Rebuilt and installed 292 in my 66 truck. Engine has been run in and timing set at 8 deg advance. Engine seems to be running fine but cannot get idle under 1200 rpm even with idle screw as far back as it will go. Idle mixture screws do nothing when turned (assume due to high idle). Have checked for vacuum leaks and unable to find any. PCV hose hooked up to carb and distributor vacuum hose hooked up after setting initial timing.

Brand new Edelbrock AVS 500 cfm carb, Engine is lump ported, ~9.4 compression, Clifford intake, Langdon dual exhaust, lumpy cam, GM HEI.
Assume its a carb adjustment of some sort.

Any thoughts on how to get my idle down? Thanks!

Could be an indication of a vacuum leak, double check the carb baseplate and intake manifold to head fitment.

Thanks, I'll recheck for vacuum leaks. I did decide to plug off the PCV valve to see how that impacted idle because I'm not certain I have the correct one. (Didn't realize that some PCVs pull more air than others). Anyhow, that dropped the rpms down to ~1050 but still way off and idle screw completely screwed out. Do the step up springs within the carb impact idle since they are actuated based on vacuum?

How much vacuum is the engine making at idle?

If you pull the vac. line off of the vac adv pot on the dist - does the idle slow down?

I don't have a vacuum gage. Will recheck the idle when vacuum hose removed from distributor but now that you mention it, believe the idle did not go down when I last tried. Unfortunately, I tried multiple things today and they are now blending together!

I had this problem with my new Holley. It was the choke idle setting too high. It's a screw that's really hard to get to, I used a mirror. It did the trick for me.

Mark

Thanks for all the input.
I spent today trying to find vacuum leaks without finding anything. Also checked fast idle - nothing. Used carb cleaner trick etc. I decided to swap out with my buddies edelbrock 600 and now after minor adjustments to idle mixture the engine idles and runs fine.

Believe my brand new out of the box carb is defective. It looks like the secondaries don't quite close. Who knows what else. I could put my hand over the secondaries while running and it would idle down.

I've had this carb sitting in the box waiting for my rebuild since winter.
Any experience with edelbrock repairing or replacing in a case like this? Thanks!

you secondaries are adjustable i believe. there should be an owner's manual on how to adjust them.

Thanks TJ. This AVS carb is different than the Performer and decided to switch. Looks like Jegs will refund my money. The rpm with the AVS just wasn't adjustable and believe it was defective. Or, I just wasn't able to figure it out :-)


Next on the list is a different 3 spd until I can get my t5 installed. My Saginaw started making loud mechanical noise, vibration ( input shaft bearing shot?). Noise goes away when clutch is depressed. Throw out bearing looks and spins fine when accesed through the clutch inspection plate. Had a gear oil leak and found it was down about a half qt when i caught it. Slowly going through this old truck. Replaced rag joint earlier this week.

Returned the Edelbrock AVS and installed 500cfm Performer today. Seems to be running well; certainly better than the AVS carb. I really think the AVS carb was defective out of the box. Absolutely no issues with the new Performer thus far but need to drive it a bit more.

Tune it up and post a burnout video! lol

Tune up is next. Replaced points distributor with OEM HEI and engine seems to fall flat at 3000. Engine runs rough when straight vacuum vice ported is used on the distributor. Assume new springs and vacuum canister adjustments will be the next thing to figure out.