Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

7041251 tuning...

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Kenth:
Problem is likely the cam, too much duration, too tight LSA acts like a vacuum leak at idle/low speed.

You may try at least .042" idle tubes and .095" idle needle holes.

lightning boy:
It is because you don't have your engine at stock settings. It didn't come from the factory with 130 PSI compression.

Tancuda:

--- Quote from: Kenth on December 16, 2025, 02:34:06 AM ---Problem is likely the cam, too much duration, too tight LSA acts like a vacuum leak at idle/low speed.

You may try at least .042" idle tubes and .095" idle needle holes.

--- End quote ---

Ok thanks will check on this. Idle needle holes, you mean the holes behind the mixture screw ?

And I just realize that on the picture, my primary throttle blades are drilled !!

I saw a lots of quadrajet on the web, but never saw drilled plates (stock).

Any ideas ?

Tancuda:

--- Quote from: lightning boy on December 16, 2025, 04:44:37 AM ---It is because you don't have your engine at stock settings. It didn't come from the factory with 130 PSI compression.

--- End quote ---

Ok thanks, but what do you think would be good numbers for a 1970 455 low compression engine ?

At least there are no more than 10% variation between cylinders.

77cruiser:
I'd think about 160 for a stock engine. Maybe the cam was installed retarded.

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