[justa6]

Although your right about the rings I believe your incorrect that they are the only advantage.

The guy that did the machine work on my motor had done a lot of Busch, IMSA, etc motors and he told me that they've spent a lot of dyno time confirming the usefulness of pulling a vacuum in the crankcase. One of the big advantages is that instead of the pistons working against ambiant air pressure on the downstroke they are not "pushing" against anything. True that the rings seal better but you don't have the pumping loss.

Japanese motorcycles gain some power by having "equalizing" holes between each cylinder (below the rings at BDC) so that instead of pushing against crankcase pressure they have the air relieved below the piston by the upstroke on the next door cylinder. So I agree that power will definitly increase with a vacuum in the crankcase. As you know I'm going to use my dry sump pump to do it in my motor and will call the number of the guy you gave me for the vacuum break as I think that is also a great idea.

Regards and thanks again,