Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

new to forum. have issues with rebuild on new motor

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soe1:
My timing is setup at 18 initial. Although the motor seems to like 22 degrees the best. distributor vac is on port vacuum. I have stiff springs in the mechanical advance and it still hits 38 degrees total before 3k.  I will check the mixture screw threads(what size tap is that).  This carb does seem to have large transfer slots as well. What can I do about that? I no longer have nozzle drip since I drilled out the idle bypass to .112.   Thanks again  soe

Cliff Ruggles:
Do you have any control with the mixtures screws?

The idle system feeds the main system at low throttle openings thru the mixture screw holes and the transfer slots.  If you get too much fuel coming in it will make it pretty "fat" despite small jets and larger metering rods, especially at 5000'.

Hopefully you used our parts for the rebuild, good parts make for a better end result with these things.

Even the jets being sold by most places are NOT for the Quadrajet and will throw the calibration off simply because they do not have the same internal specifications.

I'm also NOT a fan of big cams on tight LSA for street engines.  I've been in this hobby for nearly 50 years and the biggest complaints we get and problems we see are from folks using tight LSA and too much duration for the CID and compression ratio.

Matter of fact, with the engines we've built, dyno'd and drag strip tested here over the years, the wider we go with LSA the more we are rewarded with smooth idle, strong power off idle, more average power, stronger upper mid-range and top end power, and better track numbers.

Big cams on tight LSA's in contrast delivery crappy idle quality, stinky exhaust, narrow power curves and poor efficiency in the "normal" driving range.

Those statements apply to real street/strip cars, not full race stuff......FWIW.....Cliff

soe1:
Cliff:  I do not have any control with the mixture screws. From your previous suggestion, I would like to tap the holes further into the baseplate. Do you happen to know the tap size? I agree with your comment on the cam choice. Although, I never have had an idle problem. I get about 12" vac. and the motor seems like it wants to pull real hard from 2k-5k once the fuel clears out and stops loading up. I think you are right about the idle system fattening up the low throttle. so, if I tap the mixture holes and get the screws to seat shut with this slow down the transfer slots feeding fuel?  soe

77cruiser:
You can try to mark the needles with a marker & screw them in all the way & see if they seat. Try it with the spring off too. 85 year is probably metric threads, real fine.

soe1:
Thanks Jim: I will try the marker trick and see if the screws are seating. If not I am going to tap the holes until I do get a full seat. I think the screws are m4x.5 pitch.
                                                                                     thanks again soe

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