I have an 82 300SD with rebuilt engine by the best in Cincinnati. It has run
fine for more than 2 years and went bad 2 months ago. last week a valve
adjustment found a valve in # 2 that was extremely difficult to get loose to
be adjusted. My mechanic did succed but it has very low compression, barely
contributes and sounds like it is missing [which it is and had been for 2
months]. There is no fuel in the oil so it seems there is no leak through
the piston/rings itself. We think a valve guide but do not know and I am not
excited about taking off the head to find out more.
The body is rusty and seems not to be worth restoration [classic as it may
well be], 245K miles.