluggish before and now starts easily and has more pep. The problem i that I feel surging when I am in overdrive with the converter lock and now, without changing throttle position, the engine will backfire through the carb every so often. It happens under normal cruising. The wires, plugs, cap and rotor are new and the ignition is a Pertronix. The car starts easy and idles fairly well. I am starting to feel the engine getting sluggish again. I opened up the idle mix an additional 1/4 turn but all that did was lower my idle speed. Could adjusting the power valve help? It accelerates pretty well now but takes a lot of throttle. 

This seems like a lean fuel situation. I did a few full throttle quick runs and twice the engine flooded after releasing the throttle. Timing is set at 30 degrees at 2000 rpm. I did notice at idle that the timing mark jumped a lot but seemed OK at higher speeds. 

Ideas? I plan to do a compression and blow by test this week just to be sure it is not internal like a bad timing chain. I have no idea how many miles re on the engine but the car has 101000 and used a quart on a 4000 mile trip..


----------

