General Category > Quadrajet Carb Talk and Tips
Idle Bypass Air ??
77cruiser:
What's your fuel pressure & float level?
omaha:
ok i think you are getting close cause 1000 rpm is a lot better than 1350. Just wondering if your primary plates are still closed all the way. That is where I was getting confused because usually they should be open a bit, exposing part of the transition slot. If they are closed all the way that means all the air is coming through the bypass holes or someplace else, (like a vac leak or incorrectly indexed plates {the plates only fit one way correctly to fit the bore} you should not be able to hardly see any light around the plates if you hold them up to a light with the plates indexed correctly). Not sure about the wet nozzles as it would seem if the plates are closed up that much that there would not be too much of a signal to affect the main circuit. Maybe the plates are not correctly indexed which could affect all of the problems that you seem to be having. It is possible if the plates were not indexed correctly, that might cause a "pull" on the top of the transition slot due to the gap around the plates, causing the nozzles to be wet. But I am just thinking out loud here because I have never seen that happen. The idea is to have the bypass holes and also be able to adjust the idle with the screw for the idle adjustment. the mixture adjustment plays a part here also as this can increase or decrease the idle rpms to a certain degree. Its best to use a vacuum gauge to set the idle mixture. the correct mixture will have the best vacuum reading. I guess keep plugging away at it. I am thinking that you could get it to idle at 850 to 900. It's frustrating I know especially after all this time but you are getting some valuable on the job training.
beertracker:
I am still working on the q-jet but disaster struck today. The threads gave way when I was installing a 2.94" x .184" bolt (screw driver slot) in the base plate. I think the base plate is made of aluminum? I didn't even tighten it down the threads just gave way. So how do I repair this threaded hole? Use the next larger diameter bolt keeping the thread pitch the same?
beertracker:
Here are answers to earlier questions.
vacuum is 12 to 14" Hg. it varies with idle speed.
float height is 1/4" at toe per cliff.
fuel pressure fluctuates 7 to 8 psi. my fuel pump is a oem mechanical. No pressure regulator. already had a regulator conversation with cliff. idle bypass holes are at .113". Should I go bigger?
Some where during all my testing the primary drips re-appeared. I doubt if they ever went away because of poor lighting in my garage resulting in I couldn't see. Primary blades are fully closed and very little light is visible between blades and barrels. I think the blades are ok. APT orange spring is working. I can see the primary rods move under spring and vacuum conditions.
I think I am approaching the end of this project. One last thing I could try is to swap out the intake manifold. Maybe that's the source of my air leaks.
429bbf:
bt --i don't know squat about a pontiac .ive got a 460 ford set up on the low end of recipe 2 8.5cr 262 iske cam and with the compression i have i can't burn all the fuel. I'm fixing to change heads and get about 10.2 cr and then ill tune the carb as needed .it seems with your setup if you bumped the cr another point thing would run better. maybe I'm wrong . will some of you pontiac boys chime in and correct me because my buddy is fixing to work on his 455 and could use a little advice as to what setup works best for all around driving (no drag racing )fwiw 1976 grand prix
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