half throttle stumble help!??

[My427stang]

Recommend going back to stock setup for all values, including jetting and powervalve (6.5 is stock, but I also agree a 7.5 will work great here)



One of the the things I see most with a Holley is when guys start chasing tuning issues is usually a float level issue

The idle, transition, and main jet circuit are all very sensitive to float level issues, the higher the float level, the easier for the circuit to "energize"

If it were me, I'd return the carb to bone stock, ensure the accel pump was adjusted correctly to .015 of clearance at WOT, and ensure my initial timing was 10 BTDC or greater, then set float level to were it runs out of the float sight plug.

Not "rock the fender and make it come out" but a clear level to the bottom of the hole at idle.

Then I'd run it and see what I had, often an addition 2 "flats" when looking at the adjuster nut higher than coming out the hole will make all the difference

I will say that your jet changes did nothing because it was the wrong circuit, you are fighting a transition circuit issue and you were soliving it with main circuit fuel, apples and oranges

Get it back to stock, verify timing and let us know what you come up with