Has anyone ever heard the term pinning the mains? I believe Smoky Unick refers to this in one of his books. How is it done? I guess it helps lock the main caps in so they don't pinch the bearings under extreme loads.

You machine holes in the block and cap and insert dowel pins that hold the bearing shells via holes you drill in them. Some only had a pin in the cap. I think this evolved from the flathead days. A downside is that it reduces (slightly) the bearing surface, plus you're dinking with the finish of the bearing. I seem to remember that some aluminum rods I've used in the past also had pins.

Dave,
I think what Bob is referring to is pinning the main caps to keep them from moving around. Pontiacs are like that from the factory. You drill throught the main cap out at the edge and put a pin into the block. Don't know if it is really worth it or not. Most Chevy engines just do not have main bearing problems until you get way up in the horsepower/rpm equation. Then its time for an aftermarket block anyway. A lot of stuff you read in older books was done due to the fact that they did not have the parts available that we do now.