[kyle_blake]

Hi everyone,
I have a QFT 680 HS Vac Secondary I got in a trade, practically brand new, everything appears stock settings 70/74 jets. Main Bleeds #28 , all as per :

https://www.holley.com/products/fuel...arts/HR-680-VS

All new rebuild kit installed, no blocked holes, no passage ways blocked.

The crazy thing is I have never had a Holley carb continually no matter what run rich at IDLE 11.0-11.5:1 ratio with idle mixture screws essentially doing nothing to get me leaner unless almost bottomed out.

yes timing , plugs and everything else is good. just rebuilding another carb.

What I've done:

√ 1/2 turn out from bottom on 4 corner idle screws
√ Rear Idle screw set so idle is roughly 850 RPM
√ Primary Idle Screw only turned CW 1/2 turn from bottom
** So front rear transfer slots should be relatively close however I'd have to flip it and check.

I actually came from the rear idle screw completely backed off and figured I may as well add more idle to see if that helped.

√ Float levels perfect front and back. Tried lowering them but did not affect AFR.
√ Fuel pressure is perfect.
√ The Main Air Bleeds are stock 28's
√ 6.5 PV tested as well, holds vacuum gasket used

I'm at a loss, I can't turn the idle screws in any more and expect that 1/4 turn out is "normal" range or practically bottomed out.

I really think this carb is out of the box settings and a bit surprised the troubles its giving.

My only guess is changing the idle circuit screw in each metering block to something smaller? (as seen in pic) ??

Aside of closing off the rear idle mixture screws and just running off the front which I'm trying to avoid.

Thanks for your help.