General AFR Guidance (Holley Tuning)

goldduster318 said
The idle thing on power valves is garbage, IMO. That has not much at all to do with what PV you should use.

How I do it, is drive around with a vacuum gauge hooked to the car. Load it down in high gear and go up a hill. When the engine starts to go lean, read the vacuum on the gauge. Record this and find the nearest lower number power valve. I bet you'll find the car likes something more in the neighborhood of an 8.5 power valve.

Considering I had one of the more difficult possible combos with a carb (340 with a 227/231 @0.050 roller cam, 750 dp, 4-speed, and 3.23's), this worked well.

IMO the car should idle between about 13.5 and 14.0, Power should be 12.5-12.9, and cruise can be as lean as 15.5:1 at very light throttles. This is what I run with EFI.

Thanks for the input. I've still been fighting this lean stumble. It's got the 6.5 PV in it now, but I think you're right. I'm thinking a bigger one would work better. According to my AFR gauge, it goes really lean when I lean into the throttle in high gear, which causes the stumble. pump nozzle is a 40 with orange pump cam. I may see if a blue cam would help as well.

I still have to work through a couple other suggestion from earlier posts in this thread as well. It's getting closer, but the stumble is still there. I've had this issue with a holley before. Maybe it's just a street avenger thing. Good thing I've got a couple double pumpers to try out as well.

goldduster318 said
Another thing that will cause stumbles is not enough ignition timing. Hopefully you've done the "timing with the highest idle" method and then backed off the total advance to 32-36. Depending on your combo I'd expect the initial timing it likes to be between 15 and 24. Mine seems to like 22. My old 360 liked about 18.

I've got timing set at 28 initial and 36 total. Seems to run well at that timing combo, other than the annoying stumble of course.