Don't some "street" (1:1 scale) blowers still use straight lobed rotors? Hampton's I think, and the small B&M's? Anyway, about the clearance, do you think the rotors are gonna get warm, and expand? That would take up some of it, and give a nice precise fit. But the case is gonna expand too... With the alcohol fuel flowing through it it probably won't get very warm though...Hmm, just thinking out loud here...If that sucker is spinnin' at 1/2 crank speed, that should be, what, up to around 15,000 R.P.M.? You oughta get SOMETHING commin' out as far as boost is concerned, aye??? Well, some volume anyway, but boost, who knows? Leakage and cavitation might be a problem...Hope it works man!!! My 27 1/2 cts. (inflation)