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I am building up a 402 for my 70 Chevelle SS. I have the original engine in it now but I'm afraid to push it too far and maybe blow it up. That would drop the value of the car a bunch. So I'm putting in another 402 that I picked up. What I have is a set of 3981063 heads. Are these any good for a street perfromance engine? Also what is the difference between a cast, nodular iron and a steel crank? This block has a nodular iron crank in it now.

A cast iron crank is not as strong as a steel crank. But cast cranks are more forgiving about balance and vibration problems. A steel crank will take more rpm/horsepower abuse. Most 402 two bolt motors are cast iron cranks. To tell the difference, look at the front of the crank from the main journal to the rod journal down the center of the arm will be a line that sticks up. If the line is only 1/16"-1/8" the crank is iron. If the line is 3/8"-1/2" and looks like someone took a grinder across it. It is steel.

Cap61, the cast crank is plenty strong enough for normal high performance use, the can take a lot of punishment. I have a few friends who regularly drag race cars with cast cranks, and have no problems at all. The 063 heads are a great head for a street performance car, they're small oval port, closed chamber heads. About 101cc chambers, should have pretty good compression ratio with those heads. They flow great with the stock valves even. Use them!!!

The pistons that are in it are definetly not flat. I have a GM part number of 3968875 and the pop up portion just about fills the combustion chamber. Anyone jnow where I can look up that number? Also it has the stock bore of a 402. I think it's 4.125 and it came with the nodular iron crank. I bought it from a guy for 500 bucks. I think I got a dam good deal! What compression ratio would that give me?

Thanks for the input guys.

Higher compression ratios were common back then, when we could still get good gas....I'll bet you're at about 11.1 or so...hard to say without knowing the volume for sure, but I'll bet that's not far off. That was a super deal for the money!! Good job!!