[Fot] sealing TR4 rear main cap

Greg Solow gregmogdoc at surfnetusa.com
Sun Jul 31 12:43:36 MDT 2011


First you need to determine exactly where the leakage is coming from by 
close examination of the back of the engine and the flywheel. is the leakage 
out of the seal itself onto the flywheel and then covering the front face of 
the flywheel? Is the leakage from the sides of the main cap where it meets 
the block?
    For years we have used "silicone sealer" along with the felt packing on 
the sides of the main cap. We cut the packing into pieces about 3/8" long. 
During the packing process we look for the sealer to come out in a solid 
line beginning at the very bottom corner (as the block is upside down) and 
continuing all the way up to the pan gasket surface. Then we wipe off the 
excess.
    As for the seal itself. I would get a round piece of stock the same size 
as the seal surface on your crank. Fit the seal around that surface with the 
spring in place on the seal. hold the seal in one hand and look at the way 
it fits against the metal surface. Is the sealing lip deflected (it should 
be), you should be able to move the seal radially from side to side up to 
almost 1/8"  and not see light anywhere around the seal lip where it fits 
against the "dummy crank".
    Lastly, it is imperative that the aluminum seal holder halves fit 
tightly against one another while at the same time not holding the rear main 
cap up from seating firmly against the block!  We have seen this situation 
where the cap will not seat all the way down against the block because the 
seal holder is mismachined and when it is bolted to the block and cap, the 
holder faces touch before the cap will touch the block. The center of the 
seal holder must also be nearly perfectly centered on the crankshaft. You 
must use a centering tool of some kind to make sure this is so.
    If you get all of this right, the seal should only leak a tiny bit. We 
have never been able to make this type of seal completely dry as we have our 
Chrysler seal conversion. But without building the size of the crank back up 
you are stuck with the seal you are tying to use.
                                                                             
                        Greg Solow 



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