Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

Pinging at WOT second gear

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l.neidlinger:
Hello all,

I have a 1982 GMC C1500 that I have been slowly getting the carb dialed in after having to fix vacuum leak after vacuum leak and other problems the truck has had after sitting for 10 years.

I bought a rebuilt carburetor for it, but have been having problems with it pinging at WOT in 2nd gear, right around 65 MPH, about when you can hear the secondaries start to open. The balancer has, unfortunately, slipped and I cannot accurately set the timing. I run 89 octane gas, and have the base timing set to where it won't ping at WOT in 2nd anymore, but it seems that is set too retarded as it bogs and backfires up through the carb if you accelerate hard from a stop or low speed, and if you punch it at cruise, the engine stumbles for a second, then picks up. I checked the accelerator pump shot, and it seems ok.

I took the secondary rods/hanger out and found some interesting things the rebuilder did. The passenger side rod is a "CH" rod with a large witness mark ground into it, the driver side rod is a "DR" rod, the hanger is a K. Could there be some problem with the secondary rods being too lean, or the air door opening too late?

Here is a (admittedly blurry) picture of the "CH" hanger:

l.neidlinger:
I should have specified - Truck has a bone stock 305.

I still have the stock quadrajet that came on it. I took the secondary rods out of that to compare. It has a J hanger with DR rods. The rods look very good, I may pop those in with the J hanger and see how that works out.

l.neidlinger:
Threw in the DR rods and J hanger from the original carb and drove it to the store and back. The bog at WOT seems to be greatly reduced, but the weather has been colder today and this carb seems to love to run completely different if the temperature outside changes even just a little, so I will have to see when it decides to actually be spring around here.

I did notice, now, what sounds to me like "light" pinging at WOT at lower RPM's. I could just be crazy. A 305 couldn't be this thirsty.

Cliff Ruggles:
The best thing you could ever do here is to completely and correctly rebuild the original carburetor and put it back in service........Cliff

l.neidlinger:
Unfortunately someone tried replacing the mounting gasket on this truck some while ago and when they tightened the fitting for the brake booster too tight and cracked the throttle plate.

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