250 HP
Oldsmobile 455ci V8's have between 310-390 HP depending on the exact year and maybe other factors - I have one in my '72 jet boat, when in this application some HP is taken away when total HP is caculated because of the way it is used. Adultoys2007@gmail.com
From my recollection, they had 5-bladed fans attached to heavy-duty fluid fan clutches that were controlled by both rpm and temperature. If you have an overheating issue, I would first suspect the fan-clutch.