Question on Rear Seal housing choice

[MarkB]

I have a choice of using two different rear seal housings. One has a cut-out in it at top. I assume for ensuring oil gets to the crank/seal area? Anyone know which is prefered, which is the later design?

thanks

[PatAllen]

what is the date code on the schoped one ?

i never saw that, i have real seals from early 68' up to late 85's

[MarkB]

Pat,

There is no date code on these housings, I found that kind of interesting.

[PatAllen]

Pat,

There is no date code on these housings, I found that kind of interesting.

oh is that righ ? jeez...i am just off of my parts bins...i am sure i have like 40 of theses in all kind of shapes/conditions. none of them has that groove...the 2 larger holes on its widest area seems larger, they normaly hold alignment dowels...worth a check.

[john_a]

Are you certain the one with the slot came from a 4 cyl M10?

Looks like a rear cover from an M30 big six.

They use the same rear main seal (as do a LOT of later BMW) but a slightly different gasket & cover.

I've not compared the two, don't know if they are interchangeable, but none of the M10 had that drain slot. Check them over thoroughly, in the picture it almost looks like the rear main seal opening is spaced further from the oil pan on the M30 style cover.

[MarkB]

I just checked the new rear seal and realized the housing with the cut-out is for a 6 bolt crankshaft (6 bolts to connect the flywheel) which is a smaller diameter end, and uses a smaller diameter seal. The engine is a '68 and used to have the 6 bolt crank.

When I started rebuilding this engine, I opted to go with the later 8 bolt to utilize the later style pressure plate. I just still had this part lying around. Curious that they had the cut-out there and eliminated it.

Thanks for the replies!

[john_a]

I just checked the new rear seal and realized the housing with the cut-out is for a 6 bolt crankshaft >>>

Curious that they had the cut-out there and eliminated it.

All right, that confirms the visual difference I mentioned in my last reply, where I noted the rear seal bore appeared further from the oil pan.

The six-bolt rear main seal is 100 mm OD vs 110 mm on the eight bolt, so the smaller seal bore IS further (5 mm ) from the bottom edge of that cover.

And I was wrong when I said none of the M10 covers had that slot feature, I was thinking more about the eight bolt covers, which are a lot more common (I've got a one new spare, and plenty of used and none have the slot.)

So that cut out drain slot was used on the various rear covers before and after the eight-bolt M10, but I never paid attention to it.

[MarkB]

Now I'm curious, what's the slot for? I assume to direct some oil onto the gasket crank interface...

[Guest Anonymous]

It's there to allow oil to drain away from the rear main seal, and fall back to the sump. That's why I referred to it as a drain slot.