To add what Mike has knowledgeably said, you need a device (volvo tool or
your own made one) to pull the top half back down onto the lower when you
re-assemble (against the pressure of the valve springs) and also some wire
both ends to fasten the cams to the top half as you lower them down. There
is an off-centre slot in the dissy end of both cams you can slide a piece of
flat metal into to lock them at 'tdc' position also.

You need about 8 pairs of hands at this stage!

The cam pulleys will need to come off, mark their position relative to the
shafts with tippex or similar prior to releasing them- on some cars they are
NOT keyed to the shaft. Beware.

I would strong recommend using the puller when releasing the top cover to
ensure it comes up evenly- as Mike said you will break the casting if it
does not. It is located on about 8 dowels and it can be tight to release,
but sometimes they pop up of their own accord.

The tools I have are made a-la Haynes from 3 old plugs, the insultor and
innards drilled out and some thread welded on with a cross piece and nut on
the top. The cross piece straddles the cam cover. Install plugs in 1,3 and 5
and you can pull the upper half down squarely very easily, or conversely let
it spring up evenly.

With respect to the sealer, Volvo sell both the removal thinners and the
proper sealer stuff to re-assemble it with.

On *no* account *ever* use instant gasket, or worse silicone, or anything
else. You will have leaks all over the shop if not worse. The Volvo sealer
comes with a fine hair roller, which after you have removed the old sealer
with the thinners you apply a very thin layer with the roller.

The new tappets must be soaked in clean engine oil for 24hrs first, and
during this time use your fingers below oil level compress and release
several times to prime them afew times.

Hope this helps.

Tim...