I had a look on the property of shellac. It does melt at about 1300C and
does not resist to water and some other chemicals. Engine oil was not
mentioned but as it can be solute in ethanol.
I think that is not a proper sealant for engines.
Cheers
Chris
-----Urspr|ngliche Nachricht-----
Von: fot-bounces@autox.team.net [mailto:fot-bounces@autox.team.net] Im
Auftrag von J.C. Hassall
Gesendet: Sonntag, 31. Juli 2011 15:24
An: fot
Betreff: [Fot] sealing TR4 rear main cap
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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