Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

Lean Carb 2

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Cliff Ruggles:
The engine doesn't have any symptoms of being "lean", lack of power, surging, flat on accelleration, etc.  The crainking pressure sounds extemely high for the combination of parts.

The cam being advanced may simply have the intake valve closing point too early in the cycle, making a lot of compression at lower rpm's....Cliff

Buick 350:
Compression was the clue, and yes the cam was in the wrong position. Runs good now and will run better with a little tuning. thanks for  the help!

Cliff Ruggles:
Good news!

I couldn't imagine that much cranking pressure in a 350 engine with a 232 degree @ .050 camshaft.

I have a roller cam in my 455, 11 to 1 compression, 236 @ .050", and it only squeezes 160psi on a cranking test.

The ICL is set at 109 degrees.........Cliff

Buick 350:
Cliff, your telling me to gain access to the apt screw in the base plate was definitely good info! What a difference it makes in tuning the older carbs. Once I got the right combo of rods and jets the "tip in" procedure was just as described in the book. Recipe #2 with 74 jets and 44 rods, for this engine works well. Now I'm off to dial in the secondary's.

Thanks for sharing your knowledge,
Pete

Cliff Ruggles:
Good news, and yes, it is a very good system if you can get it free'd up.  It was never meant to be "adjustable", just pre-set at the factory.  In most cases the screw will not move, and any attempts to turn it result in breaking it. 

I'm able to get about 80 percent of them out, the other 20 percent have to be drilled out and replaced.

They work best with "B" series metering rods, which have a slight taper on the upper section then taper down to .026" tips.....Cliff

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