Your correct on the theory. The distance between the crankshaft and cam
shaft can vary due to head and block deck heights and head gasket thickness.
If only the belt is being changed you can get away with marking carefully,
locking things and lining the new belt where the old one was on the non
tensioner side. Using a wrench turn the engine over multiple times by hand
before trying to start to make sure nothing crashes. 

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Poppie Jagersand
Sent: Monday, August 22, 2011 6:06 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Timing belt replacement and valve timing in VW gas and Diesel
engines

When replacing the timing belt in a Diesel, the VW instructions say to
(first to lock everything up) then *loosen the camshaft nut* (Then put new
timing belt, tension, tighten camshaft nut etc).� This camshaft nut
re-setting seems to be for precisely setting the camshaft angle at TDC. (or
is there another reason?)

If I remember right (and I may be wrong - it is a long time since), for the
similar 70's and 80's 4cyl gas engines instructions were basically lock up
cam, replace timing timing belt. No camshaft nut loosening and re-setting of
cam timing.

Any reason a Diesel would be more sensitive to (very small variations in)
cam timing? Anyone skipping the camshaft nut part?

Martin (and '82 Westy "Poppie")