Type of carb to use

[nomadci]

My newly installed 409/340hp has the stock Rochester carb (rebuilt not jetted) on it and runs pretty strong. I was wondering if I could get more performance from a Holley 670-750cfm carb? It seems Holley's don't produce as much torque (articles on Holley's) as the stock Rochester, but may produce more horsepower. I am trying to keep the motor as stock 'looking' as possible (air breather will cover most of carb) while trying to get some good performance. I have a mild cam(.528/268I, .526/275E), roller rockers, dbl roller timing chain, stock exhaust manifold, 2500-3000rpm torque converter, stock 340hp block& heads, 370 posi rear end and stock suspension. Using the formula CFM=(RPMXCID)/3456, with 4000rpm's cruise speed puts me around 670CFM (375 primary).

 

[Mr.Jimmy]

Call up holley and talk to them about there HP series. I have a couple of them and I am VERY happy with them on the dyno. The number made it a simple choice for me.

 

[models916]

What kind of manifold are we talking here?

If it has the chevy supplied pattern you would need an adapter to mount the Holley. We have used the new Avenger Holley in varying CFMs on lots of motors we put on the Dyno (no W motors by the way) and have found them to be tuned right on the money right out of the box. Holley did their homework on the metering and jetting on this series. Might want to ask about them.