I've been trying to solve this one for a long time, and I've gotten closer, but it's still not gone. Hoping someone has some new ideas.

It's a blowthrough Holley 950HP on a 383 SBC with a 5 speed. Carb has Float bowl extensions.

Here's what I've tried so far:

• Brake Booster: works properly, holds vacuum (Tested with vacuum pump).
• Booster check valve: Works properly
• Vacuum system: no discernible leak, power brakes work.
• Removed jet extensions
• Metering blocks have (always had) "whistles" installed
• Ran tubing between bowl vents to prevent slosh

None of that had any effect. So, I started dropping the float levels. I've got them almost bottomed out now, and it started to improve the stalling ... but it can't stay that low obviously (especially for racing).

Now, the engine will stay running under hard braking MOST of the time. So, because that had an effect, it's almost definitely fuel related, and seems to be fuel slosh (likely out of the air bleeds, because the bowl vents are connected and the whistles are there).

Anyone have any ideas?

 

If you have found a solution, tell us, please.
I have exact the same problem on 650 DP

 

It's the rear float you need to drop (secondaries), not both.

GD

 

I unbolted the carb from the manifold today to find out exactly where the problem lies.
When tilting carb to the front, fuel drips from secondary venturis, not vent tube.

If your secondary bowl fuel level is set according to manual, fuel starts to drip at angle, shown on pic.
I have electrical in-tank fuel pump, so I lowered fuel level one full turn of adjusting nut, seems like it has dropped for +/- 7 milimeters below sight hole.

Haven't tried to test yet, hope it helped.

 

Cool, I ended up dropping mine 1.5 turns and it's a lot better but still not perfect. Just have to crank it back up for the track.

 

Guessing your motor makes pretty low vacuum,.... think that adding a vacuum reserve tank might help ??