Slow 350!! Help

Heres the scoop.

I have a chevy 350, with HEI ingnition, bored .030 over, and a mild cam. The motor runs good, idles well, a fresh rebuild in '03. My main problem I'm having now is she'll wind up, good and strong till about 3600 rpm in 1st, then she will stop pulling, and level off for the most part. I have disconnected the vacum advance because I was getting spark knock at low rpm, I've tried to retard the timing, but even 1 degree and it feels less powerful. anymore and it will spark knock, currently it's at +4 degrees...(on the balancer)... I'm running the 89 gas, which runs good. and a Rodchestrer carb, I think it's a 750cfm, but I'm not sure.

I just don't know what to do with it, is it my vac. adv.? timing? or Overcarburation????

Any help would be greatly apprecated!

You didnt mention if it just started doing this or did you have problems every since the rebuild? also what compression are you running? is the engine running hot? is the mixture lean? all can lead to spark knock problems.

Was the carb rebuilt at the same time?

A slow 350 chebbie??? Sounds like situation normal to me!!! Tee Hee Hee