I am working on a fresh mild 440 in a 69 Coronet RT 4 speed. It has a new Thunder Series AVS 800cfm carb. It performs super except for a very slight tip in bog or pop back throught the carb. (lean?) under VERY light acceleration at about 1000RPM. Moderate throttle or harder it is not there. It is NOT the secondaries.

I have the accel pump in the closest (rich) hole. I have richened it one jet and about as far as I can with metering rods on the low speed side. I have the springs in it to move the metering rod sooner (pink). It has helped, but I cannot completely eliminate the sag. Any ideas?

THANKS.

IIRC the natural colored springs are the stiffest. I'd switch to those.

There are also different pump shot nozzles available,though I'm not sure what size comes in teh 800cfm carb.

Raise the float level.

On Edelbrocks site in the troubleshooting section, they mention a slight bog at just off idle was caused by having the Idle Mixture Screws not set quite right.

Probably something about the transition from idle to primary jets isn't right.

I'd check the initial timing, the idle speed, and the mixture screws as mentionned. Not sure where you are interms of rods, but if youcan get the same full throttle (3rd step on the rod) size with a slightly smaller 2nd step, that might help too.

You'll want at least 13 degrees initial timing. When I ran a 650 AVS on a stock 340 I had to jet it up a lot and put on a bigger accelerator pump nozzle to get rid of the bog:

http://store.summitracing.com/partdetail...mp;autoview=sku

i did all the mentioned above and had the same problem with my eddy thunder AVS and the TQ i switched to later. only thing that cured that off idle hseitation was goind from a mechanical to an electrical fuel pump. that caused other problems, but the hesitation went away ...