Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

no control over AFR's

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Marx3:
Hi, I recently rebuild a 17059253. The carb stayed completely stock except for a little modifications to the idle system
mixture holes: .090
by-pass: .98
DCR: .052
I did not pull the tubes to up their size ( maybe a mistake ).
It idles pretty strong actually, but makes zero vacuum ofcourse.

The carb was put on a smog 7.5:1 mopar 400 engine with a horribly mismatched cam
dur. 274/286 lift .488/.491 on 110/106 ( someone gave bad advise )
Engine starts good, idles good, pulls good, response is good. everything seems good given the circumstances ( ;)) BUT
with stock jetting and airbleedsizes it read about 18:1 at cruise and 11:1 at wot.

I took the 73 jets and the 50 ( or thereabout) rods out and put in 74 jets and 43 rods. now it showed 13:1 at cruise and about 14:1 ending at 11:1 at wot. I put in 44 rods and turned the APT down to about 1.5 turns. now it showed 16.5: at cruise and at wot it started out around 14:1 and ended up around 12:1. I backed out the APT to about 3 turns, now it showed 15.5:1 at cruise and although starting out too lean it ended up at 12.5:1 at wot.

I cant understand why I have so little control over the AFR?

I can add that I remember now that I did not change the powerpiston spring to a lighter one... ???
 

 

Cliff Ruggles:
Which 44 metering rod did you use, "K" series, "L" or "P"?....Cliff

Marx3:
K...

Cliff Ruggles:
K rods only offer .005" taper on the upper section.  If you desire more control use a full tapered rod, or P series rod, which has .010" taper.

All of those rods have .026" tips, so you should see no change at WOT between any of them.........Cliff

Marx3:
Okay, note to self: use tapered rods!

Thats the weird part... changing primary rods seemed to have a substantial effect on AFR at WOT

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