I'm rebuilding a B21F cylinder head. The valve seats and margins needed grinding. When I reassembled the head, I had zero valve clearance on 4 of the valves. I cut the valve stems by .02", but still had no clearance. Bentley says that the maximum I can cut the valve stems is .02" What would happen if I cut the valve stems more than .02"? Besides adding thinner shims, is there anything else I can do to fix this situation? Thanks in advance!

Assuming the valves were close to normal lash before the valve grind, and you cannot get any lash after removing .020 from the valve tip, then you have ground an excessive amount from the valve face and the seat. Volvo specs a maximum protrusion of the valve towards the cam to keep the tip height within the range of shims - they have a checking mandrel for this operation. You have somehow exceeded this. You may be able to purchase thinner shims, but my first concern is why the valves have sunk so far into the head.
Removing any more from the tip is not a wear concern. The bucket relieves the valve tip from needing any extra hardness, such as valve that had rocker arms rubbing on them. Rather it is needed to prevent the bucket from contacting the retainer and loosening the keepers.
New valves maybe. New seats maybe. New head would be cheaper.
Try and shim them into adjustment.

I'm puzzeled by your question. The normal procedure is to purchase appropriate thickness shims. I would presume that you can get them for nearly nothing at a junk yard. I have always purchased new ones at the Volvo dealer, but I never needed more than two or three at a time, so the cost was less expensive than the trip across town.

I presume that the reason that you should not cut the valves any more is that they are hardened on the end.

It's a non-turbo head/engine, so sodium/stellite is not an issue.

I thought maybe the reason for not cutting further would be because they are sodium filled; presumably, going further would cut into the cavity that holds the sodium.
--
David Armstrong - '86 240(350k km?), '93 940T(270k km), '89 240(parts source for others) near Toronto

Gee, I would have never expected to find sodium in any Volvo valves, but what I don't know fills volumes. I've seen sodium only in air-cooled Porsche valves. In any event, I'd expect sodium core to extend only to the end of the valve guide. Others may straighten me out on this.