Quadrajet Problem Solving > Dialing in your rebuilt Quadrajet carburetor

Recipe #1 Question

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Tuffnut:
Recipe #1
Cliff, I'm trying to follow your recipe #1. My carb is a 1975  7045250 with the aux piston/rod. I bought the kit off you to plug the aux piston hole which i did, plugged the aux rod jet with the lead sinker, new accel pump, new needle & seat, new heavy spring for the power piston and replaced the existing .067 jets with the new .073  jets and .041 rods with the new .044 rods for .029 difference between the jet & rod. Also adjusted the float to 1/4" from 7/16" as per the book. Had it started up runs good at idle and responsive. Slight hesitation around 1500 rpm . Too snowy here to take it right now for a rip. Car runs 1975 350 olds with rebuilt #5 heads, 16" vac with and Rv cam, Dual exhaust, new pistons bored.030".

Should I be looking at the main air bleeds for proper opening of .070" ? I can't get my head wrapped around which ones they are by the book compared to what I have . Picture attached of the the actual carb body
Thanks
Jeff
Paris, On.

Cliff Ruggles:
Leave all the airbleeds at the stock sizes for that carb number.  Once the weather permits do some testing, you'll probably find that it woln't need any further tuning, but you can add some fuel using the APT system if/as needed........Cliff

Tuffnut:
Thanks Cliff for getting back to me...
Jeff

Tuffnut:
Cliff after doing all the mods and doing some testing, the carb is running a bit rich at cruise.
There is no hesitation, no black smoke that I notice. When I do the tip in at 2000 rpm the engine drops rpm right way and same if I take off an vac line to the carb. It has lots of power though. I'm using .073 jets and .044 rods I got from you. My aux piston is closed off as per the parts from your kit. Adjusting the aneroid doesn't make any difference right now.
Weird part is I get slight surging at cruise, doesn't make sense if it is rich. I reset float back to 7/16" as well. Power piston with the heavy spring is working correctly, verified with the straw check, doesn't start to lift until around 2000 rpm under load in drive. Idle vac is around 16"-17"

I was thinking of going down one jet size which i have .072. This would affect cruise & WOT.
Problem is, I can't tell if I'm too rich at WOT. It's possible I may be as well.

Is it possible I may have to go up to a .045 or .046 rod instead?
These early aneroid 1975 carbs are not friendly. Not ready to throw in the towel yet.

Not sure which way to go, down 1 jet size or up a rod size.

Jeff

Cliff Ruggles:
I'm not fond of those here and have had issues with enough of them to avoid them when possible.

It's a poor design as it has drilled passages leading under the jets to allow them to see each other, plus the length from the aneroid located APT to each jet is not the same.

Surging would indicate a tad lean at cruise or too much timing from the vacuum advance.

Dropping back to 72 jets will lean it up a tad at part throttle and a little and heavy/full throttle as well.  I'd try that first.

I've typically had to go smaller on the primary rods with those vs larger from the 73/44 set-up.

Make absolutely sure the power piston hanger arms are level and exactly even, big player there in what you are doing......Cliff

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