It'll probably be next week before I get the chance to take the amp apart, so don't hold your breath.

Nah Spaw it was a V8, I don't even remember the size, smallish I think. But you're right about it running when it should have been worn out. The compression was low when I bought it but it was priced right at $900. I figured I'd have to rework the engine after a year or so. But it was still going strong after eight or nine years of mostly gravel roads. I finally sold it for $200 so it cost me less than $100 a year. The biggest repair job was a new half shaft which cost around $100 including labor.