Quadrajet Problem Solving > Dialing in your rebuilt Quadrajet carburetor

turbo to non turbo considerations?

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Cliff Ruggles:
A drill press is NOT wanted, needed or a good idea for drilling anything on a Q-jet. 

The bypass air slots are in place, just not drilled.  "Free" drill them with the baseplate on a wooden block with a small hand drill, it's not fussy.

I do NOT recommend drilling the throttle plates on Q-jets that have the idle bypass air system in place.  It is a very precise controlled vacuum leak, use it if/when you need idle bypass air.......Cliff

F250 Restorer:
Thanks, cliff. I started with 70 thousandths. You're right. Easy.

Hey, I tried to test the pwr piston spring by taking the main body section and applying vacuum with a hand pump to the hole on the bottom, with only spring and piston in place. I could not get vacuum. Am I doing something wrong?

quadrajam:
I dont think a hand vacuum pump could keep up with the leakage around the power piston.
Maybe use vacuum sourced from a running car engine.
Or get fancy and try using a junk main casting, drill through the bottom with the right bit
and drive in a vacuum nipple. use a tee and install a gage very close to the casting. Then
run a longer piece of tubing to the car. use another tee and a needle valve to control some
bleed in air to vary vacuum at the casting . Never got around to trying this.Let us know how
it works.

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