Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem
Dieseling
Kenth:
Use the correct throttle body gasket and your idle bypass air will be fine. Wrong gasket will block the hole on passenger side on your throttle plate.
Chevynation:
--- Quote from: Kenth on October 19, 2023, 02:00:18 PM ---Use the correct throttle body gasket and your idle bypass air will be fine. Wrong gasket will block the hole on passenger side on your throttle plate.
--- End quote ---
I currently have the 7038396. That’s why I had to shave some of the gasket so my manifold vacuum port would work.
Kenth:
You are using the correct gasket for your plate, no "shaving" should be needed.
Pictures of your shaving?
Chevynation:
--- Quote from: Kenth on October 19, 2023, 11:54:12 PM ---You are using the correct gasket for your plate, no "shaving" should be needed.
Pictures of your shaving?
--- End quote ---
The holes were completely covered before I trimmed. I cleaned the gasket up a little bit so it didn’t look as ragged.
Chevynation:
Found an issue. I’m only measuring 3” vacuum at the manifold vacuum port on the carb but I’m getting 10” at the choke pull off port on the carb. I pulled the tube out of the side of the carb for the manifold vacuum and it’s not blocked or anything. Before I shaved the gasket it wasn’t getting anything because it was blocked but now it’s so low that even my aftermarket vacuum advance can can’t add timing at idle. It’s not a straight shot down through the gasket from the main body bypass holes to the base plate. There is a recess in the base plate or main body I can’t remember which and the bypass holes are offset because the main body is in a different location than the baseplate due to the year difference but since there is a recess air should still get by I would have thought. I could easily blow air through the manifold vacuum port now whereas before I could not. Not sure what I could do to be able to use vacuum advance besides using a tee fitting at the choke pull off.
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