Let me start by telling you what I have.

zz4 short block
afr 195 milled 62cc chambers
Felpro 1003 head gaskets
CR estimated at 9.7:1.00
comp cams extreme energy HR XR294HR I /E 294/300 242/248 .540/.562
RPM Air Gap
750DP standard factory jetting and standard 6.5 pv
1 3/4 full length headers
plugs Autolite AR 3934

What I did..

Rebuilt carb cut off air horn. Yes I cleaned it very well

I set the front and rear butterfly to allow .004 clearance between blades and bores all around. Set with feeler gauge. This seems to give good positioning for the idle transfer slots and made all butterflys equal.

Set idle adjusters to give best vacume all are set approximately 1 1/4 turns out.
Vac at idle is about 12 to 15 inches (The needle bounces) Idle is 1,500. This is with the front blades adjusted almost shut. Will not idle any lower.

Engine has not been other than idleing since carb rebuild.

I am happy with idle quality, but want it to be the best it can be.
Now my questions...
Is this a good vacume reading for this combo?
Should I go to a higher PV rating 8.5 or 10.5?
Should I reset rear buttleyflys more so closed to lower rpms?
Are these plugs too hot? AFR recommends Autolite AR 3910

 

Are you getting a dead spot coming off idle? If so, go to a higher # PV.

Vacuum is pretty good for that big of a cam.

You should lower the primary and secondary blades equally to reduce idle speed.

 

I adjusted both blades to set clearance at .003.

Now car idles at 1,250 rpm.

BUT vacuum has dropped to 10 inches

And the passenger side rear idle adjuster screw does not cause any response.

The car is RICH at idle.

I did not change anyting else.

What is wrong??

Could I have gotten a small vacuum leak with the carb to manifold gasket?

Could the rear floats be too high?