Quadrajet Problem Solving > Dialing in your rebuilt Quadrajet carburetor
Main air bleed screw 7040263
comp:
let us know
Cliff Ruggles:
Mark, looking at the combination, I'd go to .073 or even .074" main jets, and .041" primary metering rods. The aluminum heads, big cam, and the fact that modern fuel is lacking some in energy content, diluted with ethanol, etc usually requires more fuel clear across the engine rpm/load range. We have all the jet numbers, and .041" rods new and used in the shop. I'd also replace the power piston spring with a new one, we offer an assortment of them for custom tuning......thanks....Cliff
Grych:
Greetings, my last test session on Sunday I was already leaning (no pun here) towards your suggestions with larger jetting. Thanks Cliff. I used a 73/39 combination which provided slightly more fuel during part throttle and it provided mixed results.
Part throttle, which to me is 30 mph down main street the lm-2 was indicating 13.5 to 14.0 AFR. Hwy Speed, which was 55-60 mph the LM-2 was around 14.0-14.4 AFR. The car ran smoother as the surging was now gone.
However, upon decceleration from either hwy or part throttle cruising the LM-2 goes rich around 12.0 and the warm idle is roughly the same 12.0 AFR with an rich exhaust smell. It was set to 14.0 before leaving for the test drive. At this time I can only assume that the power piston spring is too stiff or I do not have enough idle by pass air. More testing.
I must say, another down side to using rhodes lifters beside the noise is the amount of change from warm idle vacuum to a hot idle vacuum.
Thanks
Mark
comp:
cool ;D
Hotrodrobert:
Where are you taking the LM1 reading from? If you have the tailpipe tool, they tend to read LEAN. Seems they get some contamination from the end of the pipe.
Also, you can get the best mileage usually from a slightly leaner that stoic mixture as high as 15.5:1.
No lean surge, good plug readings, test for best mileage will tell.
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