I have fooled with them, and I can do a boost ref carb, but that cost thing gets in my way too. Would love to own one, you can't beat the sound of a blower motor doing a burn out. One of these days I'll have one.
I have a blower, but no car to mount it to. It's a 8V71 blower that I got it for $100 off of ebay which seems to be a good price. There is a guy on ebay making an adapter plate to put the 8V71 blower onto a 6-71 intake. I've thought about putting it on one of my engines for a future built. I have a 302 sitting here, but no car to put it into. For a possible "cheaper" blower build, it might be something to look into.
8.1 is the approximate compression for a blower motor although i've seen higher compressions used on the more modern engines using the centrifical blowers. Alot depends on the overdrive, comperession etc.. A street motor should be underdriven and a race motor overdriven for best performance. As far as O-ringing, a street motor can use good head gaskets and a race motor should use O-rings.
If you want Good info, go to Hampton Blowers website or call Don Hampton and he will gladly talk to you about what works and what you need. He has been doing it since the late 50s,built the original Magnesium Blower and has built race blowers for Garlits, Prudhome and all the big hitters in drag racing. He's 79 years old and gits it done everyday!
Thank you Mexican Bob! I gotta agree with Mario, real good info with some honest background. I mean Don Hampton would sure as hell know, he IS a supercharger! And I had forgot all about him till you brought him back, thanks.
Prior to his move to Hawaii, Gale at Plumb Crazy Blowers was our local BDS blower rep, and very knowledgeable on blower tuning. He also owned a Austin like mine with a little 4-71 blown Buick V6 in it, and was always trying to get me to put a blower on my SBC in the Austin. He did say that 8:1 or 8.5:1 was a good place to start, but said he could easily make my higher compression work great with the right pulleys.