[Fot] sealing TR4 rear main cap

[Tony Drews]

Your assembly sounds exactly like mine, and I got it to not leak very 
much this year.  The one change I made (due to a dialog on this forum 
a while back) is to:
1. Make sure that the vent tube that goes through the rear main from 
the rear seal to below the crank is open.
2. Drill two extra 3/8" holes in the rear main cap parallel to the 
built in vent tube on either side of the vent tube.  If you don't 
give the oil any place to go, it will go out the rear main no matter 
HOW good the seal is.

I suspect the above is your issue - you can get a little oil through 
the vent tube (works on the starter) but not a lot of oil through the 
vent tube (doesn't work when engine is running).

The Indian Head Shellac has worked fine for me (and for Uncle Jack) 
for years - that's not your problem.  I do not soak the felt for more 
than a few seconds.  It does come out both sides of the gap between 
the main and the block and is messy.

Also, make sure that you're not really leaking from somewhere else 
like the cam plug or the end of the main oil gallery.  Both of those 
will fill up your bellhousing in no time.

Tony Drews

At 08:23 AM 7/31/2011, J.C. Hassall wrote:
>Haaaaaalp!  I'm at my wit's end.  The rear main cap is still leaking 
>("pouring"?).  In the course of maybe 20 minutes run time it dumped 
>~1/2cup of oil and some drips of sealing shellac.
>
>History:   This will be the third attempt to seal the leak.  I'm 
>using the split seal kit with the incorrect crank dimensions.  On 
>the initial build I shortened the spring to 8 3/8" per a phonecon 
>with Uncle Jack. I packed the grooves in the cap with 1" pieces of 
>felt soaked in Indian Head Gasket Shellac and pounded the life out 
>of them.  Each side took 7 1" pieces.  Some shellac oozed into the 
>block and also on the outside.
>I cleaned up the inside with lacquer thinner (carefully, to not thin 
>the shellac in the cap).  I put a very thin film of RTV inside the 
>seal housing and on the block to housing interface.  All seemed good 
>with the world until it dumped LOTS of oil, leading to the current 
>rebuild.  Some shellac also dripped from the back of the block down 
>the inspection plate.
>
>This time I shortened the spring to 8" and trimmed an RCH from the 
>end of the seal, ensuring that the ends were parallel and had no gaps, etc.
>Same assembly technique for the cap and seal housing, but with more 
>RTV on the seal housing.  I soaked the felt strips in the same 
>Indian Head and pounded them home again.  I made a special punch 
>which conformed to the cap groove contours, to ensure that the felt 
>was pounded uniformly.
>Shellac oozed into / out of the block as before.  Shellac also 
>dripped from the hot engine, but only in a few thin threads, not the 
>thick beads as the last time.
>
>Before firing the engine this time I cranked it with the starter for 
>3 sessions of 2 minutes each (best run-time simulation I could think 
>of), with no leaks.  I haven't torn down the engine yet (this last 
>leak occurred last night).  Clearly I'm doing something wrong, but 
>have no idea what.  HAAAAAAAAAAAALP!  My suspicion is that hot oil 
>thins the shellac and it pours past the felt strips.
>
>TIA
>
>jim
>
>--
>Jim Hassall
>Blacksburg VA
>'63 TR4 in autox preparation
>99% finished, 90% to go
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