SO, I just finished fine tuning my street demon 625cfm carb using the kit demon makes-and going by the specifications in the carb manual for elevation and cam lift. It would seem that I have everything pretty optimal. But here's my issue. Throttle response is amazing under partial throttle, gradual acceleration to speed is crazy good. But when I stand on it from a stand still there's a pretty good stumble. Then it catches up and takes off. This only happens when I floor it from the stand still. Driveability everywhere else is spectacular. I've changed the metering rods and the metering springs- and also jetted the carb down one size-again according to the specs in the manual- and I've mixed and matched a ton to get to this point, but can't seem to dial in that particular problem. Am I too rich or too lean still? If I could find that out I might still have some tinkering to do...Engine is a 327 .030 over .491 lift competition cams camshaft, TH350 with 2500 B&M stall converter @ 6300ft elevation, at this elevation I know she's gonna run a little rich anyway-but I've tried to compensate for that. Any help would be appreciated.

 

There's an old rule that all stumbles are lean stumbles. Unless you're seeing a big puff of black smoke out the back, you're lean.

That doesn't mean that you need to change the jetting, but the accelerator pump system probably needs to give you more of a shot to cover the "hole" that happens when you plant your foot in it. Either that or your secondaries are opening too quickly. That's your two main areas that typically cause stumbles when you nail it quick from a stop.

 

Thanks man! I will look into both of those-I appreciate your advise.

 

You might be interested in this article. It goes along with what Damon pointed out:

"This carb also experiences a lean stumble out of the box, though it recovers much more quickly than the other carburetors, and we might be able to remedy the issue with accelerator-pump-squirter or power-valve-spring mods."

http://www.hotrod.com/how-to/engine/...e-new-625-cfm/