wrote:

Jimmy 371 - supercharged but not likely turboed.

Actually the Jimmy 371 is a naturally aspirated engine. The piston
covers the intake opening in the cylinder wall before the exhaust valves
close. The Rootes Blower is there to improve exhaust scavenging not for
supercharging. The GMC 2 stroke cycle diesels generally are not
supercharged even though they have a Rootes Blower. If they also have a
Turbo then they are supped. I've probably missed something here. My
experience is with working on GM 2 stroke cycle diesels in power boats.

Gary Thomas