VampireHunterC

I have posted before about my carb troubles. Specifically, I posted that my secondaries were not working. Well, I was not completely correct. I hit WOT on the way to my mom's house this afternoon. I can tell that gas is being dumped into the secondaries at WOT. The sound of the engine gets louder and rougher, but the car slows down, and you can smell the gas. When I got to my mom's house, I popped the hood and pulled the carb to WOT via the throttle linkage. The AV flaps opened VERY slowly, and fire shot out of the carb! So, any ideas? I looked at the tech article "tuning your cc Quadrajet for performance" or whatever it is called, but I did not see a screw under the lip of the AV assembly to loosen prior to adjusting the linkage. Of course, the a/c condensor was kinda in the way, and it was getting dark.

RB83L69

Fire shooting out the top of the carb = backfire, usually from being too lean.

Sounds to me like at least one side of the secondaries may not be feeding fuel. Although, if the air valve will open under no load, it's probably improperly adjusted. It almost never opens by revving the engine under no load, it should only open when the engine is demanding lots of air flow, which only happens when there's a load. Odds are, if it opens at all that way, the AV spring tension is set too loose. People seem to think somehow that if the valve slams open it will somehow eliminate the bog so they loosen it up too much. I guess they must think that the slow opening of the valve is what creates the bog, but that's not true. When it's too loose, it makes the engine suck in way too much air for the amount of fuel being fed; the engine goes drasticaly lean; and you get the famous "bog", backfiring, etc.

The AV adjustment screw is on the underside of the air horn casting, on the pass side of the carb, immediately underneath where the AV shaft passes through the casting. The actual adjustment is a small slot screw in line with the end of the AV shaft. Loosen the set screw with an Allen wrench, it's about a 5/64" IIRC, and the adjustment willl sring itself to zero tension; turn the adjustment about 5/8 of a turn clockwise from there, and re-tighten the lock screw. Drive the car and see if it's any better.