Quadrajet Problem Solving > Dialing in your rebuilt Quadrajet carburetor

By Pass Air Needed?

<< < (2/2)

Cliff Ruggles:
If you drill the holes under the mixture screws way out on the later carbs with the metric threads they may not seat as the threads don't go deep enough. 

I've had to tap some of them to 10-32 and use the early type mixture screws with more reach to solve that issue.

For bypass air just remove a small manifold vacuum hose and reset the idle speed and mixture screws.  If it works then add some more bypass air until you duplicate that scenario.....Cliff

gtobob67:
Yesterday I drilled the idle bypass holes to .144. Got the engine up to normal running temp and adjusted the idle to 850RPM. If I seat either mixture screw the idle drops 75RPM. Can't quite stall the engine with both seated but it's close to stalling, running rough. So I do have some control. I only need to turn both screws out 2 turns for the highest idle and best vacuum. So it's still pulling fuel from the transition slots. Minimal odor from the exhaust.  Engine idles at 15" of vacuum now and I have 4"of vacuum at the ported source. The advance unit I have starts at 5" of vacuum so I don't see any advance at all at idle. Took it out for a ride and it is perfect. Idles well, off idle transition is spot on. No surging or bucking at coast or slow crawl. No hesitation at all. Jump on it in 1st gear from a slow roll and it will tear your head off. Time now to put the tools away and go have some fun....

Cliff Ruggles:
Good news!

Navigation

[0] Message Index

[*] Previous page