If the cam lobe, rocker, and ball stud are OK, then this is not the problem. I don't see how it could stick shut.

BTW. I bought a 380SL with a rocker worn so severely that the valve was not opening at all. The "ball" part of the ball stud had popped out and was laying on the top of the head.

Picture attached.

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__________________
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