Old 08-30-2007, 06:44 AM
  #4  
mcracecars
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Join Date: Dec 2006
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just to add here....
boost is nothing more than the measure of pressure built up in the intake.

most companies that sell street blower kits that go onto mildly modified motors set them up to underdrive them (top pully larger than bottom) maybe 10 to 15 % underdriven, this gives anywere from 5 to 8 lbs of boost, depending on engine. Which is usually pleanty for a performance street car/showcar/ occasional track car, and is usually all a stock style or mildly moldified motor can handle.

since the whole idea of any race/performance motor is to get as much air into and out of the motor as quickly and as efficently as possible, supercharged motors really work better with as little restriction as possible.
throw away all the ideas of head ports and intake runners, and header primaries all selected to build mid range and low end tork.
supercharged motors love "big" big ports, big headers, big cid, big cams. But of course these things still have to be sized accordingly.

if you have a mild small block lets say, with a 6-71 kit builds 8 lbs of boost, later you put a big block, with good heads, cam , now you only see 4 lbls of boost, this means that the big block is more efficent at getting the air through the motor and does not have as much pressure in the intake.
or say you go from a 6-71 to 8-71, on the same motor, same percent of drive, you will see a gain of boost.
you cannot go wrong asking bds for advice,(there are others too) they got a catalog with charts and things to help you along.
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