New Motor High idle

[F-BIRD'88]

Edelbrock carbs mount inline and use simple linkage on that setup.
But I also am not suggesting at all you run out snd spend $$$ on any right now....
Secondary metering plate may have wrong idle fuel metering hole size "secondary IFR" or blocked idle air bleed.
Metering block gasket cross leak.
Blow out air bleeds with compressed air.
Do the cylinder balance test.

[PRH]

That... That was the reason for the 660 center squirts. Say what you will but they still work awesome..

Really not my favorites....... but I do agree they would probably have no issues with idle quality in a combo like the OP is running.
They’re 2 corner idle, but they’re calibrated for the big cam, large plenum, dual carb situation.

[F-BIRD'88]

Reduce idle spark timing to 24 degrees.
Reset primary throttle idle speed and pri mix screws.
How far turned out now?
Mix screws reactive?
Primary throttles are open further now.
More T slot exposure at idle.
May now (or may not) need a (dummy test) pcv valve on one carb.
(3/8" pcv vacuum port on carb base not on intake)
This gives more air at idle.
Changes the throttle idle position.

Temp test setup.....

[RD_Racing]

For reference, here is what these carbs have. They are basically Quickfuel Slayer 600vs that have been modified and suppose to be setup for my application after I gave them my motor specs....

FEATURES:
MODIFED QUICKFUEL MAIN BODY, CHOKE HORNS HAVE BEEN REMOVED AND THEN BLENDED AND PLOISHED
INSTALLED DOWNLEG BOOSTERS
TRICKED OUT FRONT METERING BLOCKS
SECONDARY METERING PLATES INSTALLED THAT GIVES YOU ADDITIONAL JETS IN THE REAR
ADJUSTABLE VACUUM SECONDARY HOUSING
IDLE AND HIGH SPEED AIR BLEEDS
4 DOOR POWER VALVE
HIGH FLOW NEEDLE AND SEATS
CLEAR SIGHT GLASSES - TO HELP WITH FUEL LEVEL ADJUSTMENTS
CAST ALUMINUM MAIN BODY WITH 1-9/16 BORES
POWER VALVE BLOWOUT PROTECTION

Here is what they came with:
Pri jets #68
Sec Jets #78
PV 3.5
PV Secondary plugged
Primary Nozzle #31
Sec Nozzle N/A
Acc pump 30cc
IAB .070/.033
Hi Speed AB .031/.031

Here is a video I did just before it started to rain today.. Sorry its sideways, LOL
https://www.youtube.com/watch?v=ALrrZ_T_Afs&t=6s

[RD_Racing]

Reduce idle spark timing to 24 degrees.
Reset primary throttle idle speed and pri mix screws.
How far turned out now?
Mix screws reactive?
Primary throttles are open further now.
More T slot exposure at idle.
May now (or may not) need a (dummy test) pcv valve on one carb.
(3/8" pcv vacuum port on carb base not on intake)
This gives more air at idle.
Changes the throttle idle position.

Temp test setup.....

It wont even run with the initial set at 24 degrees.. Anything below about 28 it doesn't sound right at all. And that's just at idle..
Im currently at 40. I was at 34 but it seemed to get better as I increased but didn't seem any better above 40 so I stopped there..
Right now my mixture screws are closed. If I open them at all, the idle starts slowing down and vacuum starts dropping and you can hear the idle quality going down.
All vacuum ports on the carb have been plugged by the carb builder. He told me run my trans off the manifold port and run evac system which I have..

[F-BIRD'88]

The carbs were designed to use a pcv to get correct throttle idle position and T slot exposure at idle so the idle circuit works right.
Get the carb builder to fix his work.

The pcv does not need to be on the valve cover for this.
The pcv air flow is what allows correct TSlot exposure throttle position at idle.
If when eliminated it throws off throttle position and the whole idle fuel curve.

[F-BIRD'88]

A fixed oriffice or a adjustable valve ortifice (that includes a anti backfire burn back safety valve inside) can
be substituted for the pcv valve to get this extra air flow.
(Same as a "idle eze" but external)

Did you do the cylinder balance test?

[PRH]

Well, for me it sorta comes down to this........

You’ve got the motor idling with the mixture screws all the way in.

It’s as simple as, “what’s wrong with this picture”?
Until that situation is rectified, imo, you’re just pissing in the wind.

When the carbs are set up so the best idle is achieved when the mixture screws are within the normal range....... it’ll idle stronger/better.

Of course, if it was primarily a bracket car........ it probably doesn’t need to idle any better than it does now.

[F-BIRD'88]

Is another car/engine (any) available to test try each of your carbs on?