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Relevant to all the engines, and probably more of you have done this mod to the 350 than the 501 so posted here as well:

My 501 ate a crank oil seal at Cadwell. Anyone seen this before? some details:

Engine rebuilt in 2007/8, new seals throughout (obviously)around 4000km covered since.

Engine is a late 501 with the alternator side roller bearing modification.

The crank oil seal face is completely detached from the rest of the seal.

There are radial cracks inward from what I think is the seal lip edge (a bit hard to tell on the mangled strip which is left) which look like the rubber has perished and cracked, but the rubber feels supple still so this could be secondary damage I suppose

I cant feel any play in the crank bearings.

I had a look at my spare 501 motor (also with roller bearing conversion) to get the oil seal code, and discovered that this seal also shows signs of damage. There is a clear witness mark around the seal face, and has split all the way through around 1/3 of the way around (see photo below- this is the seal from my spare motor, but the failure mode I suspect is the same as happened at Cadwell).

Maybe the dished washer behind the timing belt could have been rubbing on the seal, but how? Crank axial expansion in the roller bearing pushing the seal against the lower pulley/dished washer?

I'm reluctant to replace the seal blindly if this is going to keep happening- it's not the sort of job I want to add to 'service items' Has anyone else experienced this, particularly on engines which have had the timing side roller bearing modification?

And while we're at it, can someone tell me the correct code for the crank oil seal, as both of mine are damaged beyond reading. In fact, I might replace all of the external seals just in case- if anyone has a complete list of the codes that'd be handy!

Are there no witness marks on any of the other bits that run ether side of it, looks like
something may have rubbed it.
Looking again it looks a bit like it as been nipped up between two moving parts.

A worrying turn of events. ?Crank whip/age of seals before fitting/specification of seals/heat etc. Maybe someone at e.g. simplybearings or our old friends could advise on damage cause. Can't help with spec at the moment. Mine have been in 4 years.Roller convertion too.
Will we all be removing our rotors this weekend.....

Hi again does 30407 equal the right crank oil seal spec?

I've looked closer and I'm now pretty convinced that the damage is caused by the dished washer contacting the seal.

The seal which came out was a 30 40 7, and this was supplied by NLM so i'm pretty sure it's correct, however I am going to fit a 30 40 5 which will give a couple of mm clearance, and see how that fares...

Okay so I've now had a better look and I'm afraid it's terminal. Engine rebuild for me this autumn!!

The oil seal itself was more or less completely destroyed, the metal inner was stripped of all rubber and what rubber was left was very brittle. The crank has blued beneath the oil seal, and the oil seal impacted upon the back of the dished belt guide washer:



all that's left of the seal:


Now the telltale sign that means I have to pull the cases- The inner race of the roller bearing has moved ~4mm outwards on the crank, squeezing the gap for the oil seal down from 7mm + clearance to 4.5mm. You can see in the next photo the blued taper on the crank, then the diameter which the seal runs on, and then only a few mm further back the inner bearing race which is as I say a good 4mm out of place:



I'm keeping my fingers crossed that the plugs I put into the crank oil gallery where the bearing journal was are still in place, otherwise I'll have oil starved bigends too...

Could be wrong but it looks like the inner race as spun on the crank, cant see the seal
getting things that hot, does the crank turn ok and feel all right?

Ouf! Sorry to read that it is worse than hoped.

I think Frank might be right about the spun bearing.

I hope you are looking forward to a project for the winter!