Question for Holley tuning gurus

[BobH]

Carb is an older 950hp on a 383 with a 496 stoker kit. Motor shouldn't really matter, this is more of a generic question. What's happening is when at cruise, about 2500 rpm, I've got the air fuel ratio in the high 13s', set by adjusting the main jets. But when I accelerate slightly, like going up a hill, it leans out to 15/16. Not hard enough acceleration to open the power valve, but lean enough to feel it surge. I was wondering what increasing the size of the jets and the air bleeds at the same time would do. If this would help maintain the air fuel ratio where I want it? Any ideas, suggestions?

 

[RemCharger]

Get a lower power valve?

 

[BobH]

currently running a 10.5 power valve in the primary which is about 1.5 to 2 below idle vacuum. At the throttle position/speed I'm talking about showing about 13-14 inches vacuum.

 

[4speed68rt]

Show us a picture of that 950HP.

 

[4speed68rt]

Power valve should be about half of idle vacuum. 65

 

[Geoff 2]

If the main air bleed is removable, I would try a smaller one. That will richen the curve.
If not removable, put a thin bit of wire in it & test.

 

[fourgearsavoy]

Double check your accelerator pump adjustment. The pump shot will fill the lean hole in your light pedal pressure. Make sure it pumps fuel with the slightest movement of your throttle blades. Too many guys adjust it according by the Holley book with a feeler gauge clearance check deal. While this method isn't exactly wrong I have been brought carbs to tune where there is clearance between the lever and the pump arm which will give you a huge lean spot.
Gus

 

[BobH]

Accelerator pump is pretty much zero clearance at idle speed, definitely no slack at part throttle. And it's such a slight throttle movement that any pump shot would be small and brief. It's not a momentary lean, it stays lean until I lift on the throttle. Waiting for air bleeds to get here, when they do I'll try going larger on main jets and high speed air bleeds to try to richen the curve.

 

[BSB67]

What do you have now for Main jets and MABs? What size and number of e-jets?

Larger MAB will slow the fuel response to throttle change. I think smaller would be the right direction.

 

[Geoff 2]

Yes, smaller air bleed. The AB bleeds off the signal [ like putting a hole in a straw ]. Making the hole/AB bigger will delay the start up.
Below from Holley....

 

[hunt2elk]

Before changing the air bleeds, I would try some bigger power valve feed restrictors.