I've got 71 2.8 mercedes 6 cyl with low compression (130) in just one cyl,
compared to 140-150 in the others. Unfortunately cyl on either side of the low are 140 and 150, worried about that imbalance . Overheated at some point- machined the head, new gasket ,no valve work just re-set. Walls of
cyl #5 are not nearly as clean as the rest