Guest Anonymous Posted April 17, 2002 Share Posted April 17, 2002 What? Is that possible.... The idle needle valves are usually just that, a thin pointy needle that fits into a seat, you screw it out to uncover more of the seat and hence more gas (or air, I've never been that deep inside a holley internal orfices ). You're telling me you turn them in to richen them? That would be pretty weird I think, but I'm no holley expert.. Unless they just changed the thread to screw the other way? Regards, Lone Ps: Any way, the way to adjust them is to hook up a vacuum gauge to the intake man. and then turn the screw in or out until max vac. is achieved, I've seen people do it with RPM, but for Holley's I've had better luck using a vacuum gauge as a indicator). Quote Link to comment Share on other sites More sharing options...
Tim240z Posted April 17, 2002 Share Posted April 17, 2002 I've read about these in my holley book (the book is about 100 years old). You just do the opposite as you would do for a regular carb. Tim Quote Link to comment Share on other sites More sharing options...
blueovalz Posted April 17, 2002 Share Posted April 17, 2002 They were changed based on an emissions issue. This type of opposite idle adjustment is easily identified by having a small, clear, nylon ring surrounding the adjustment screw. Quote Link to comment Share on other sites More sharing options...
Guest 1z2c Posted April 18, 2002 Share Posted April 18, 2002 I bought a holley 650 spead bore double pumper. It has Backwards idle mixtrue ajustment screws. Any one know how to adjust these properly. Any help will be great. Thanks Quote Link to comment Share on other sites More sharing options...
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