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If the timing belt didn't jump (which would have also been unlikely), I fail to understand how a valve could just bend. How does anyone explain that? Valves don't just bend by themselves, the bend from hitting something like a piston or foreign object (debris like a nut, etc if dropped in) and that can only happen if the t-belt jumped teeth (or broke) or something fell in the cylinder. Even if one fuel injector was stuck opened due to high fuel pressure or the was so much gas in the intake manifold that it sucked enough fuel in to fill a cylinder, the liquid couldn't bend a valve. A liquid filled cylinder CAN bend a connecting rod on compression stroke however.
It wasn't me who said not to do a compression test, I still say it should be done. I have alot of engine experience and if a valve were bent from hitting a piston (impossible by your story), once bent, it's done....out of the way. Valves are bent once and then completely out of the pistons way the next time up. Now, you could have a dropped valve seat or guide but I've never seen that with a Volvo white engine. If you're determined to pull the head anyway, a compression test won't matter and even if anything cyl head related is hitting, those pistons are tough and you won't do more than put small marks in them (worst case).
I'd suspect something else which is why I say to get another opinion BEFORE removing your cyl head.
Other special tools? You will need to remove sprockets to replace cam seals and to hold and position both cams for re-assembly. That's shown in the manual. There are tools that hold the cams in front and hold/position cams in back to the upper cam cover before you re-assemble it to the lower half. The cam positions are critical, you can't just be close. I wouldn't try doing that w/o those tools and be certain that the crank is at #1 TDC (crank mark lined up). Then you'll need the two large wing-nut type tools to carefully, slowly lower the upper cam cover downwords before re-installing all the bolts. Those tools are required to overcome the valve spring tension because it won't just bolt down easily otherwise.
The one time I had an 850 injector stick fully opened on me in the shop causing it to hydrolock while cranking, I too heard a metalic noise cranking only. I removed the cylinder and a guyser (sp?) of gas sprayed out cranking. No valves were damaged but a flywheel tooth broke off when it hydrolocked so I then had to replace the flywheel.
I'm telling you that so that you realize that there are other possibilties besides an unlike "bent valve".
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