Am I missing something here?

'79 308 GTS
I'm going to do a belt service this winter. I've ordered belts, tensioner bearings etc. While I'm in there... lower cam bearings and seals also. My question is, if the bearings are on the outside and the seal is on the inside, how do the bearings get oil?

 

The outer bearings don't use the engine oil for the lubricant on the later design -- they use grease and have (built-in) seals on both sides.

 

Thanks Steve.

 

No trouble Dan. If lubrication was the only issue, I'd say that the early design is superior as you can't do much better than a continuous oil bath for a rolling element bearing (and this is the kind of high-speed application where you'd want to use a continuous oil bath); however, the geometry of the early design is poor as it results in a large "overhang" that magnifies the bearing loads for a given belt tension. The sketch below shows how moving the outer bearing closer to the belt centerline (and reducing the "overhang") greatly reduces the bearing loads (and it also reduces the amount of sprocket runout for a given amount of bearing runout):
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Steve,
That makes sense, the new design would be much better. Now, does the oil seal stop oil from getting to the outer bearing, and if it didn't, would oil leak past the bearing? I'm also tracing down oil leaks.

 

That's the plan

Yes (as there is no seal between the outer bearing OD and the housing).

 

Thanks, that maybe the source of the oil leak. By the way, one of us is up pretty late, I think that would be me.

 

'79 308 GTS

Removed circle clip, bearing, lots of oil (the leak has been found), bearing washer, inner circle clip and instead of seeing what should be the oil seal, I saw what looks like a shiny metal washer??? Didn't see this on any parts diagrams. Could this be part of the old seal? If not, how does it come out?
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Sure looks like a spacer or thrust washer in there,
and either no seal, or the seal disintegrated.

Propably not bad idea to get a bearing
that is sealed on the outside anyway.

Savings on oil will pay for the repair.

Scott

PS: great close-up photo !

 

TZ, you may be right. I took a pick and scraped along the bottom of the bore next to the washer and found small pieces of hard plastic. I think the seal disintegrated. The shiny surface is the inside of the seal.

Thanks.

 

TZ, you were right. That's no washer that's my oil seal.
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D308:

Good detective work on your part !

The bigest question remaining is what
caused the first problem. If you know
that, maybe it won't be repeated......

I wonder if:

1) The seal was installed "dry" and
ate itself before the oil pressure got
to the seal area.

2) If there was grease in the seal
initially, to help "bridge" the time from
start to pressure.

3) There was an imperfection on the
part turning inside the seal, and that "ate"
the seal over a period of time ?

Keep at it, and with the nice photo's
which are so entertaining and instructional
for the rest of us.

You might enjoy this thread:

http://www.ferrarichat.com/forum/showthread.php?t=273443

Yes, it's about shocks, but it is
somewhat like your detictive work, too.

Scott

 

Well, as it turns out, the front seal was the same way. I don't think they desintegrated, that was the way they were made. Probably the original seals?? 32 years old and worn out.

Either way, the oil leaks have been found. The front bearing and seal bore was also full of oil. It wont be long before I'll need to start using the dip stick to check to see if there is oil in the engine.

 

Age just kills those seals. They get hard as a rock.

BTW - when replacing the seal be aware that Ferrari offers a new seal which (gently put) is not as accepting of installing with the housing in the car. It has a polymer outer jacket which does not traverse the circlip gland well. Older seal design is much easier.

Steve- Beautiful Free-Body Diagram of the cam drives! Reminds me of Shigley all over again

 

I've got that book!

 

Very nice sketches. Do I understand correctly the later bearing arrangement is not reasonably retrofitable to the early cars ?

Thanks,

GF

 

Yes, that's unfortunately true because the timing covers are machined differently (and each timing cover is match machined at assembly with their original block) and the timing gears/shafts are different. IMO, if you've got the early design, replacing the outer bearings every ~30K miles (or if the seals start leaking sooner ) is a reasonable cost/benefit approach to preventing problems.

 

I can't wait until I have these problems. Seriously, I am not trying to be sarcastic. I seriously want to get my hands greasy on my Ferrari some day.

 

Does this mean that it would be better to pull the timing cover to replace the seals??

 

If you get your hands on the old design seal with the metal outer ring with the ground chamfer - this can be installed with the cover in place. I made two or three futile attempts with the new polymer coated outer ring, and as I drove it into position, the snap ring gland shaved off a bunch of material. So the short answer is, the new seals require the case to be dissassembled. (And that's why I like the old ones ) I believe Rutland has the "old" ones.