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Old 02-19-2013, 06:59 PM
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blower boost

I am running only 5lbs of boost on bbc. I am not seeing 3-5 lbs until i get around 6000rpms. Anyone running this low of boost and should i be getting into my boost sooner. This is a drag car only. I have a 8-71 on a 427bbc with 61 top and 49 bottom pulley it should be around 20% underdriven. (8mm) . I have my 1/8" line coming from back of intake then it splits between my btm and autometer gauge. I checked hauge seems to be working fine. I feel a lot more power when i take off . I went from a 1.78 60ft to 1.66 60ft.when i installed blower.
Dart iron eagles 345cc
Solid roller cam 710/715 lift
2x850 holleys
Thxs
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Old 02-19-2013, 09:04 PM
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Per BDS website, a BDS stage 1 blower running 20% under on a 427 will give 4lbs of boost. Boost is measured at 6000 RPM. Seems about right if this is what you have. Tell more about your engine specs - compression, cam specs, exhaust. When does the boost start? It should be quite instant.
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Old 02-19-2013, 09:38 PM
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Compression is 8.75
Cam is .710/.715 lift 3200-7000 solid roller @112 lobe
I shift around 6200. So as soon i see boost at 6k i have to shift pretty soon. Just dont seem rite.
Th400 with hughes 3800 stall made for my specs.
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Old 02-19-2013, 09:47 PM
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Blower wont make boost until it is under load. With a 3800 stall, boost would be starting around there and build up to your max amount for the pulleys you have at 6000. Boost should always be measured at the highest RPM - and really no need to go much over 6000 with a roots blower. They make great torque low and mid range. If your cam range starts at 3200, I would get a tighter converter - like around 3000. Boost would come in sooner. The torque created by a roots blower would pull hard and put you in the power range real fast and you would be seeing boost much sooner.
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Old 02-19-2013, 10:39 PM
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why not raise the boost to 6# and pick up 60HP plus it should boost for a longer time
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Old 02-19-2013, 10:50 PM
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if its a drag only car why not raise the boost to around 15 lbs, and have some fun
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Old 02-19-2013, 11:19 PM
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Sounds good 15lbs go big or go home ..
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Old 02-20-2013, 11:58 AM
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Quote:
Originally Posted by menoaz View Post
Sounds good 15lbs go big or go home ..
Get some high octane gas for 15 #s boost. 110+
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Old 02-20-2013, 02:11 PM
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Quote:
Originally Posted by menoaz View Post
I am running only 5lbs of boost on bbc. ...
Solid roller cam 710/715 lift ...
Is that the cam recommended by the blower company?
How much boost is the engine built to handle?
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Old 02-20-2013, 02:49 PM
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if you only want to rev it up to 6000rpm the cam is probabily all wrong for this motor. too much duration.
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Old 02-20-2013, 04:01 PM
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Thxs guys for all replys. Getting back to the original question it sounds like the gauge is measuring it correctly under a load only.
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Old 02-21-2013, 06:22 PM
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That large cam possibly is bleeding off your boost in the overlap. Letting it go out the exhaust. If you start small and build up you get there everytime.

I have been doing some projects placing blower and turbo systems on stock vehicles and getting unbelieveable results with 4-6 psi. You would not believe a 1.9L saturn twin cam 5 speed with 5psi. A eaton compressor made to be a blow through system on a 3.1L gm fwd is a rush. A shot in the arm like no other. No heavy fabrication of brackets, no oil lines for eatons and no turbo oil system compromise. You use a $25 oil filter sandwhich for the turbo feed and drain. Kits are everywhere for $500-600 . A blue tooth OBD connector talks to your smart phone for live data. Still it eludes me how easy it is. I remember the winter long cam + head engine rebuilds of my 20's . Now it is bolt on and done in a weekend.

If it was 20 years ago and this equipment had this avalibility, it would have replaced baseball as the nations past time. Im starting to like? OBD..did i admitt that?
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