Holley stumble trouble

Apologies for the hijack, but this info may be useful to OP and others struggling with driveability and AFR issues :)

I have been through all those changes, including installing TSRs :rolleyes:
Dialing in my 950

If my t-slot comes in earlier or richer, it's too rich at the top of the t-slot due to the increasing signal (rising vacuum). And most low-speed cruising is on the slot, so a relatively lean AFR is desirable there to keep the plugs clean and get (half-)decent fuel economy. Similarly, cruising on the mains (60 mph/3000 rpm/15"Hg) also has a relatively large contribution from the t-slot due to the small throttle opening required to maintain speed, and AFR there is 14.5-15.... pretty much the AFR is reasonable everywhere except at the very bottom of the t-slot. :realcrazy:

I think the QF just has an inherent problem with t-slot position and length, compounded by a cam that is large for street use... someday maybe I'll go EFI instead! :D


If it’s actually going lean where you think it is, add some emulsion in the middle of the stack. A bit more emulsion will make it richer sooner. It may actually need less emulsion though as it’s probably going rich first. Just my thoughts.