Quadrajet Idle Speed Screw Questions
- Thread starter MrSony
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It is very difficult to diagnose Qjet problems over the internet because we do not know what has been done to the carb and or engine. Rough guess you have either a vacuum leak problem which can even include bad intake manifold gaskets, idle circuit problems, or throttle valve issues.
The carb is 100% stock. Just been rebuilt with stock new components from a kit from quadrajetparts.com. I've built a handful of qjets, so I have a deeper understanding of how they work than the average Joe Blow shadetree mechanic. I found that there was a fast idle (ONLY ADJSUTABLE WHEN CHOKE IS ENGAGED RIGHT WHEN THE ENGINE STARTS) screw UNDER the choke housing that you have a small window of time in which to adjust it before the engine gets to operating temp. Then when the engine is hot at op temp you adjust the idle by the idle screw by the throttle linkage. Got it to idle at 900ish in park when cold, 800 when hot. 600 in gear. That was my issue.
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Also engine is a stock rebuild other than a three angle valve job on the heads, comp 268 .469/.469 cam and a .030 overbore.
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I have a document that addresses idle issues and things to check. You can download it from the rference tab on my website or I can email it to you if you would like. It may be helpful.
https://media.wix.com/ugd/d12fb6_65cd2a2ee7814147862fcd5203a9c7d0.pdf
https://media.wix.com/ugd/d12fb6_65cd2a2ee7814147862fcd5203a9c7d0.pdf
Thanks man! I'll be sure to check that out. I think I also have a small vacuum leak. When I got the intake there was a block off plate over the hole where the divorced choke was, but it made out of really thin metal and there is so much pressure there it pushed it up and I think that's part of my problem. Anyone know a place that makes a block off plate for BUICK 350s, or do I have to fashion my own? The metal that is on there now is around the thickness of a dime.
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