Rear main Scroll Seal

I'm in the process of engine reassembly on my 4. I have a question for those possibly knowledgeable on the subject on the rear Scroll seal. Despite recommendation to go to the newer style seal I decided to keep it as is since my crank was in no need of a grind on the journals..knowing it will leak somewhat as original. My question is: why can't I loose fit the new scroll seal halves on the block and rear bearing cap and then use the crank w/ main bearings in place and tightened to align the scroll seals? Instead of using the " $50 alignment Tool"? It seems to me this would be a better way to align the seals. Also, Q#2: the Bentley manual says to use "Jointing compound on the contacting faces" - Does this mean the contacting faces of the Seal Halves? or on the faces of the halves to the Block and Bearing Cap? Thanks for any advice.

MrAlex said:

My question is: why can't I loose fit the new scroll seal halves on the block and rear bearing cap and then use the crank w/ main bearings in place and tightened to align the scroll seals?

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Because the crank won't be centered in it's running clearance, and there won't be any clearance between the seal and crank. As soon as you start the engine, the crank will tear into the seal, likely ruining both of them.

Actually, it can be done, by adding shims to correct those two problems. An old time TR3 racer once told me he did it using sewing thread wrapped around both the main journal and the scroll; but I've not tried it myself.
<div class="ubbcode-block"><div class="ubbcode-header">Quote:] Instead of using the " $50 alignment Tool"?[/QUOTE]From what I've been told by those who should know, the "$50 alignment tool" is worthless and results in too much clearance. Supposedly even the dimensions given in the shop manual are too big, and the tool is bigger yet.<div class="ubbcode-block"><div class="ubbcode-header">Quote:]Also, Q#2: the Bentley manual says to use "Jointing compound on the contacting faces" - Does this mean the contacting faces of the Seal Halves? or on the faces of the halves to the Block and Bearing Cap?[/QUOTE]In a word, Yes. Both places.

Thanks for the reply. Since I am going with the Scroll.. it seems I need to provide an adequate clearance gap. I was thinking a layer of grease (assembly or molly lube) or even a layer of teflon tape might provide adequate clearance rather than thread which I think would be inconsistent in the scroll threads. What other options or alternatives have others used for this?

TR3driver said:

From what I've been told by those who should know, the "$50 alignment tool" is worthless and results in too much clearance. Supposedly even the dimensions given in the shop manual are too big, and the tool is bigger yet.

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I borrowed one of those alignment tools from one of the guys in the Triumph club, and is WAS about .003"-.004" larger then the dimensions in the factory manual. My original seals showed no signs of any leakage. Fortunately, I hadn't yet removed them from the block and cap so I was able to take a measurement. Sure enough, as Randall has said, it was a couple of thou smaller then the measurement in the book. I made up a tool with this new measurement. I'll only know how well it worked after I fire the engine up, which won't be for another month or two.

Hi Art.. Would you be interested in Renting out your tool to me? I'm up in Poughkeepsie. Funny.. also my wife will be in Glen Cove today at a Baby Shower if it is possible to arrange something please let me know. Also, if you have the dimentions another option would be to have a friend turn one for me on his lathe. Alex (cell 845-464-0505)

Ah, here it is. One message says the seal clearance (to the scroll on the crank) should be .003" (implying you should measure your crank and make the mandrel .006" larger in that area).

Another says the mandrel should be 2.818" where the workshop manual shows 2.822".

I talked to Alex by phone and would have loaned him the tool I made up, but unfortunately, I loaned it to another club member and he can't seem to find it at the moment...whatever that means. The tool I made measured about 2.8185". I just used a piece of delrin we had at work. No handle...not neccessary. Besides, I had the engine on a stand and the handle would only get in the way. The ones from Moss are made from some sort of hard plastic, but as mentioned above, are oversize.

>The tool I made measured about 2.8185".

Interesting. I made mine back in '82 to 2.819" (I am ashamed to admit I was aiming for 2.822"). I missed the scroll diameter by -3 mil and the hit the crank diameter. Blind Luck.. I used it to put my TR4's main seal in and it doesn't leak any noticeable amount... Wish my TR6 had the same problem.
Tim

I am going to try an experiment by using 1 layer of Teflon Tape (which I measured to be 0.003 in.) on the Crank Scroll with the Scroll seal halves fit loosely and with sealing compound only on the faces of the seals. Then torque down the crank with bearings in place and align/tighten the seal bolts. Then remove the teflon tape.

What are you doing to center the crank in it's bearing clearance ?

I have between 0.0015 and 0.0020 clearance on the rear main bearing using Plastiguage. That is with no Lube taking the measurement. I figured if I do the Rear seal fitting with Assembly Lube in place on the Main Bearing it will take up a portion of the gap. Worst case witht the motor right side up I'll still have clearance on the bottom side. I guess that I could even take some of the gravity weight off the crank to do the seal as well. Tell me if you think I'm nutz (maybe you already did).

Personally, I'd still follow Hardy's advice and wrap the crank journal with thread while setting the seal. I don't think your assembly lube is anywhere near thick enough to carry the weight of the crank without squeezing out. But that's just me, perhaps your method will work fine.

(Actually, I got talked into converting to the lip seal, so I won't have to worry about this particular step )