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TR2/3/3A rear main seal

sp53

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I am trying to understand why the centering of the mandrel is so critical when installing a rear main seal on a Tr3. The rear main cap is pulled down tight and the oil scroll is going to throw the oil back into the engine once the RPM rise. I see how the rear seal on the cap lets the oil flow back into the pan, but that ultra-precision of the centering seems not too critical to me. The holes in the aluminum piece are not slotted, so how do I move it much anyway. I know I am not the sharpest tool in the shed, but understanding helps me. Anyways, I will most likely purchase one of Mad Max’s seals, but if I do not need the centering tool why buy it. I am still waiting for Art’s stock rear main to leak, but perhaps he is out of oil and does not know it. The last one I did leaked badly. Using too much Indian Head gasket sealer might have contributed to rear main leaking on mine because I fear the small hole feeding the oil back might have become partially plugged. I see one of Mad Max’s seals for sale EBay and I see that TRF has them. If I buy from the TRF, I will get their warranty on parts, so that seems the way to go.
 

GerryL

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The one advertised on ebay is provided by Joe Alexander, who supplies TRF. I purchased it thru ebay and he was helpful in answering any questions that I had in regards to installation. The seal has worked and so far haven't had any drips.
 

CJD

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To be honest, I had never heard of a "scroll seal" till I bought my TR3. With an engineering background, I naturally studied it intensely when I had the part off. As far as I am concerned, it is ingenious! It will never be absolutely dry, but on the other hand it also will never wear out or score the crank. I left it in when I reassembled, and have never regretted it.

The reason for the setting mandrel is that you are dealing with extremely tight clearances. If the2 scrolls do not lineup absolutely perfectly, you will lose oil, and possible cause one scroll to contact the crank...and lose oil. Setting the mandrel is the only downside with the original seal, in my opinion! But once done, forget about it for the life of the engine.
 

tinman58

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I am like you. I want to understand why things work. Even thou the machined parts are not slotted, there is still some wiggle room. What I have learned is do it as the instructions say. It will eventually make sense. Make sure you check the length of the flywheel bolts. They tend to be a little long and can rub against the new seal, causing a very nice oil leak..... believe me I know....
 

TR3driver

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The one advertised on ebay is provided by Joe Alexander, who supplies TRF. I purchased it thru ebay and he was helpful in answering any questions that I had in regards to installation. The seal has worked and so far haven't had any drips.
Joe also supplies to TRF. He is the only authorized importer in the US.

As noted, the clearance between the scroll part of the seal and the crankshaft is critical to the operation of the scroll seal. It is probably less critical when combined with the Viton seal, as it's a "belt and suspenders" arrangement; but you still don't want to have the aluminum seal touching the steel crank when it is assembled.

If you really, really don't want to buy (or make) a mandrel; I have heard tales of wrapping the crank journals with fine thread and using it as a mandrel. Hardy swears it worked for him (with the factory seal, back when). But if you are going to spend all that money on an improved seal, why not install it as the maker recommends?
 

Got_All_4

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I have my engine out only to repaint the engine compartment. Although driving the car for 30 years I've had minimal problems with oil leaks but have been thinking of doing a conversion. One question first is how does the flywheel flange come off the crank? For a modern oil seal to work it will have to come off.
 

tinman58

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The viton seal is split. the seam goes up towards the head when installed.
 

TR3driver

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Right. So is the other conversion. The flange doesn't come off.
 

martx-5

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... I am still waiting for Art’s stock rear main to leak, but perhaps he is out of oil and does not know it...

I see you've discovered my secret...no oil...

Actually, I think that most of these leaks from the original scroll seal are due to the fact that the dimension given in the workshop manual is incorrect. They show the dimension as 2.822" when it should be 2.818". To make matters worse, the tools that Moss was supplying measured 2.825". I don't know if Moss has gotten that straightened out, but any centering tool that you use should be measured carefully.
 

TR3driver

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Actually, I think that most of these leaks from the original scroll seal are due to the fact that the dimension given in the workshop manual is incorrect. They show the dimension as 2.822" when it should be 2.818".
Another reason, I believe, is that it is difficult to assess wear on the seal and so many people reuse them when they shouldn't. Of course it is non-contact by design, but with worn main bearings and hard driving, the crank can contact the seal and wear away a bit. Only takes a few thousandths to make it leak badly.

Yet another reason (which mostly affects only later TR4 and 4A) is pressure buildup in the crankcase. Full throttle is when there is the most blow-by past the rings; and yet at full throttle there is no intake manifold vacuum to pull fumes past the PCV valve. The result is a momentary build up of pressure inside the crankcase, that overcomes the surface tension of the oil in the gap of the seal and blows it out. (TR4 didn't use the valve, but the small tube to the air filters can also allow pressure to build.)
 
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