I'll tell you my story. For the people who don't know, i'm from chile and i've a catera (an Opel Omega really). A month ago i had a problem with the heater valve. It was leaking. So i send the car to the dealership. They said Ok, we will fix it, but we must measure the cylinders compression. I wasn't worry, because the car hadn't power or economy problems, but the results weren't good. 2 cylinders had very little compression (about 50-60 psi) and the others were low, but not so bad (arround 180psi, i think). Then, they must take off the cylinder head. The reason for the very low compression in the 2 cylinders was an old head gasket, and the low compression in the others cylinders were by a sealing problem of the valves, they wear out. So, i must replace the valves. The intake valves cost me here in chile about 15 dollars each, which isn't so bad, but the exhaust valves....120 dollars each!!!! the reason: they are filled with sodium.
So they send the head to an engine repairshop, to make a measurment. I could save the exaust valves!!! and the head was ok.
Now they're finishing the job, i hope it last.
I'll informe you, when it is ready