Vacuumhead asked -- "Also on commercial diesel motors you can sneak out the main bearings by turning over the crank while running a shank through the oil hole. Will a similar technique work with the Volvo?"
Yes, the Volvo main bearing can be pushed around--get them started by pushing on one edge (the one opposite the locating tab), then rotate the crank and it will follow along--maybe with a little nudge on the now exposed other end.
I'm making this post in response to Unkel Udo II's post regarding the advisability of changing out rod bearings that can be heard with the motor warm. In my own experience that will only be successful if the rod rattle is only heard when first firing up the motor. A rod rattle when warm usually requires machining the crank journals. The one time I let a client talk me into changing out rod bearings that were clearly heard when warm resulted in a quiet motor--for about 5 minutes (1959 Ford Pickup 6 cylinder). It may work but I have my doubts.
Others have probably suggested this -- are you sure it's rod knock? A split exhaust gasket on one cylinder can sound an awful lot like a rod knock. I'll be doing just such a job later this week - the client said his neighbor told him he had a knock - and it just might be - but pulling the plugs to make sure they were in properly revealed a boot with obvious exhaust exhaust damage. The gaskets will be in soon and then we'll see. -- Dave