Which Carurator size?

...Did you say 315 Degrees Duration!? Sounds like a 'race only' cam and not great on the street. It would be very low on the vacuum. Just My opinion. I'am running 292 Duration with a .560" Lift and it is Right at the limit, just where I wanted it, with a very slight hint of a 'Lope'. Vacuum is 7-9 In. HG. But the throttle response is Excellent! I have the closed chamber heads with flat-top pistons; right at 10.5 to 1. The carb is a Holley 750, Vac. Secs. on a torker manifold with a 1 inch open spacer. I would NOT go any bigger on the carb. Many would tell us that a 650 cfm would run more responsive, and get better MPG's. Run Machanical secs. for ultimate control of secondary opening if you don't mind burning more gas in trade for faster 'come-on of power! But Expect a Bog if you choose to Big of a Carburetor. Stay tuned at the 'Photo Gallery', for my next installment of Photos of My custom machined, 'One of a Kind' Dual Quad High-Rise Manifold. It's a 'Highly Modified' Weiand Tunnel Ram, with the Top adaptor removed and the Carbs lowered 2.5 Inches on custom machined plates. My measurements tell Me that this system will 'Just' clear (1/8" to 1/4") the rear deck lid. I will be installing it in 1 to 2 weeks. Purely Experimental, But isn't everything WE do to these Beautiful Machines, Experimental!?...

Day in, day out, for most performance applications a 750 Holley is the right carb for the Cleveland, from mild to wild. Demon carbs are flowed wet & the numbers tend to run about 100cfm lower for an equivalent carb.

Vacuum secondary or double pumper matters not, what you need is the carb set up for your engine. If you buy a new Holley, it will still not run well out of the box.

George

I'm running a Holly 750 DP with 72 primary and 80 seceondary jets with a 286 duration .560 lift
It runs great !