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Holley Idle 2 schools of thought

696 Views 15 Replies 5 Participants Last post by  PRNDL
So which school of thought do you guys recommend as far as idle is concerned?

Secondaries closed with just a small 1/8 turn to prevent binding. Then set the idle via the primaries only?


Secondaries adjusted to match the exact same level as the primaries. Then make idle adjustments by adjust both fronts and rears the exact same?

Both methods assume the primary transitiin

AED Holley 750 HOHP DP 4 corner idle. Came with 1/8 holes in primaries only. and PCV hooked up. One inch open spacer.

The engine is a freshly rebuilt 383 stroker. All machined, brand new stroker internals, 30 over, zero deck, 6 inch rod Skip White unit with 10cc dished pistons. AFR 195 heads, Performer RPM AIR GAP, dual plane, and Comp Cams XR282HR 230/[email protected] 110LSA CAM. HeadersBreak in has been completed.

I’m noticing that if I set my idle to 900 rpm via the first method, primary adjustment only, my rear idle mixture screws stop responding. I can screw them in all the way and no change.
When I set the idle via the second method, primary and secondary matching, to 900 rpm, the front mixture screws stop responding.

I’m thinking of lowering my idle to 800 rpm.

Any ideas?
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· ******* Professional
1,709 Posts
I would call AED and put it back to original for starters.

I just went through this with a Holley Tech on my own Quick Fuel SS-830 in an attempt to get consistent cruise AFR at different RPMs on the street with a milder cam than I have been running for a while (Comp XS274S) Would be 14.0 AFR at 2500 but cruise would get much richer (and richer) as RPMs went up. Never really cared much when racing as full power AFR was OK - but now on the street.......

Talked to a Holley Tech for starters, since I had jacked around with the secondary opening when I first got the carb. Went to secondary blades just barely covering transfer slot. Primary blades set so transfer slot is a square. Put original IFRs, PVRs, and main/secondary jets back in. Went from there but left the secondary throttle opening alone. It fixed the inconsistent cruise AFR and best of 18 mpg so far.

Point is that I've realized that you can't just change secondary throttle openings willy-nilly as you can change the carb calibration completely (and not for the better) by doing so. For yours I question why AED drilled the throttle plates for a fairly mild XR282HR, but they are the carb builder - I'm sure they had a reason (and this would certainly affect other choices that they made). I would suggest you get things back to as-built. After all, it's a custom carb built just for you! (or did you buy it used?)

Doesn't an open 1" spacer defeat the purpose of a dual plane manifold?

Your build should be killer!! This is the sleeper Nova, right?
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