Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

Idling engine dies below 950 rpm

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Cliff Ruggles:
Get that junk out of your distributor and put the stock parts back in it. 

Hopefully that will improve things some....

dkraven:
I appreciate your response and understand in your experience a lot of the stuff out there is cheap junk, but I also want to understand why. This stuff doesn’t come easy to me, but it’s interesting.

The distributor tune up kit came with a new module, vacuum advance, weights, and springs in addition to the rotor and cap that I actually needed to replace. I do still have the old va, module, weights, and springs, though the old weights and springs were starting to rust a good deal. But why would those parts affect the base idle?

quadrajam:
The weights and springs will sling outward when you rev up the engine advancing the timing.
Then when you let off the gas the springs must pull it all back but if rusty and gunked up
this wont happen. It wont return to initial timing.  At least not consistently. Also the
upper shaft is lubricated by grease from the factory. It can get sticky as well. If so, you
will have to totally disassemble it to put grease where it needs to be on the shaft.
Might be a good idea to get a shaft shim kit and new roll pin too.

Like Cliff said clean up and lubricate the old stuff and if its not too worn out you can
get by with it. And If your original module is a GM it may be more reliable than what you bought.

QJ

Cliff Ruggles:
There are fundamental flaws in those aftermarket spring/weight kits.  They not only change the weights and center cam, they change the geometry between those parts.  The idea is to get the timing "all-in" much sooner.  What happens with every single one of those kits I've messed with is that they are certainly good and getting the timing in, and in quickly.  However, they don't have enough spring tension so pull the timing back to the base setting at idle speed.  By the time you put enough spring tension on them to keep some of the timing out at idle speed, the advance curve has a "delay" and doesn't come in early or smooth.

The factory knew what they were doing and the springs, weights and center cam will provide an ideal timing curve starting just above idle speed and advance smooth and steady with RPM increase.

The problem, as mentioned above is rust, dried up grease and wear on the parts.  Once completely/correctly rebuilt your factory HEI with the stock parts will work flawlessly.  I'd go that direction and ditch the aftermarket kit.........FWIW....

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