Serp belt question

'87 Turbo "T"

What a complete shitshow!!
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Hey everyone. I’ve searched & read the belt length threads, however is anyone using a 1600(just a CH under 63”) belt?

I had a 1620(63.7) & my tensioner was at the upper limits. I went to a 1615(63.5) & it started ok, then once it stretched is close to the upper limit on the tensioner again.

So it seems that a 1600 may be correct for me. As far as I know, my pulleys are all stock. Seems kind of short unless someone changed the alternator pulley before I bought it.

I generally buy a gates brand , number ends in 635 or 640 I think. Depends on the wear on the tensioner spring and how the accessories get bolted back on for some stacked tolerance. Funny how things can get way off if you take em apart and put em back together repeatedly.
Thanks. New tensioner from G-Body parts. Unless this pulley is a different size.

Just seems short to me. Unless maybe the A/C compressor pulley(from Highway Stars) is different. Or someone changed the alternator pulley.

Pretty sure water pump & crank pulley are stock size.
Boy this is odd. Measured my pulley, 2-3/4”. Subtract the 1/8” for the lip 2-5/8.

I know & most people are using the 63.5”. Wonder how I got a 1-2” shorter.

Also I’m using a Bando belt. Made in Merica. Not sure if that has any pull here
4060635 here with brand new G Body Parts reproduction tensioner 👍
Well I'm at a complete loss. Tried the Continental 63.5 belt & it's almost out of the window again.

The only belt that seems to stay is the old 1618mm GM belt. That one barely stretches. The only difference I have noted is that all of the new belts are thinner. The old GM belt is roughly 1/4" thick. The other belts range from 1/8"-barely 3/16" thick.

Or the construction of the new belts is crap. LOL