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B&M 250 Supercharger HP guess

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Old 01-29-2012, 08:50 PM
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Default B&M 250 Supercharger HP guess

Hi Everyone i am not a boat owner yet but i do have a 454BBC with a BM250 supercharger ....oval port iron heads , cam of unknown spec but rumps a little timing 21 degrees locked , Hooker pro comp 2 inch primary headers running 8.5-9 psi with E 85 Fuel ......in a 83 GMC pickup truck it runs great with one quick fuel 1050 carb jetted up ....SO Anyone want to take a HP at the crank ...experience.... guess , i know a lot of guys are running this Blower on here ..

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Old 01-29-2012, 08:51 PM
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Old 01-29-2012, 09:17 PM
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I will answerbyour question with a question- have you run the truck on the drag strip? If yes, then E.T., trap speed, and final drive ratio should get you a pretty close guess.

Blind folded guesstimate would be 450-550hp.

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Old 01-29-2012, 09:57 PM
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Rick its got 39 inch tires on it and a 9 inch lift and we have no strip where i am so strip testing is prob not going to happen , with 5.13s it spins hard .....ill prob dyno it one day i was told a 30% loss with the driveline it has tire weight 400 etc ......the butt Dyno feels good though
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Old 01-29-2012, 10:19 PM
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im going to say not much with 21 deg total timing,thats way to low.you did not say what the compression ratio is,so im going to assume its 9 to 1 or less.you should be locked at 34 deg,also,no cam specs,but il guess it should make 550,maybe 575,if you get that timing where it needs to be.i guarentee you,it will wake that motor up.do the headers get cherry red near the exhaust ports,the egt,s have to be sky high with 21 total timing.
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Old 01-29-2012, 11:42 PM
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Mike i was just looking at the timing spec by Weiand they are saying 28-34 , so you think i can lock it at 34 w/o start up or general driveablity issues.... i set it at 21 thinking less timing would prevent problems ( im still trying to escape my Buick Granad national tunning ideas where 34 degress would be really bad 26 deg was a race set timming )....the dist does not have mechanical advance and the vacume is not hooked up or working when hooked up , i think it may have been out of EFI car that had computer controled ignition possibly why the mechanical advance is not there . The Comp ratio is unkown the this was a low budget neanderthal racing project the long block was never taken down and as is when i got the truck , i added the blower and fuel etc to it . Ive never noticed the headers red ive been driving it like that since last May ......im going to bump it and try it . i appreciate the advice that anyone has to offer . This is my First BBC and Roots blower project
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Old 01-29-2012, 11:49 PM
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http://youtu.be/MRfEBauB04Q
video of motor running

Last edited by galoush; 01-29-2012 at 11:54 PM.
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Old 01-30-2012, 12:15 AM
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Mike the only a reason the headers may not be getting red is the E85 Fuel .....the AF ratio is good on the meter im gonna bump it up and see
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Old 01-30-2012, 06:06 AM
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Default 250 b&m

We made 785 hp @ 5800 with a 250 ( intercooled ) @ 5 psi ( 7psi before the chiller ) 489 with 731 crane hyd roller . 9 to 1 static compression .
Your total timing is way to low ... I would run no less than 30 degrees depending on fuel used . We run 93 and saw the egt's shoot up @ 28 degrees ... engs were much happier @ 30 total.
B&M had a 174 blower they advertised bolt on 100 hp @ 5 psi back in the day . As already stated ... run your truck and get a ET ... that will get you a ballpark HP .
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Old 01-30-2012, 09:23 AM
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Quote:
Originally Posted by galoush View Post
Mike the only a reason the headers may not be getting red is the E85 Fuel .....the AF ratio is good on the meter im gonna bump it up and see
e85 has a higher octane rating than 93 gas,all the more reason to add some timing.-
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