Where do I start?
600 cfm will cover 400 cubes on the street, but not the strip. The higher you rev the engine the more cfm you will need to cover it.
This is where I get prople mad at me. The 396 is only good for scrap metal. The SBC 400 cube motor will run rings around it for half the price. The BBC was designed to be a HIGH compression race car engine that would run all day long (12 hours to 24 hours) at 7,800 RPM. You can not run high compression with today's gas-ohol. Because of this you need a BIG big block. 500 cubes is a good start.
Rectangular port heads require 500 cubes or more displacement to begin to make power across the engine RPM range. They are duds on the street and a set of "Peanut Port" truck heads will out perform them on the street because they are the same size as a SBC 400's heads (190 to 220 cc in volume depending upon year made). To get any power out of a 375 horse 396 (it was rated at 425 horse only in 1965 at a higher RPM than the 375 horse was from 1966-70 because Chevrolet's marketing people wanted to sell the idea of a 396 replacing the venerable 425 horse 409) you have to spin it to it's red line and hold it there while you turned left.
The 375 horse 396 came with 320 cc rectangular port heads and a radical for the day mechanical (solid) flat tappet cam with a high rise manifold and a 780 cfm Holley carb. It had pop up pistons with 11.0:1 static compression and closed 90 cc combustion chambers. If you were to recreate that motor you would have to run it on 100 plus octane race gas; it would not run on today's gasohol. It was replaced a year later by the 427 that made 425 horse at the same low (compared to it's racing potential) RPM.
A 396 has bores that are so small that it has to have notches cut into the deck to clear the valves. It is the equivalent of putting money into a 305 when a 350 was available for the same money. Both the 305 and the 396 are small bore engines that were designed not for racing but for use as a truck engine. It was ultimately produced as a 366 not a 396 in a truck block for medium duty trucks and school buses. The smaller bore 366 makes torque with a long stroke small bore. The 396 has a half inch longer stroke than the legendary 409 did (which was a big bore short stroke race car engine to race at Dayton's high bank track). No one has written a song about the 396.
Now back to the 500 cube motor. For the same money you have in your 396 you could have built a 496 (the 383 equivalent of a 350 rebuild). You would have started with a 454 donor motor out of a light truck (not the tall deck medium duty 454 truck engine). Add an even longer stroke crank, eight thirty over pistons, and you are close to the 500 cubes those rectangular port heads need to run at the RPMs encountered on the street. With open chambered (121 cc combustion chamber), and the smaller 230 cc oval port heads found on the 350 horse 396 and you could make 500 to 600 horse on your pump gas street driven motor.
Your cam and head choice prevents your car from having any pep, aggravated by your small bore. A modern BBC can make up to 1.2 horse per cube. Only way to make power with a BBC is to go big; but in every case, it is the combination of parts that you choose that is important.
Crane Energizer 282 H08 Flat Tappet Hydraulic 2,200-5,600 RPM operating range with degrees of duration at 0.050" 226°, valve lift 0.533", 108° LSA, auto trans requires 2,500+ converter, 3,000-3,400 cruise RPM, 9.5 to 11.0 compression ratio advised. This cam needs a notch ground into the rear journal of the cam to run with your 1965 block. Without that notch you will not get oil to the top of the motor burning up the rocker arms and push rods and destroying the valve guides and valves.
Last edited by Big Dave; 02-11-2018 at 05:46 AM.