Oil seal identification

[baltobernie]

Rear main seal 1756 engine, s/n 671297. Will it be the "small" or "large" one?

[manoa matt]

Fiat part # 40004290 Rear main seal 1968-1976 (to engine #430594)

Fiat part #40004300 Rear main seal 1976-85 (From engine #430595)

Hope that helps, if not I have a few seals at home I can check. I also have a 76 motor but never checked the motor number.

[fiatfactory]

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[baltobernie]

Thanks, guys. Looks like I have the "later". The reason I'm asking is that my rear seal has leaked from day one following rebuild. The machine shop dismissed my concern regarding a groove worn into the rear journal from a previous failed seal. They were wrong, but I won't spend the money to do the job again.

What I intend to do is take a salvage rear seal carrier to the machine shop, and have them fly cut 0.150" or so from the mating surface, effectively relocating the seal contact point inward by that much. That should do the trick; my only worry would be going too far inward and having the leading edge of the seal extend beyond the journal.

So I'm assuming that both the "early" and "late" seals use the same carrier?

[fiatfactory]

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[baltobernie]

How about two gaskets... similar result to machining the carrier, but you move the seal outwards...

If memory serves, there's not enough depth in the carrier to fit two seals. I was thinking about not driving the new one in all the way to the seat, so as to be on the outside of the groove. But I think machining the surface would be safer.

Can you tell me more about the two-seal solution, maybe with pictures?

[manoa matt]

Not two oil seals. Use two paper gaskets between the block and the aluminum seal carrier. That will push the seal further out on the crankshaft. The next concern would be the bolt holes lining up for the oil pan.

The seals are also directional to the rotation of the shaft. Tiny raised lines on the seal surface direct oil in as the shaft spins, if the direction was reversed, the seal will direct oil out of the seal.

Or try this: http://www.classicricambi.com/index.php ... cts_id=334
Due to the construction the oil seal effectively has 2 sealing surfaces/rings while most oil seals have only one. I can take a picture of the seal later tonight to demonstrate the principle.

[baltobernie]

Not two oil seals. Use two paper gaskets
The seals are also directional to the rotation of the shaft. Tiny raised lines on the seal surface direct oil in as the shaft spins, if the direction was reversed, the seal will direct oil out of the seal.

Duh The eyes see, but the brain does not think
I'm certain the now-defective seal was installed correctly. Not too enthusiastic about the extra gasket; 1.) Not very thick. The old seal spring which wore thru and scored the journal is easily twice as wide as another gasket. 2.) Additional leak potential.

If memory serves, the journal is about .75" wide, so I should have plenty of room on the inside. My goal is to have the machining done on a salvage carrier, so the car isn't taking up garage space while the machine shop works my little job in.

[manoa matt]

I'd try the silicone oil seal first, as it has two sealing surfaces it should work without spending money on machining. Unless you have two rear main oil seal carriers, having one machined is a "no going back now" approach. I have an extra oil seal carrier if you need one.

However considering all the parts and effort that are required to replace a $6 seal after the fact is no fun if it dosen't work, I understand your desire to get it right and not do it over, hence all the thought and suggestions that have been put into the problem.