Why would you bring your mercedes head to a machine shop that could not work on Mercedes heads?

It really depends on the milage, if its lower milage, probably under 100,000, then your probably ok, but over 100,000 you might as well, particularly if you have a commitment to the car (i.e. you like it and intend on keeping it) as blowing a valve is much worse than a head gasket as you run the risk of damaging the piston and the cylinder walls. But if thats a risk you want to take, go for it, its not my car, or my $3000+.

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1985 190E 2.3-16v Euro
1980 300GD SWB