502 stumbles and poofs through carb - Help!
 

I have (2) modified 502's and (1) is misbehaving. When I swap carbs the problem is transferred to the other motor so it is carburator related.
The suspect carb idles fine. Once I drop in gear and attempt to throttle up, it starts to boog and poof through the carb and then stall. If I work the throttle back and forth I can manage to get through it and get up on plane and once the motor gets past 3000 rpm it is fine. the plugs look light tan colored and I suspect maybe lean condition exists. Any help for be greatly appreciated.
What do I check for?

Here's more info:
Holley Dominator 1050's
Single Plane Merlins
Comp Cams 650/660 lift, 278/288 dur
CMI headers
Ported iron heads with 9:5:1 comp

Re: 502 stumbles and poofs through carb - Help!
 

accelerator pump

Re: 502 stumbles and poofs through carb - Help!
 

I would guess accelerator pumps also. ? Is that duration at .050"?

Chris

Re: 502 stumbles and poofs through carb - Help!
 

Rebuild it. probably the accellerator pump. May have a cracked diaphram. Check for an external leak to avoid a "boom".

Re: 502 stumbles and poofs through carb - Help!
 

I love this board. Good people always willing to help!
Appreciate the responses everyone. :cool:

Re: 502 stumbles and poofs through carb - Help!
 

Could be a couple of things, but I'd focus on the accelerator pump. It's sole purpose is to cover a temporary lean 'hole' when you open the throttle. Could be the adjustment of the actuating arm, the capacity of the pump (cc's) or the profile of the actuating cam.

Re: 502 stumbles and poofs through carb - Help!
 

Another part of the accelerator pump circuit that I have had problems with is just under the jets that spray the fuel into the carb from the accelerator pump is a ball. Sometimes this ball sticks & will keep fuel from being injected into the carb.

Look down in the carb & move the throttle, If you do not see fuel spraying you have found your problem.

Re: 502 stumbles and poofs through carb - Help!
 

quote"Look down in the carb & move the throttle, If you do not see fuel spraying you have found your problem."
Then replace the accelerator pump!