Let's clear some of the cigar smoke from this thread.... Have a read of Weiand's manual that comes with the 144 blower. I'm running 10lbs. of boost with this blower. To do so means $$$$ spent on the engine build, cooling system, ignition system, drivetrain, exhaust system, frame support, rear end, ect. Going this route is not to be taken lightly if you want equipment to last. Don't guess on this build. I've posted many threads on my initial set-up and upgrades I've done. PM me if you are serious on going the 144 blower route.
One other thing ....Comparing a roots blower to a centrifical force blower or a turbo is like comparing apples to oranges...This is also covered in the manual.
Here's the link...http://www.holley.com/data/Products/Technical/199R10244-1.pdf
In it they state to prevent detonation to have a 8.5:1 comp. ratio.
LARRY