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Author Topic:   belt pullies
BayouGent
Dirt Forum Racer

Total posts: 87
posted May 13, 2002 02:03 AM
I'm looking to slow down my belts but our rules state that we aren't allowed to run a reduction pulley on the harmonic balancer. Does anyone know of any chevy trucks or cars that may have come with smaller drive pullies on the harmonic balancers? Most I have seen are all the same size, even some of the older pullies that were on engines with the "short" water pumps. I'd even use a ford or chrysler part if it bolted up on a chevy engine. Any input will be appreciated.

WesternAuto17
Dirt Freak

Total posts: 248
posted May 13, 2002 01:29 PM
Don't forget that bigger pullies on the water pump and alternator will accomplish the same thing.

I read once that a Chrysler slant 6 crank pulley works, but that's second hand.

ryan
Dirt Freak

Total posts: 430
posted May 13, 2002 01:52 PM
If you want to slow your belt speed down you would want a bigger pulley wouldn't you. What exactly are you tring to accomplish do you just want to underdrive your water pump or just make everything turn slower. I have to disagree with western auto on the bigger pullies on the pump and alt. Those bigger pullies will turn those two devices slower equalling less water and less alt output, but won't do a thing to actually slow the belt speed because the main pulley is the drive pulley and the speed of the belts wont change unless you change that particular pulley. JMO

Pickel
Dirt Forum Champ
Total posts: 564
posted May 13, 2002 08:06 PM UIN: 25419780
I run the lower pulley off of a Chev. 6 cyclinder that is the same size as my harmonic balancer. I run a waterpump pulley off of an old Pontiac 400 motor. They are a double grooved pulley. If you can't find an old Pont. get one off of an old slant 6 Dodge truck. They're almost as big as the Ponitacs

WesternAuto17
Dirt Freak

Total posts: 248
posted May 14, 2002 09:16 AM
Ryan - you're right about the accessories. Not changing the crank pulley will just slow the accessories and not the belt. Turning accessories faster takes more hp.

If you're having trouble keeping belts on, that's a good thing when you're turnin 6,000 rpm.

However, the crank pulley needs to be smaller to underdrive everthing else, not bigger. You want the ratio of rmp's of the crank to go up when compared to the accessories. If the 2 pullies are the same diameter, the ratio is 1 to 1. If the alternator pulley is 2 times bigger, the crank will turn twice for every one time the crank turns. IMO, at racing rpm's, you can give up that output.


nWoracing
Dirt Roller

Total posts: 17
posted June 13, 2002 12:20 PM
Hey Murray,Are you talking about something for your bomber car or something different.
We were having problems with our belts and pulleys.One person told me to get a set of deep groove pulleys.So I did.I put them on,
and slung the belts in the driveway.So what
I did was put the stock pulleys back on and went to Tony's Auto Parts.I bought a set of Gates belts,and we haven't slung a belt since.Instead of running a belt from the crank to the power steering,run it from the water pump to the power steering pump.That should slow your belts.

Adios,
Ron Carpenter
(nWoracing)
#31 Pure Stock

Pickel
Dirt Forum Champ
Total posts: 564
posted June 13, 2002 09:06 PM UIN: 25419780
Just a question....If everyone is throwing belts at 5000-7000 rpms how many revolutions does a drive shaft turn? I run my alternator off my drive shaft and it doesn't spit belts.

powerglides
Dirt Full Roller

Total posts: 69
posted June 14, 2002 06:15 AM
Run one belt from your crank to the water pump only and one belt from the crank to the power steering pump only and throw the alt away. I went to this setup a few years ago and have not had a problem since. And if you go to stewarts website they do not recomend underdriving the water pump. Contrary to popular belief an alt does not produce more hp, not under 6500 rpm anyway. my battery shows 12.50 volts after two weeks of running. Read the Battery article in this months Stock Car Racing. (go figure usefull information in that RAG Magazine!) just put a 700+ cca battery in and charge it with a trickle charger. And if you forget one week don't worry about it.

DirtDobber
Dirt Forum Racer

Total posts: 79
posted June 14, 2002 12:18 PM
Glides I did just that 4 weeks ago and have been happy ever since. New belts are cheap insurance also. Just keep a close eye on them and if you have the least doubt replace them. AND keep an extra set with you at all times.

BayouGent
Dirt Forum Racer

Total posts: 87
posted June 14, 2002 04:10 PM
Thanks for the info powerglides. That is the setup I was running on the car before we decided to scrap it and move up to a faster class. I ran an alternator too (rulebook said I needed to) and did not have a problem throwing belts after all the grooves were perfectly in line. What I was looking to do was underdrive the water pump and power steering pumps because I wanted to slow the water down a little to give the radiator more time to cool it (I do use a restrictor plate in thermostat housing) and slow down the power steering pump because some of the stock pumps don't like the high RPM. The last one I installed was hanging in there pretty good though. Anyhow once I get this new car finished we will use a 30% reduction pulley and run the water pump and power steering pumps individually again most probably or possibly run 2 belts around all 3 and see how that works. I just felt that an engine turning 7000 didn't need the pumps turning quite that fast, and 5000 RPM would be more than sufficient for the water and power steering pumps. At least that's my theory anyway.

Pickel
Dirt Forum Champ
Total posts: 564
posted June 14, 2002 09:32 PM UIN: 25419780
the only reason I run an alt. is because I run twin electric fans on the front. I do agree with glide that a battery will last 2 or 3 weeks without a charge but with those fans I need one.

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