Weird problem setting idle on '67 L79

[Joe C.]

Re: Weird problem setting idle on '67 L79

To be clear, the manual specifically says to adjust for maximum vacuum. The only time the term "lean roll" is used is in reference to Rochester BV carburetors.

Adjust for maximum RPM/idle vacuum and then back both screws out an additional 1/8 turn. This will enrich the idle mixture slightly and will help to cover up your cruise stumble. Every time you adjust the position of the pri throttle blades, on a single inlet Holley, you should re-adjust the accel pump clearance because the pump arm will be at a different position on the pump cam.

If the air filter element causes a mixture change at idle, then it would be so restricted as to choke the engine at higher RPMs. Preposterous! Installation of the air filter should have absolutely no effect on idle speed. If it does then the idle circuit is waaaay too lean (which is why smog engines' carbs are adjusted with the air filter ON), and/or you have a vacuum leak somewhere. Lean roll is an aid for tuning smog engines...............idle mixture was deliberately set to produce a lean misfire at idle.

Make sure that both pri idle air bleed metering holes are clear and clean.

[Dennis O.]

Re: Weird problem setting idle on '67 L79

This is not what the Chassis Service Manual says. As I said before, my car runs and drives perfectly with the carburetor adjusted per the manual. I've found that the engineers at Chevrolet knew what they were doing. I consider this case closed.