Machined seal slip ring - (dimensions below)	Slip ring installed on crankshaft

Slip ring on crankshaft installed in engine block
 

In the picture above you should notice a little circle near the front edge of the ring. That mark is the top of a 1/16" diameter steel roll pin. After the ring is installed to the correct position on the flange, a 1/16" hole is to be drilled through the ring and into the crankshaft flange about 1/10" in from the edge of the ring. With the rear plate and oil pan removed this hole is easy enough to drill from the bottom of the engine. The 1/16" steel roll pin is then tapped into place, and the top of the pin is ground down flush with the surface of the ring with a hand grinder. The purpose of this small roll pin is to prevent any movement of the slip ring on the crankshaft when the engine is hot and running. Been there, done that, and don't want to do that again. A small buff mark in the ring at this point is not critical, as the rubber lip of the new seal rests on the ring much closer to the engine block. You can just see a small shiney rub mark from the seal near the edge of the ring next to the engine block. Rather than installing this roll pin, you may prefer to use a high temperature bearing set adhesive to secure the ring. Just to the left of the roll pin in the picture there is a short mark on the ring running from the near edge toward the engine block. This is a very shallow bite mark left by the chucking jaws of a crankshaft grinding machine when the crank was reground once after the ring was installed. This mark also does not affect the seal, as it does not extend into the area of contact for the rubber lip seal. Notice in the drawing below that the original machining of the ring requires a surface finish of 16 RMS as a smooth running surface for the seal.

Slip ring machining