Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

A few issues

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Cliff Ruggles:
Lean "tip-in" is not power piston spring related, as the vacuum is really high at light load.  Raise the APT and see if it helps.  If you end up more than 5 turns up from seated, try going to .077" main jets.

Did you verify the position of the metering rods in the jets during the rebuild?  We end up bending the primary hanger arms in at least 90 percent of the carbs built here to get the metering rods correctly located in the jets......Cliff

jxu109:
OK, will try the APT --

Where do I find info on positioning rods?

Thanks

Cliff Ruggles:
The positioning of the metering rods is done by leaving the float out and installing them.  Never assume the hanger is exactly the right height, verify by looking at the metering rod location in the jets in the up and down positions. 

It's pretty common for hangers to be bent from prying them out of the carburetor.  The arm also comes up in the piston and may need re-seated.  When correctly set, the tips should be in the smallest portion of the jet, up high enough as to not obstruct the entrance.  In the down position the fattest portion of the metering rods should be in the smallest portion of the jets, but not so low as the fattest portion of the rod is obstructing the entrance to the jets.

APT carburetors allow us to custom postion the upper sections in the jets externally, which is a really nice feature......Cliff

jxu109:
Good to know.  I'll check it out.  Turning out the APT seems to have tamed the surge, but not eliminated it.  I think I'll just have to call it good where it is, and if it's still pinging, I'll try to take away some initial timing.

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