Cliff's Quadrajet Parts and Rebuild Kits
Quadrajet Problem Solving => Diagnose a Quadrajet carburetor problem => Topic started by: DougA on June 13, 2017, 01:04:38 PM
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Hello,I have a quadrajet,that the idle increases as it gets hot.This is on a 454 Chevy,manual trans,stock except for slight camshaft improvement.Engine makes 13In. vacuum at idle.Have checked with a matchstick that the idle circuit is pulled in.I don't know the real carb number,as I got swindled on ebay with a restamp.Thought it was a 7040205.Choke works great,car starts great idles fine when cold,car runs good.But after a short time,when I stop,idle is up to 1000-1500,instead of cold 750.Multiple return springs don't help.Have tried disconnected the choke,and wired it open to make sure it doesn't interfere.If I keep blipping the throttle,it will come down some,but rarely below 800-900.Any clues to what else I could check?Thanks
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Could be a number of things but I'd check the throttle body to make sure all the plates are fully closed and correctly centered/indexed.
To idle that fast it's getting a LOT of additional air from someplace.
The original 7040205 was a true factory "high performance" Quadrajet. They had a special calibration, and set up exactly for the 1970 454 manual transmission engine. Difficult to duplicate that calibration unless you are really good at this game......Cliff