Need Help with Belt Length

[Dmod81]

I just replaced my upgraded cs-144 alternator with another, and the pulley is smaller. It went from a 3" pulley to a 2.25" pulley. Now my belt touches itself because it is too long.

Should I try to get my old pulley back from the parts store and replace it, or try to get a smaller belt? I have to think there was a reason this alternator came with a smaller pulley than I had on my last one.

Thanks.

'91 Manual Coupe

 

[LT4man]

I believe in the KISS system.

If your old upgraded CS-144 alternator was charging correctly with the other pulley, I would attempt to get the other pulley back.

The smaller diameter pulley will cause the alternator to turn at a slightly higher RPM.

If you feel the alternator should be spinning faster, then buy another belt.

SAVE THE WAVE!

 

[Dmod81]

I was having trouble at idle, so maybe I'll go with a shorter belt then..

With a 3/4" difference in pulley size, should I try a 90.5", 91" and 91.5" belt?

Thanks for your help.

 

[LT4man]

You are very welcome!

If you know the guy at your parts store pretty well, get two or three belts from him. You want the belt to be extremely hard to install.

In other words, you want it to be the shortest it can be, without it being impossible to put on.

I hope this helps you!

SAVE THE

 

[Vettefan87]

That or you could do it the hard way and use a piece of string, or just cut the old belt and cut the extra length off and measure the piece you cut off and subtract from the total length. Either method would work I would imagine.

 

[ecss]

I just replaced my upgraded cs-144 alternator with another, and the pulley is smaller. It went from a 3" pulley to a 2.25" pulley. Now my belt touches itself because it is too long.
'91 Manual Coupe

If you decide to purchase a shorter belt, you can tell if you've selected the proper length belt by looking at the belt tensioner. If you stand by the passenger side wheel well and look at the belt tensioner, you'll see a raised line on the stationary part of the tensioner and two lines on the arm with the pulley that moves up and down.

When you have the new belt on, the line on the stationary part should be around the middle of the two other lines. If the line is not close to the middle of the other two lines, you could damage the tensioner because you've changed it's travel.

If you look closely at the tensioner you'll see it has a mechanical stop that limits the tensioner arm upward travel.

If you have to short of a belt, If the AC compressor kicks on
you may hear a banging sound which is the tensioner arm hitting the stationary part of the tensioner.

 

[Dmod81]

Thanks for all of your help. I got a few belts from napa, and a 91" belt fits perfectly... Now I'm working on the plugs and wires.