Pulling my engine to be sent to the machine shop to be built. Turning the worn out 302 into a peppy 306 with a mild street cam. Goal is around 300hp and just as much torque. For now the stock heads will be ported and polished, maybe in the future I will go to a better flowing head. My big question is about carburetor and intake. Starting with the carb... How do I figure how many CFM the carb should be? Second question is for the intake. Single or dual plane? What is the difference?

 

In a dual plane manifold the flow is divided. Two cylinders on one bank and two cylinders on the other bank are fed by half the carb. In a single plane manifold, there is a plenum chamber under the carb and all eight cylinders feed from the plenum.
Dual plane offers more driveability and bottom end. single plane better for top end.
Carb size, a lot of variables. Cam, compression, rear gearing, compression, max RPM, all affect the carb size. For a starting point I would go with 600cfm and vacuum secondaries.
Here are the two manifolds, first is the dual plane.

 

I suggest referring to a carb sizing calculator: http://www.summitracing.com/expertad...cfm-calculator

A street small block would range from 500 to 650 cfm. Assume 85 percent volumetric efficiency.

In terms of intakes, a single-plane is for high RPM use. On the street (and a heavy truck), torque is the name of the game so stick with a dual plane.

Many choices out there.

 

Thanks for the input guys. I was looking at a Weiand intake and 625 CFM Demon 4bbl. So I should be on the right track.