Moparts

Are there any "small" OEM BB crank pullies?

Posted By: BradH

Are there any "small" OEM BB crank pullies? - 12/06/19 04:02 PM

As in smaller than standard, but not as small as the Moroso cast pulley?
Posted By: AndyF

Re: Are there any "small" OEM BB crank pullies? - 12/06/19 04:30 PM

Doty makes them but the spacing might not be what you need. His small pulley is designed to use with an ATI damper and a stock water pump pulley. March also makes smaller diameter pulleys for Mopar. They have a couple of different offsets.
Posted By: GY3

Re: Are there any "small" OEM BB crank pullies? - 12/06/19 05:03 PM

Originally Posted by BradH
As in smaller than standard, but not as small as the Moroso cast pulley?


What's wrong with the Moroso pulley? I run it on the street and never have any cooling issues.
Posted By: John_Kunkel

Re: Are there any "small" OEM BB crank pullies? - 12/06/19 05:25 PM

The smallest factory crank pulley I've seen is 6 1/4" in diameter and 2" high to the center of the V.
Posted By: BradH

Re: Are there any "small" OEM BB crank pullies? - 12/06/19 05:52 PM

Originally Posted by GY3
Originally Posted by BradH
As in smaller than standard, but not as small as the Moroso cast pulley?


What's wrong with the Moroso pulley? I run it on the street and never have any cooling issues.

Other people who have used the Moroso pulley have said they had cooling issues because of the reduced water pump speed, so I'm not 100% confident it's the way to go.

I'll do some more research based on everyone's responses above. scope
Posted By: Roughbird72

Re: Are there any "small" OEM BB crank pullies? - 12/06/19 05:52 PM

I'd have to check out the diameter of the March I've been running, I know it was smaller than the stock pulley.
Mancini lists a crank pulley at 5.2"
Posted By: DusterKid

Re: Are there any "small" OEM BB crank pullies? - 12/06/19 07:57 PM

440 Source list their pulley as 5.25". I use one on my race car and it works fine.
Posted By: AndyF

Re: Are there any "small" OEM BB crank pullies? - 12/06/19 08:13 PM

The Doty pulley is 5.75 diameter. I've run this one for years in my Coronet without any overheating problems. I use a factory water pump pulley and an Edelbrock water pump. I have a 22 inch radiator so it isn't exactly a killer cooling system.

I have the same size pulley on my Duster.

https://www.dotymi.com/mopar-crankshaft-pulleys/42-mopar-and-chevy-crankshaft-race-pulley-1375.html
Posted By: AndyF

Re: Are there any "small" OEM BB crank pullies? - 12/06/19 08:16 PM

Here is the setup I use on my Duster. It seems to stay cool but I haven't tested it yet in hot weather. This is a custom version of the Doty pulley. I had him add a mounting ring on the backside of the pulley so I could bolt on a trigger wheel. That way the wheel is independent of the mounting surface so the pulley height doesn't change.

http://arengineering.com/products/efi-trigger-wheel-for-stock-water-pump/
Posted By: TRENDZ

Re: Are there any "small" OEM BB crank pullies? - 12/06/19 08:43 PM

I can build you a pulley in any configuration you want if you can supply the needed dimensions.
Posted By: gregsdart

Re: Are there any "small" OEM BB crank pullies? - 12/07/19 02:25 AM

There is another company that makes beautifulreduced size pulleys for mopar, including crank, water pump and alternater pulleys. For the life of me i cant remember thier name, but they sure looked good on the 408 i built! I think they were out of Minnesota? Google aluminum pulleys and see what pops up.
Posted By: BSB67

Re: Are there any "small" OEM BB crank pullies? - 12/07/19 02:28 AM

Note to self....look up what OEM is.
Posted By: gregsdart

Re: Are there any "small" OEM BB crank pullies? - 12/07/19 02:35 AM

Originally Posted by BSB67
Note to self....look up what OEM is.

Maybe small oem doesn't exist?
Posted By: gregsdart

Re: Are there any "small" OEM BB crank pullies? - 12/07/19 01:35 PM

If you decide to go aftermarket, TRENDZ (Rick) can make a nice piece that will give you the exact speed you want to run an alternater, etc at. He made a double for me for my bracket car that turned out very nice!
Posted By: BradH

Re: Are there any "small" OEM BB crank pullies? - 12/07/19 02:11 PM

Off the top of my head...

Looks like OEM replicas are listed as 6.25"... about an inch wider in diameter than some of the aftermarket pulleys I found.

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.

My cruise RPM at 65 MPH is about 3500. I don't know how much higher that is than what the OEM pulley spec was designed to work with.

The car has a 26" OEM radiator, MP aluminum housing, Edelbrock pump, and uses a 160* thermostat.

There's nothing functionally "wrong" with my OEM water pump pulley. I see there are aftermarket w-p and alternator pulleys, too, but a$$ume they aren't required as long as the v-belt style is used (as opposed to the serpentine belt conversions).
Posted By: mopar dave

Re: Are there any "small" OEM BB crank pullies? - 12/07/19 04:21 PM

Brad, not sure this helps you or not, but I use Marsh serpentine pulleys. The WP pulley is 4.5" and the crank pulley is 5.25" measured inside where the belt rides. This combo cools my 400 block with a mechanical fan real nice. My block is filled nearly to the top of the deck as well.
Posted By: AndyF

Re: Are there any "small" OEM BB crank pullies? - 12/07/19 04:25 PM

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.
Posted By: gregsdart

Re: Are there any "small" OEM BB crank pullies? - 12/07/19 05:36 PM

Originally Posted by BradH
Off the top of my head...

Looks like OEM replicas are listed as 6.25"... about an inch wider in diameter than some of the aftermarket pulleys I found.

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.

To figure what i needed i took the max alternater rpm. As my target, then from the alternater pulley diameter and my max engine rpm i came up with the size pulley i needed. Since most all of us run more rpm at cruise than a stock setup it works well for the water pump also. Mymax rpm on the 408 was 6200 and a 5 inch pulley was about perfect. I had 3.55 gears and an auto.
Posted By: BSB67

Re: Are there any "small" OEM BB crank pullies? - 12/07/19 08:50 PM

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.
Posted By: GY3

Re: Are there any "small" OEM BB crank pullies? - 12/07/19 09:49 PM

The Moroso is 5".

Funny aside about the Moroso pully: I do my best to hide any aluminum and aftermarket mods in my engine compartment. I installed the aluminum pulley out of the package thinking it was buried to where no one would really see it. I went to a local cruise spot and literally the FIRST guy that walks up and looks at the engine points and says "Oh, it looks like you have an underdrive pulley!"

I went home, ripped off the pulley and immediately painted it black! primer
Posted By: AndyF

Re: Are there any "small" OEM BB crank pullies? - 12/07/19 10:26 PM

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.

Attached picture DSC_4040 (Large).JPG
Posted By: mopar dave

Re: Are there any "small" OEM BB crank pullies? - 12/07/19 10:49 PM

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?
Posted By: BradH

Re: Are there any "small" OEM BB crank pullies? - 12/08/19 04:29 PM

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+".
Posted By: BradH

Re: Are there any "small" OEM BB crank pullies? - 12/08/19 04:34 PM

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...
Posted By: HOTMOPR

Re: Are there any "small" OEM BB crank pullies? - 12/08/19 05:00 PM

Not OEM but its small..

www.hughesengines.com/Index/product...e=partnumber&page=4&partid=30955
Posted By: AndyF

Re: Are there any "small" OEM BB crank pullies? - 12/08/19 06:39 PM

Originally Posted by HOTMOPR


That is the Doty pulley.
Posted By: BSB67

Re: Are there any "small" OEM BB crank pullies? - 12/08/19 07:06 PM

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.
Posted By: BradH

Re: Are there any "small" OEM BB crank pullies? - 12/08/19 07:33 PM

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.
Posted By: BSB67

Re: Are there any "small" OEM BB crank pullies? - 12/08/19 09:18 PM

I kinda figured that you probably knew. I know that I've raced to real stuff back in.
Posted By: BANDIT

Re: Are there any "small" OEM BB crank pullies? - 12/08/19 09:35 PM

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.
Posted By: an8sec70cuda

Re: Are there any "small" OEM BB crank pullies? - 12/09/19 03:51 PM

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.
Posted By: BradH

Re: Are there any "small" OEM BB crank pullies? - 12/10/19 02:04 PM

Not sure from where at the moment, but I do expect to get a smaller diameter pulley to try out.
© 2024 Moparts Forums