Quadrajet Problem Solving > Dialing in your rebuilt Quadrajet carburetor
still cannot control mixture correctly
77cruiser:
Any exhaust leaks on the lean side?
PonchoVia:
No exhaust leaks.
Ill check the hanger when I get the car back from getting another issue fixed.
When I first got this carb it was a virgin old unit with the calcium deposits in the bottom.
I cleaned it with ospho which worked great, no I'm wondering if there is gunk in an unsee-able passage.
I'll check all this and reply when I get it back.
tayto:
did you pull idle tubes and clean put passages. i did a marine qjet this past summer and not only were the idle tubes plugged but underneath them were plugged as well.
Cliff Ruggles:
I've ran into that issue with Marine units as well, plugged solid in and under the tubes. I've even ran into Marine units with plugged up main nozzles.
They live in a chitty environment so extra care and attention to detail required........Cliff
Cliff Ruggles:
I'd add here that I'm suspecting a fundamental issue someplace since you really aren't getting good results with either combination.
I use the same carb on my own engine and it is set up nearly identical and it is FLAWLESS now for coming up on 30 years.
I actually use it as a "dyno-mule" for engines built here and have loaned it out a number of times for folks dynoing Pontiac engines with stock intakes up at KRE.
To date nothing has outran it, dyno or at the track, and every engine I've sat it on idles perfectly and full control of the mixture screws from rich to lean.
So time to go back to basics, including making sure you don't have a secondary throttle plate xxxxed open slightly, twisted primary shaft, idle airbleed too large, or blocked up passage someplace.
Making 15" vacuum would hardly require any modifications to the idle system with that carb other than a slightly larger idle tube and opening up the DCR's to .055" or so. The big engine will like .110" idle bypass air if you aren't using the hot-air choke system as blocking off that air (converting to E-choke) reduces bypass air some.........Cliff
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