We’ve got the answers—the Summit Racing tech department tackles your automotive-related conundrums. This week, we’re helping to rebuild a 6,500 rpm Chevrolet small block 350.
R.B. • Las Vegas, NV
Q: I am building a Chevy 350 using a four-bolt main block, a 400 crank, and 5.7-inch rods. The crank has knife-edged counterweights with lightening holes, the rods are polished and weight-matched to within a 1/4 gram, and the block is deburred. I have camel back cylinder heads with ported and polished combustion chambers, 2.02/1.60-inch valves, and Harland Sharp roller rockers. The heads are also port-matched to a Weiand X-CELerator intake. I also have a Summit #K1104 cam (224-degree duration at .050 inches.465-inch lift), a Pete Jackson gear drive, a Carter 750 cfm AFB carburetor with a manual choke, and an HEI distributor with an MSD 6A ignition. I regularly run my engines up to 6,500 rpm.
I have not purchased the rebuild kit yet, and I need some advice before I decide what kit to buy:
- What compression ratio should I run? What type of piston should I use? I run 92 octane gasoline and 108+ octane booster
- Should I swap the Summit cam for a hydraulic roller cam? What duration and lift do you recommend? I have a 2,500 rpm stall converter and want a dual pattern cam that will match the converter
- Should I paint the inside of the block with ceramic paint? Is it worth the cost to have the tops of the pistons and combustion chambers coated?
A: We’ll try to answer the questions in the order they were asked.
First, we’d recommend KB hypereutectic pistons: KB135. These particular pistons have a 18cc D-shaped dish that will give you 9.7 to 9.5:1 compression with your camel back heads. Second, we’d definitely go with the hydraulic roller camshaft. It will give you more lift at the same duration, less friction, and no break-in problems. Try Crane part number 119831. It’s a dual pattern cam with 222/230 duration at .050 inches and .509/.522 inches of lift with a 1.5-ratio rocker arm.
Since you have deburred the block, we’d recommend that you paint the intake valley with ceramic paint to aid oil drainback. As for heat-coating the pistons and the combustion chambers, it will help keep more heat in the cylinders, which improves combustion and increases power. For an engine like yours, the coatings would probably be worth the cost.