I did not build this, the previous owner did, and this engine is a monster, but puurrs so smoothly, you could put a marble on the top of the flame arrester and it won't go anywhere. Bored .30 over, 9.5 to 1, cast alum pistons, 650 carb with edelbrock high volume manifold, and glenwood logs. ALso has a light flywheel with MSD ignition. I am guessing at least 300 HP.