Originally Posted by
dieselpilot
The OPS was a 1.20 size. It's hard to find any info and the engines are rare. HB are bevel gear driven. I have a few and have had one apart.
On the louvered gate valve you'll want to check what the flow coefficient of that might be. Doesn't sound good to me.
I love big four strokes (especialy the sound). I hope to see one of those big OPS four strokes turning a big prop some day. The OPS .90 I refered to was a watercooled 2 stroke inboard boat engine. It was a beast, and looked the part due to the big square jug. I understand they still make them.
I just remembered that the HB valve drive shaft (and the tube it runs in) is in the rear of the engine (not the front like I said earlier), and the carb is in the front (aimed downward at an odd angle). The HB was also available in a .25 car version, with big vertical fins on the head. Never saw one of those in person.
I agree about the louvered gate valve. So many port edges mean a lot of turbulance. High speed airflow will be lousey I'm afraid.