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[Fot] sealing TR4 rear main cap

To: fot <fot@autox.team.net>
Subject: [Fot] sealing TR4 rear main cap
From: "J.C. Hassall" <jhassall@blacksburg.net>
Date: Sun, 31 Jul 2011 09:23:33 -0400
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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