Car falling flat at 1500rpms and then recovering

[Gordz32]

Heys Guys, We've got a chevelle here at the shop equipped with a 454,vortech supercharger, and a m-22. Its got a 4150 in the box and the issue is that there is a flat spot where the car fall flat on its face at 1500rpms up to 2100rpms. If you keep your foot in it it will act like its playin catchup and lurch forward once it gets past those rpms. Any Ideas?

[justincat]

Is it vac. secondary. A larger squirted for a longer fuel shot may be the ticket. Have you made sure your getting a full shot of fuel at instant throttle movement, you might just adjust your acc. pump. A little more timming may also take this out.

[Gordz32]

Its a double pumper so no vac secondaries.

[hotrodf1]

How long of a time is it falling down? Are we talking a brief sputter, or a prolonged (couple seconds) period of stumbling?

Does it happen while you are moving the accelerator pedal, or does it happen while the pedal is held at some throttle opening (15 - 25% or something)?

What has been done to the carb for the SC appication? Air bleeds changed? Jets?

What happens if you just nail the throttle? Does it take off fine, or still stumble.

What kind of ignition system, timing curve, do you have boost retard, etc.

If you can provide some more specific details of the condition perhaps I, or someone smarter than I, can help you out a bit.

I did a DIY Vortech Blow Thru application on mine so I've had a little experience setting things up, though I didn't have this problem you speak of.

Do you have a wideband by chance to see what's happening AFR wise?

[Gordz32]

I found the problem. The guys who built the car didn't prep the carbn for boost and the floats had collapsed