Datsun Roadster Forum-311s.org

Thanks JT, but, the ID's are not the same.

U20 damper seal surface is 48mm (measured)
R16 damper seal surface is 45mm (measured)

Looking up the seal part #'s shows same.

A 3mm difference is not something I'm willing to ignore....a second time.

Yes, so the 1.6 IS 45mm, 47.8 for the 2L. So that is 1.4mm larger radius difference which would not bother most lip seals (and of course its oil lubricated).

Most strokers I have seen ran a 1600 pulley, but I've seen the u20 damper used too and never heard of a leak problem with the lip seal.
(could also be brand specific on the seal). I checked a new R lip seal and it slips right over, not excessively tight.

Where ever you looked up the part numbers, that is wrong, I can assure you R&U are different.

If you are really concerned about it, its about 15 minutes on a lathe to go from 47.8 down to 45/46 or you could try to source an aftermarket metric seal.

Thanks for clearing that up.

I meant, above, that the seal IDs matched the measurements...

It is a tight fit, so likely I'll have the U20 damper turned down and polished.

Had the U20 damper turned down to 46mm. I'm more comfortable with that....

Also had a look around....Timken has a shaft oil seal 48x68x10-RLS35S which looks to be the right dimensions for the U20 damper in the R16 cover. Don't know if it would be suitable for an automobile, but, it is something I'm going to look into.
Seems there should be a non-stock seal we could use for this....maybe...

Engine machine shop I've been working with says the 'double lip' shaft seal should be fine.
AVX Seals has a listing that should work well for the U20 damper in an R block #TC48x68x12
Others should be available....

Picked up a seal that will work for the U20 Damper with R16. (48mmx68mmx11mm)

Nice find and research Daryl.