Crankshaft Roll Pins

[frankr]

So simple.  The gasket and plate provide a flat surface on the crankcase.  If installed correctly, you would glue the gasket to the plate with a bit of sealer.  Everything below that comprises the seal which rotates on the plate’s surface.  Yes, everything rotates with the shaft except for the plate which stands still.  A thin film of oil lubricates the sliding surfaces.

There are only two ways fluid can get past that plate–around the outside, which is blocked by the gasket, or through the center hole which is blocked by the drive shaft, carbon seal, and o-ring.

Yes, the roll pin holds the whole assembly up against the plate.

[Mumbles]

The gasket is glued to the block, the plate is glued to the gasket, or at least they should be to prevent the gasket from oozing out over time.  The pin, which I’ll call a drive pin as that is what it is doing here, drives the cup and the rest of the seals components. Any fuel mix coming thru the bottom bearing lubricates the surface between the plate and the carbon seal. The O ring prevents the mix from running down the drive shaft.

Since the surfaces between the plate and carbon seal make the seal, both surfaces have to be smooth with no pitting. The original plates were made of brass, which tended to wear out and develop a deep groove in them from friction with the carbon seal. Around ’55 or so they started to make them out of stainless which was far superior to the brass.

That’s about as simple as I can explain how this seal system works. Maybe someone with more knowledge or experience can add something to this.

[Steve D]

Those are 2 of the best explanations I ever heard. Thank you both!

2 users thanked author for this post.

Mumbles, frankr

[Mumbles]

Looks like that frankr guy beat me  by a few minutes.  😄  I have to learn how to type quicker!

[Author]

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