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| Pontiac - Boost Turbo, supercharged, Nitrous, EFI & other Power Adders discussed here. |
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#21
04-30-2010, 09:40 PM
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Sounds like a good combo for E85 or Methanol 69Goat
 At 8.5:1 and 20% OD my old gas combo was quite the furnace - can't imagine 10.25:1 would be too friendly...
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The secret to happiness is not getting what you want but rather, wanting what you have. |
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#22
05-03-2010, 05:59 PM
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Yeah when I get more stuff nailed down I'll definitely post back more. I know I'm going to use my 4X heads for this blower build up since I have them and it will put my compression in the right area.
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1999 Trans Am Ws6 Slp Lid, K&N, Smooth Bellows, Ls6 intake, Spec Clutch, Spec Alum. Flywheel, Spintech Cat back. 1970 Firebird Esprit 455 Pro Street project |
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#23
05-04-2010, 01:10 AM
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What are the advantages or disadvantages of using a 6-71 or an 8-71? They use the same manifold and drive setups right?
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1999 Trans Am Ws6 Slp Lid, K&N, Smooth Bellows, Ls6 intake, Spec Clutch, Spec Alum. Flywheel, Spintech Cat back. 1970 Firebird Esprit 455 Pro Street project |
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#24
05-04-2010, 03:03 AM
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The 8-71 is capable of moving more volume per turn, and therefore will be more efficient on an engine that can use that volume than a 6-71 would be. Thats not to say the 6-71 isnt a perfect size for many applications.
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#25
05-04-2010, 10:20 AM
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A 6-71 moves about 400ci of air per turn versus an 8-71 at 436ci. With few exceptions blowers gain 1 inch of case length on the back of the blower when increasing size: 6-71, 8-71, 10-71, 12-71, etc. Given a standard discharge (no offset) for a street/strip application they will then utilize the same front snout length and associated drive hardware. Choices of pulley pitch (1/2", 8mm, 14mm), as well as belt style (rubber, kevlar, etc) is based on expected drive ratio of the blower. 8mm pulleys and a rubber belt will work to a bit over 30% blower OD in most situations - that's a bunch.
On our Pontiacs the biggest blower you can run and still locate a distributor in the standard location is an 8-71 - and you'll need a single point housing or other non-HEI similarly sized cap. For a 400ci I might consider a 6-71 in a street app. for the right price, but for a 455ci or larger I wouldn't run smaller than an 8-71.
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The secret to happiness is not getting what you want but rather, wanting what you have. |
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#26
05-04-2010, 04:40 PM
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400 cubes per rotation?..and the engine turns over 2x for a complete cycle..so ya got 800 cubes of air going in to a 455..or 872 cubes with the 8-71..less than 10 percent increase..(9% by your figures)...will you feel it on the street?..only if the engine will accept and use the air in the rpm range you are running..the tires were on fire when ya hit the throttle anyway..not trying to dissuade you metal, just some fun facts..
street blowers aint racing blowers..be real with your needs..either blower will make your day on a street car, truly that.. 
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