Followed FAQ pages and Haynes to replace all three seals, tensioner and t-belt. This was my first time doing on the Volvo and first time period....
All in all it went pretty smooth. It took me a total of 8 hours, though I am anal about having a clean engine and compartment. The Cam Seal was leaking since October, so every thing was in need of be degreasing, which added a couple of hours.......

That is just background, but my real question has to do with the marks on the replacment timing belt. Also, the Volvo t-belt I was replacing did not have marks, is that typical? I instaled the new belt (conti) using the marks. I then rotate the crank by hand and the pulleys all are tdc, but the belt marks are off? I take the belt off and reinstall. I once again rotate the crank by hand and again the pulleys are at TDC, but the belt marks are off?

I then take a chance. I put the Crank pulley back on and again verify TDC. Leaving the Accessory belts off, I then start the engine. It appeared to run almost normal. Since it was running just of the Battery, I then assumed all is well.....

I buttened every thing up and took her for a road test. No problems, looks like I did it.

So, why do the marks move? Is this normal?

The belt marks are only in alignment when you slip the belt on, after 1 rotation they will not align again because there is a different number of teeth on the lower and upper pulleys. The number of belt teeth would also have to be an exact multiple of the pulley teeth. I suppose eventually you may get an alignment, perhaps some ambitious Brickster might count teeth and do the math.

It is however important to rotate the engine after belt installation, take up all slack on belt and double check timing. To do this you can rotate engine backwards and forward.

Personally I never use those belt marks, I would rather trust the factory marks on the engine, I know they are right.
--
David Hunter

> So, why do the marks move? Is this normal?

Yes, it is. The TB length is not an even multiple of the pulley circumference, so the TB marks will shift in relation to the pulley marks. They're an aid to installation, and of no value thereafter. If the pulley marks line up with the marks on the cover, you're OK.

Look at it this way (using values chosen for easy math, not neccesarily reflecting reality):
Suppose you had 30 teeth on the cam and intermediate pulley (and thus 15 on the crank) and 120 teeth on the TB, and all the marks lined up at installation. After 4 rotations the TB marks would again be on the pulley marks. Now suppose the TB had 125 teeth rather than 120. After 4 rotations the TB mark would be 5 teeth behind the pulley marks. In both cases the pulley marks would still be correctly lined up in relation to each other and to the marks on the cover.

By the way, if you have the head mounted distributor (in the US market the 900 could have either a head mounted or a block mounted dist) the intermediate shaft is not critical as the only thing it's driving (as far as I know) is the oil pump.

Bram

I dont use marks on belts / I line up outer crank belt guide mark to
11:00 mark on casting, cam to 12:00 position mark on top center, and
intermediate shaft to 3:00 (or so) mark all as listed here in FAQ. The
timing is easily set if you "line it all up" -before disassembly- and make
some secondary reference marks with white out, I mark the pulleys and block
and proceed as per FAQ, when all done make sure the secondary marks still
line up. I did a timing belt last weekend and was paranoid thinking I may
have been off 1 tooth, turns out I had it right. supposedly 1 tooth off
would have been very obvious as I was told on posts here.