i use permatex aviation forn-a-gasket sealant item number 80017. soak the felt
strips for a few days. make sure the mains are align- honed in the block and
double check the crank, and alum seal dimensions.
Steve
On Jul 31, 2011, at 6:23 AM, "J.C. Hassall" <jhassall@blacksburg.net 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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