[V8] belt tensioners

[Scott Simmons]

Timed and tensioned the car today, and all that crap got me thinking (uh 
oh).

It seems as if the V8 has two tensioners for the timing belt and two for 
the serpentine belt.  For the T-Belt, there's two eccentric rollers:  
the one on the right bank and the one attached to the shock.    For the 
serp belt, there's the spring loaded tensioner but it's bolted to a 
shock of its own.

What gives?

I've done a lot of t-belts on 944's.  The early ones had a simple 
eccentric roller.  It was extremely easy to time and tension the belt.  
If a pulley was one tooth off, it took about 10 seconds to correct.  I 
had a cam one tooth off and I had to adjust so much just to get some 
slack.  The later 944's and a spring loaded roller, but it was still 
easier than this.  Never got too involved in a 928's belt, but I know 
they're regulated by oil pressure (as are 968's).

How does the T-Belt shock-and-roller combo combine with the other 
eccentric roller?

Why does the serp belt need a shock that seems to act opposite of the 
spring tensioner?

~Scott Simmons