I tried lacquer thinner, acetone, and xylol but nothing would touch the sealant until I tried paint remover. I applied it with a cotton-tipped applicator then use a rag and plastic putty knife to gradually remove the sealant. I've got the Volvo remover on order, but got tired of waiting for Tasca to send it, so I picked up a can of Klean-strip KS-3 premium stripper from Walmart this morning. Total cost of repairing the broken exhaust valve was $400 at the machine shop and included surfacing the head, gasket set, new bolts, new valve, and checking the other valves.
Marlin