Michael,

Benzmac has more experience with the sealers than I, but I would share one thing regarding your M103 motor.

I have had good success with the upper timing cover of the M103 by using the blue translucent MB sealer. It has an acetone type smell rather than an acetic acid smell like most silicone sealers. The reason I use this sealer on the upper timing cover is that it will allow the lower U shaped gasket to stay in place while sliding the cover rearward over the shaft seal.

Benzmac may have experience with the black stuff over this seal working as good or better. I use the blue stuff because it has never failed for me. If the black stuff they're talking about is like the "right stuff" that I've used before, it would seem that it would be too tacky to allow the cover to slide over the seal without moving it. These guys experience with the black stuff for this application may prove okay for this application.

I had an old pickup that had an oil leak at the point where the oil pan met the timing cover. It was a pretty significant leak. I took a finger full of the "right stuff" and crammed it into the area of the leak, let it set over night and it never leaked another drop ever again. Amazing stuff!

Good luck with your rebuild,