Pulley help

[bullittwrench]

I was reading an earlier thread about cooling that said to run a 1-1 pulley ratio on gas. I measured our pulleys today. The crank pulley is approx. 4.25" where the belt rides on it and the water pump pulley is approx. 6.75". This would be 40-50% reduction wouldn't it? What diameter pulleys do I need and who has them? Engine is a 415 all alum. on gas. I'm located in central Pa. Putting in a new radiator, shroud, 18" fan and ducting the front end so I want the pulleys to be right too.

Thanks

[billetbirdcage]

Take the lower pulley diameter and divide by the upper diameter to get the pulley ratio. Yours being a 4.25/6.75 = .6296 - 1.0 = 37.03% reduction.


It will depend on how many RPM you turn as to what ratio you need. If I remember correctly Stewart wants the pumps to turn around 7000 rpm wnt you at max RPM's. So if you are turning an engine around 8500 then a 15% reduction pulleys will put it at 7225 at the pump.

I generally use 10 to 15 reduction pulleys as most my engines turn around 8000 to 8500.

Do your self a favor and get hard anodized pulleys as the cheaper ones will wear out the groove in the pulleys and then the belt rides on the bottom of the belt instead of the sides of the grooves. Once the pulley wears and the belt runs on the bottom of the belt it will slip when it has a high load on it and you won't notice it.

I've had good luck with the coleman pulleys or the ones Feger's sell's (look just like the colemans but a different color).

[bullittwrench]

Got on Stewarts site and it says for race apps., max. water pump speed is 6000 rpm. We turn the motor around 8000 rpm. What reduction do I need?

Thanks

[billetbirdcage]

That works out to 25% reduction to get it at 6000 RPM, but I would go off the 7000 as that what has fixed alot of heating problems. I swear it used to say 7000 RPM, they may have changed that since Steward got bought out (I Believe) and could be to make it easier on there pumps. I know not as many people use the steward pumps (professional racer) as they used to, have been told the quality isn't as good as it once was.

Usually a 10% reduction is good for motor around 7500 to 8000 and 15% works good on engines 8000 to 8500.

I'd go with the 15% reduction pulleys myself.


That is just my take on it.

[bullittwrench]

I can't find 15% red. in the Speedway catalog. Poske doesn't list them either. Hmmm, where do I look now? Thanks for your help Billet. By the way we trashed the 02 car you helped me with. Will have an 07 Smack ready to run in 2 weeks. If I get pulleys, LOL.

Thanks

[billetbirdcage]

Call Lou Feger's racing equipment in MN, 1-800-328-3618 ask for Mike, Brain, or Sarah. I measured a set I have from them and they are roughly 5.875 on the lower and 7" on the upper for a ratio of 16% underdrive. They should have them in stock. You should be able to get them in 2 or 3 day depending on UPS from there to you.

They are black anodized. Just be aware there are several pump lengths out there: short, corvette, and long so the lower pulleys have different thicknesses.

If you have a sterward pump and know the number you use, you can look up the pump length so you know what pulleys to get. I always used the corvette length ones which are about a .100 longer then the short pump so they require a thicker lower pulley.

If they don't have any or you can't find them quick enough, I'm pretty sure I have a new set upstairs I could send you if needed.

[billetbirdcage]

Here are the colemans


http://www.colemanracing.com/catalog/index.php?cPath=20_280

[bullittwrench]

We run a short pump, small shaft, but it's spaced out for our gear drive so I'm not sure how to handle that. The crank pulley will need spaced out I guess.

Thanks

[billetbirdcage]

Just get a set for the short pump and then get a spacer/shim kit for the thickness or the gear drive plate or any other water pump spacers you have on there.

I wouldn't get a set from speedway they don't last 1/2 a season before the groove wears out on the lower pulleys. Get a good set and they will last you for years and years.

[2dumb2kwit]

I got a nice set of serpintine(sp) pulleys, and ps bracket from jones racing prod. They worked out to 12.5% reduction. Jones isn't cheap, but they have nice stuff.

[No Rookie]

Hey Bullitt, You have a guy in your backyard that stocks that stuff. We get a lot of our stuff from him. Give H&H a call.

[WestlingRacing]

If you spend the money on the Jones surpentine pulleys you probably never will need to replace them unless you smash your rack on them. Way better than Vbelts. Look em up on the web.