Which yields more horsepower?

[ERA Chas]

I agree with John, you need velocity, not more cfm, especially with your small cam and heads. Your 670 is fine and feels sharper with the dual plane.
Yes the B303 is from FMS.

[Sledge]

Skip:

for what it is worth

I have car 168 with the standard CA Cobra 351W setup for that time frame.

When I went to the dyno I mentioned to the dyno guy that I had the 770 CFM carb and that pretty much everyone was telling me that it was too big. He said not necessarily so, let's give it a try.

The dyno runs, once the car was checked for proper jets, with air cleaner on, and leaking and poorly-matched slip-fit headers and sidepipes, still gave me 320+ RWHP @ 6200 rpm and 330+ lb-ft RW torque @ 3000 rpm. Both curves were pretty smooth from 1500 rpm on up. We took it all the way to 6800 rpm on one run but there wasn't any real payoff.

The car idles fine at about 1000 rpm but it spits a little until about 2500 rpm at partial throttle, then it really takes off. Overall I'm happy but I sometimes wonder if I'd find nirvana with a slightly smaller carb.

The dyno guy said he didn't see much point in going to a smaller carb.

When I find myself with some of that pesky excess income I may try a slightly smaller carb. In the meantime I am (perhaps ignorantly so) reasonably happy.

Cheers