[Fot] sealing TR4 rear main cap

[Tony Drews]

To be clear, it's drill two holes, one on either side of the vent tube...

Tony

At 04:28 PM 7/31/2011, Tony Drews wrote:
>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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