High RPM Stumble

[Freakkiller]

I have a W72 Trans AM with a Quadrajet.  It runs well / starts well...idles fine.  At @ 4200 RPM, the car loses power...almost like a spark issue.  I think it is fuel.  I do not know the specs on the rebuild of the motor as it was done before I owned the car.

I think I need to re-jet the secondaries, I purchased the book from Amazon...but was looking for ideas on how to incrementally increase jet size until if does not stumble.

Can this information be found without the specific specs on the motor.  Or will I have to open it up in order to get the right jetting.  Thanks for listening.

Marcus / Freak

[carmantx]

There are no secondary jets in the quadrajet.  You have the secondary rods that are on the hanger assessable on the top rear section of the carb.  You may have a float setting too low.

Provide as much information as you can about your engine, car and the quadrajet.  What is the code number on your carb, found on driver side above the secondary shaft on main body.

[77cruiser]

Might be time for a new fuel filter.

[Cliff Ruggles]

The problem will be fuel delivery, and nothing to do with tuning.  You are simply sucking the bowl low/empty on hard runs.  Many things can cause this, usually it starts with the wrong fuel inlet seat being installed, plugged filter, weak fuel pump, restriction in the fuel system someplace, etc.....Cliff