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Re: Are there any "small" OEM BB crank pullies? [Re: BradH] #2722365
12/07/19 06:26 PM
12/07/19 06:26 PM
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AndyF Offline
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Here is a March dual groove pulley. This one is about 5 inches in diameter. I'm underdriving the water pump a little bit but over driving the alternator. The PS pump will also be underdriven.

DSC_4040 (Large).JPG
Re: Are there any "small" OEM BB crank pullies? [Re: AndyF] #2722378
12/07/19 06:49 PM
12/07/19 06:49 PM
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Mt Morris Michigan
mopar dave Offline
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Is my water pump seriously over driven with 4.5 wp and 5.5 crank pulleys or just right for street/strip? Do you think its eating up an excessive amount of power?

Re: Are there any "small" OEM BB crank pullies? [Re: BSB67] #2722516
12/08/19 12:29 PM
12/08/19 12:29 PM
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BradH Offline OP
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Originally Posted by BSB67
Originally Posted by BradH


Not sure what diameter the Moroso is, only that it says a 30% reduction in pulley speed, IIRC. My brain hasn't shifted into calculator mode to reverse-engineer the diameter.
.


Reduction will be directly proportional to diameter.

Diameter? 70% of 6.25 is only about 4.3... unless the standard factory pulley is actually 7+".

Last edited by BradH; 12/08/19 03:04 PM.
Re: Are there any "small" OEM BB crank pullies? [Re: AndyF] #2722518
12/08/19 12:34 PM
12/08/19 12:34 PM
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Originally Posted by AndyF
At 3500 rpm cruise you could use a smaller pulley without any trouble. My guess is that the factory designed the water pump to be really effective in the 2000 to 2500 rpm range so you are probably overdriving your pump a little right now. A smaller crank pulley might improve cooling on your setup.

I was thinking pretty much the same standard RPM range; 30% slower than 3500 is 2450...

Re: Are there any "small" OEM BB crank pullies? [Re: BradH] #2722534
12/08/19 01:00 PM
12/08/19 01:00 PM
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Oakville, Wa
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67 Barracuda, 470" B, Glide, FuelTech FT600, Precision, Ptc, QA1, Calvert, Smith racecraft, Afco, Dana 60. 275 radials
Re: Are there any "small" OEM BB crank pullies? [Re: HOTMOPR] #2722560
12/08/19 02:39 PM
12/08/19 02:39 PM
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Originally Posted by HOTMOPR


That is the Doty pulley.

Re: Are there any "small" OEM BB crank pullies? [Re: BradH] #2722565
12/08/19 03:06 PM
12/08/19 03:06 PM
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Prospect, PA
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Originally Posted by BradH
Originally Posted by BSB67
Originally Posted by BradH


Not sure what diameter the Moroso is, only that it says a 30% reduction in pulley speed, IIRC. My brain hasn't shifted into calculator mode to reverse-engineer the diameter.
.


Reduction will be directly proportional to diameter.

Circumference, not diameter. 70% of 6.25 is only about 4.3...


And 70% of circumference still results in 4.3" diameter. Pulley speed, circumference and diameter are all proportional.

So either Moroso made an error, or their pulley is 4.3, or they started with a different pulley diameter for the claimed 70%. FWIW, the crank pulleys I have here range from 6.5 to 7.25.

Re: Are there any "small" OEM BB crank pullies? [Re: BSB67] #2722570
12/08/19 03:33 PM
12/08/19 03:33 PM
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BradH Offline OP
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I must have been editing my original comment at the same time you were posting your response above. I think we're actually on the same page now.

Re: Are there any "small" OEM BB crank pullies? [Re: BradH] #2722586
12/08/19 05:18 PM
12/08/19 05:18 PM
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Prospect, PA
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I kinda figured that you probably knew. I know that I've raced to real stuff back in.

Re: Are there any "small" OEM BB crank pullies? [Re: AndyF] #2722589
12/08/19 05:35 PM
12/08/19 05:35 PM
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montana
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Years ago, MP used to sell March pulley sets. When they quit, they were selling them off cheap. I picked up a few different sets with that smaller lower pulley and have used it on a couple of street cars. They are quality pieces.


64 Dodge Coronet 440. In progress
1998. Dodge Avenger. 8.35@165. 4400 DA
250” Neil and Parks Slip Joint. 7.36@183.
4600 DA
242" Mullis Dragster. 6.90@ 200mph
Re: Are there any "small" OEM BB crank pullies? [Re: BANDIT] #2722730
12/09/19 11:51 AM
12/09/19 11:51 AM
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Marion, South Carolina [><]
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I used to run the small Moroso crank pulley w/ a belt driven water pump setup on my 14:1 Indy headed 440. That was years ago in my cuda, ran 10.40s, but ran great on the street. No cooling issues whatsoever, just went through a lot of C12, lol.


CHIP
'70 hemicuda, 575" Hemi, 727, Dana 60
'69 road runner, 440-6, 18 spline 4 speed, Dana 60
'71 Demon, 340, low gear 904, 8.75
'73 Chrysler New Yorker, 440, 727, 8.75
'90 Chevy 454SS Silverado, 476" BBC, TH400, 14 bolt
'06 GMC 2500HD LBZ Duramax
Re: Are there any "small" OEM BB crank pullies? [Re: an8sec70cuda] #2722899
12/10/19 10:04 AM
12/10/19 10:04 AM
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Posts: 15,439
Val-haul-ass... eventually
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BradH Offline OP
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Not sure from where at the moment, but I do expect to get a smaller diameter pulley to try out.

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