I have finally achieved success (after 6 attempts and 2 different engines) with the Chevy rear seal on my XPAG that Andy Bradley designed. Upon suggestions from Andy Bradley, Mike Goodman, Bill Traill, Ben Prince and a few others, I (at least so far) have a non leaking TC.
As I tried several things on the last attempt I am unsure as to what caused the leaks before, but here are my theories as to why I was unsuccessful and hopefully will save others from making similar mistakes.
I believe my previous leaks came from one, or a combination, of four
different places.
1. From between the aluminum piece and the block
2. From the end joints of the seals where they meet each other
3. From between the aluminum piece and the cap
4. Use of the drain tube
When tightening up the aluminum piece it is quite easy to distort it. Areas around the bolts will seal but there could be large gaps in between and at the ends. I tried to be careful in applying the silicone (use no gasket) as the instructions indicate to avoid it squeezing out. In my last assembly, as the piece was already distorted, I applied a tad bit more than I usually had and held it up to the block and pulled it back off. There was still one area where was not sealing as there was no transfer. I applied more and let it squeeze out just a tad.
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Aluminum piece showing distortion. It is resting on a mirror so the gap may appear larger than it is. This is the actual piece I used on the last installation. A distorted piece is not necessarily trash. |
On one of the seals I pulled out, I noticed that when holding the 2 halves together that there was a gap between the ends visible to the eye. Squeezing it tighter reduced the gap slightly but it was still visible to the eye. Embedded in the seal are metal "U" channels. The metal was hitting and not allowing the flexible part of the seal to mate. The last seal I bought seemed to mate better but as a precaution I applied a small smear of Permatex Hylomar HPF gasket dressing (non hardening/non curing) at the ends of the seals where they meet. As an added precaution I rotated the seal so the seal ends mated at a position other than where the cap and aluminum piece meet. The theory is if any distortion occurred with the aluminum piece to where the aluminum piece and the cap don't line up exactly right, the seal lips would also be off. The ends may look right on to the eye but a very small misalignment could cause the lips to not line up. Rotating the seal insures the lips line up.
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This shows how I rotated the seal so the splits don't line up . Hopefully it assures that the seal lips line up. Notice the removal of the drain tube. |
Now the aluminum piece is only about 3/32" thick where it meets the cap. We are relying on sealant in this thin section to hold back the oil. Add to this any misalignment and the sealing surface is reduced even more. In order to improve my odds I filled the channel in the aluminum piece in with JB Weld near the ends. This more than doubled the contact area and provided a much larger sealing surface.
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The aluminum piece is less than 3/32" at the thin spot and when warped it rode off the cap a bit too. Red outline shows where aluminum piece sits. Red shading shows where I filled in with JB Weld. Also notice the metal "U" channel embedded in the seal. There is a possibility that it can hold the seal apart causing a gap. Suggest not trimming metal but to use the Hylomar sealant on the ends. |
Andy Bradley suggested removing the drain tube in the cap. It is unclear to me why this would cause a leak but Andy indicated that the conversions he heard about leaking, all had kept the down tube. Before removal, I had cut a wedge shaped hole in the tube about half way up facing the front of the engine. This insured the oil would not back up in the tube and would flow out there if needed.
I would like to mention a few other items. One is the offset seal.
Depending on how the welder built up the journal on the crank, it may
or may not go all the way to the flange. The drawing provided by Andy
Bradley does not specify how far back the new journal must go. If the
welding goes all the way to the flange you can use a regular seal. This
may cause the flywheel bolts to bottom out and cause the flywheel to
be loose. Shorten the bolts if necessary.
If however the weld falls short of the flange as the drawing depicts
the regular seal may not fully ride on the journal. The second lip (just
to keep dust out) will not ride off the edge and become ineffective.
The oil seal will still seal very nicely though. To get the dust lip
on, you can buy an offset seal that shifts both lips back and solves
the problem (Victor Reinz part number JV1627).
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Top shows first seal used. Double lip, but dust seal rides off journal.
Bottom shows offset double lip seal. Both lips ride on journal now. My other engine has the weld going right up to the flange and both lips ride on journal with a regular double lip seal. |
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There are other areas in the back that can cause leaks (cam core plug, oil gallery plug, pan gasket and cork seal to mention a few) but the four I explained above is where I believe my problem was.