I am working on a 1985 380SL with 201K. It has several flat cam lobes and a variety of other problems. It was running very badly but had oil pressure. I changed the oil and spark plugs, and got the control pressure more or less correct, verified spark, etc.

I was attempting to start it by cranking, richening the mixture a bit, cranking, etc. Each cranking burst was less than ten seconds. On the third or fourth crank, the engine stopped turning over. It would not budge with the starter. The starter has a good clunk when you hit it.

I put a socket/breaker bar on the crank hub. It will not budge a millimeter in either direction.

I pulled the cam covers. All of the the rockers are in place. No obvious problems with timing chain or slide rails. Pulled the plugs out. Removed the tensioner and pulled the sprockets off the cams. None of this made the slightest difference. This thing is stuck as tight as [supply your own phrase].

Any ideas about what could go wrong at cranking speed that would lock up an engine?

Thanks,

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe