Ive had trouble with the upper cover of my m104. The eyebrow seal is difficult to compress while fitting the timing cover onto the dowels, leading to a bulging eyebrow seal and minor leaks. Dawned on me one day that I had the head surfaced when i did the valve job and neglected to have the upper timing cover shaved a bit as well. So, if your having trouble with your eyebrow and you milled the head....

__________________
1981 300SD 512k OM603