Here's my original request to Holley for some info...


Your Question Was:
Slayer 600: Excessively rich idle and WOT

Idle mix screws only 3/8 turn out, but still 12:1 idle A/F, cant get it to target 13.5. Engine runs excessively rich cruising anywhere below 2300 RPM, but then leans out nicely to 14:1 at 2500, then falls below 11:1 any time the secondaries are open. I have already backed the secondaries down to #71''s. Main jets were fattened to 70 to get the 14:1 before secondaries open. Previously was 15:1 or higher with 68''s. I need to restrict down the idle system.

I know I can increase the idle air bleed size to get the mix screws back in range, but I would like to know the factory idle feed restrictor size to test reducing it as well. PV has been checked and is not blown.

Thank you,

Dan


Holley's response:
ifr .031



WOW. Thanks Holley.



Yes, cruise vacuum is high teens at just about any speed. Verified 18 at 2800 rpm steady state doing 80 on level ground. I dropped the PV opening for a few reasons. Whether they are correct or not remains to be seen.

1) The engine is not high power, meaning even small accelerations require a fair bit of throttle, dropping the vacuum significantly and hitting the PV unnecessarily.
2) The PV was dumping in so much fuel is would go from 15:1 to 11:1 with the factory .052 PVCR's. That doesn't work AT ALL with mild acceleration.
3) The secondary bog seemed to be from opening too soon, so as I delayed the secondary opening to a higher load/throttle position, I moved the PV opening with it.