Bob

I think the Offy had a one piece cast iron cylinder and head assembly (Head gaskets weren't too good back then), then they would sandwich that big piece of cast iron between an aluminum crankcase and bolt on aluminum cam towers combined with big aluminum side covers for the water jackets to make the it look like an aluminum engine. The valve stem on the exhaust valve on a lot of them were 1/2" and were drilled and filled with sodium to aid cooling.

Boreing and sleaving and valve jobs were a pain in the neck requiring special tools. Won't see any Serdi cut seats on an Offy. The old Crosley was actually a low buck knock off of that old Offy.

My dad owned an automotive machine shop that did a lot of performance work back years ago,and I can still hear him cussing both those engines. My favorite Offy was the 270 cid it's nick name was "the widow maker" I think it was outlawed because it was just plain "Bad A$$" back then.

Honest Dad himself