I have a Clinton horizontal shaft engine I took apart as a kid and never reassembled. This was stored in my father's garage that I recently cleaned out. I have all of the parts, just never got around to rebuilding it. My question is...what did this come off of? It is vented at the top of the flywheel cover. It has no vent in front of the flywheel. It's an interesting design. I haven't seen one like it. Any experts here have any ideas or an answer? Judging by the size of the piston, I would guess it to be 3 or 4 HP. I didn't get the numbers off the motor. I can if need be. Thanks for the help!