I've recently become the maintainer of a fine 1989 740 GL - 230F with about 70K on a rebuilt engine. Over the last 3 weeks the engine has been developing a nice healthy click that seems like it’s coming from the top end. The nature of this click is that it’s more pronounced when the engine is under load or revving up. It’s also a higher sounding click, not a knock.

My skill level:
I've rebuilt VW 1600s, chevy and olds V8s but have done nothing more on Volvos besides a tune-up.

So here’s my plan of attack:
Step 1:
Right now I’m guessing that this is some looseness in the valve train and I’m gearing up to do the valve lash / shim replacement procedure.
(Why shims? Who's idea was that at volvo?)

Step 2:
If that was inconclusive I was going to inspect the timing belt and tensioner.
(Because you never know, well I don't anyway)

Step 3:
If that was inconclusive is was planning on getting medieval on this Swedish bastard by going to get another B230F from the junk yard and rebuild it, because I think the problem could then be a bearing, wrist pin, or other major overhaul issue.

My questions are:

Do you have any other ideas of where to investigate before I get to step 3? Other possible culprits for a noise like this?