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Old 05-07-2012, 07:38 AM
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How long V-belt?

Hi. I'm going to put an additional v-belt between the water pump and the crank pulley. Any one know the proper belt length for this?

It's on a small block chevy with short water pump. The pulleys are Ebay bought aluminum ones.

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Old 05-07-2012, 07:51 AM
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Quote:
Originally Posted by staleg
Hi. I'm going to put an additional v-belt between the water pump and the crank pulley. Any one know the proper belt length for this?

It's on a small block chevy with short water pump. The pulleys are Ebay bought aluminum ones.
There is no way anyone can tell you that. Guesses can be made but the best way is to measure it yourself.
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Old 05-07-2012, 08:50 AM
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It took me 3 trips to the parts store when I changed the alternator bracket. What I finally ended up doing is taking an old belt that was known to be longer, then cutting it until it just butted the two ends together. I then looked at the Gates Belt interchange and length list and came up with what I thought was right. First one, a little bit too long, next too short with the third one the winner.

I'll let you do the research as it is a fairly slow loading site and probably worse on your side of the Atlantic.

Dave W
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Old 05-07-2012, 10:10 AM
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Thanks.
Since the distance between the crank and the water pump are equal on all small blocks, I thought maybe someone knew, but I take the point.

The tip with the old belt was good.
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Old 05-07-2012, 10:40 AM
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Belt

do the old math way... calc the circumference of ea pully and divide ea by 2.. measure the center to center of ea pully and times that by 2. add the 4 numbers and that'll get u really close.
i used the old belt trick too....
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Old 05-07-2012, 01:29 PM
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Quote:
Originally Posted by staleg
Thanks.
Since the distance between the crank and the water pump are equal on all small blocks, I thought maybe someone knew, but I take the point.

The tip with the old belt was good.
Not all pulleys are the same diameter and some of the aftermarket pulleys are underdrive and have a deeper groove to prevent belts from flying off at high RPM's,so the old belt trick is a good bet to allow for adjustment you could go 1 1/2" shorter and longer and keep your receipt and return the belts that won't fit.Been through that with my March pulleys.
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Old 05-07-2012, 03:23 PM
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get an old 1/2 belt thats too long, cut it, put it around where you want it, mark how long it would be and measure

edit...Oh, didnt read Daves post.......lol
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Old 05-07-2012, 03:48 PM
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Why not just do the simple math involved and buy the right length belt the first time?

The correct way to measure belt length is to first of all know the diameters of the two pulleys in question, and the distance between the centers of the two pulleys.

Say one pulley is 5" in diameter and the other is 4" in diameter. Multiply both pulleys by PI, which is 3.1417, add the two together, and divide each by 2. 4" times 3.1417 is 12.56". 5" times 3.1417 is 15.71". 12.56 plus 15.71 is 28.27, divided by two is 14.135".

Now measure between the center of the two pulleys. Say that distance is 18". Double that to equal 36" and add 14.135 which equals 50.135. That means for this example, you need a belt that is 50" in outside circumference. If the pulleys are "A" pulleys, you buy an A50 belt.
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Old 05-07-2012, 05:20 PM
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Quote:
Originally Posted by S10 Racer
There is no way anyone can tell you that. Guesses can be made but the best way is to measure it yourself.
X2 on this. get the pulleys then do the measuring after they are on. JMO




Cole
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Old 05-08-2012, 01:02 AM
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Old machinist trick is to use a length of rope the same diameter as the widest face of the vee belt, wrap around the pulleys and mark the length once you pull the rope tight.

It will be within millimeters of the right length, done it a thousand times...old machinist LOL!
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Old 05-08-2012, 03:10 PM
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Quote:
Originally Posted by 4 Jaw Chuck
Old machinist trick is to use a length of rope the same diameter as the widest face of the vee belt, wrap around the pulleys and mark the length once you pull the rope tight.

It will be within millimeters of the right length, done it a thousand times...old machinist LOL!
Yep done that before also works really good to.
I was going to say this but thought everyone might think i was nut's or something.


Cole
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Old 05-08-2012, 06:22 PM
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no one has mentioned you can't put a belt on 2 pulleys with no adjustment?
you need a third adjustable pulley like an alternator, ps pump or ac compressor.
even if you bought the right belt to fit, it wouldn't fit in a couple of weeks from stretch or wear.
if it stayed on the pulleys it would slip so bad if the other belt broke, your pump would barely turn
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Old 05-08-2012, 09:51 PM
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There are millions of industrial applications in the world that do not have a third pulley that is adjustable. While it is true that most belt and pulley systems have a way to adjust them initially, that is a convenience, not a necessity. What you are saying is that every belt needs constant adjustment to account for wear and stretch. That is not remotely true. How often have you ever adjusted your belts?
Have you ever adjusted the belt that runs your air compressor? How about the one that runs your refrigerator or your table saw or your furnace fan or your snow thrower?
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