They are durable and noisy, no water jackets to quiet them.

Thats Deutz. Good engines, popular for construction machinery like pavers, where they get started in the morning and ignored all day. Go easy on the ether, too much will stretch the cylinder bolts, then you have to reset the bolts in that head (not hard to do). Generally an easy engine to work on if you do your own mechanic work.
Bill

They are very noisy and vibrate, but are cheap on fuel and tough.
We have a miller Airpak with over 8000 hrs, and have only had to
work on the compressor.