x 3
I had to buy the biggest star vac pump they make to accomodate a 632 bbc mine was set at 11. There is a big difference when your running at idle approx 1500-1900 rpm to when your on the top end of the track, wide open pulling 7500 to 8500 rpm.
And for the small cost of a check valve, I would certainly recommend it.
Don't get me wrong, In sincerely hope you have came up with an idea that is not only mechanically effective, but cost effective as well,
Good luck and keep us posted with your results.