I've owned three M21s. All had iron heads. At least two should have been alloy..... Back then we didn't have torque wrenches much and we didn't have solid copper gaskets.

Slightly off topic, but you see so many badly damaged iron heads with multiple fins missing. These are bloody heavy, tough lumps of hard metal. It makes one wonder just how cruel & downright brutally careless were some of the past owners of these machines?

I expect a lot of the damage is done by removing head bolts and spark plugs with the wrong spanners. Ron

email (option): ronpier@talk21.com

On my present one what hasn't broken has simply rusted away.