I sent this to Alex yesterday and forgot to CC the list:
There is no real seal as you point out. Oil oozing out of the rear main
bearings is supposed to go into the machined trough that appears just before
the 'scroll seal" area of the rear main cap and the half moon piece with the
three bolts that attaches to the back of the block. Once the oil goes into
the trough it is supposed to drain back into the pan through two holes in
the bottom of the groove in the rear main cap. The 'seal' function is
supposed to be provided by the closely machined match of a flat surface
presented by the aft part of the main cap and the three bolt piece. This
flat area serves as the aft wall for the oil capture/drain trough. The
matching area of the crank has a small helical groove machined into it that
is supposed to pull any escaping oil back toward the trough to drain back
into the pan. Excessive backpressure in the block is usually the cause of
this system failing and dripping as the oil is blown past the above
described bits. A true lip seal will not cure the backpressure problem.
Paul A. of this list has a simple kit to restore the close fit in the scroll
area to better-than-new tolerance. A drill press is handy to do the job
necessary for the kit.
I used his kit to tighten up the clearance, and then cured the root cause of
my
engine's backpressure problem (cracked pistons). As a result, my driveway
and garage are free
of new spots. If this is enough to make a leak-free motor out of my .030
overbore/turbocharged unit, it should work for you. I do not have any
added breathing ports or a PCV. I'm running only the vented valve cover cap
and the timing chain cannister with a "road tube" as Gerard describes. I
did remove the steel wool filler from the cannister on the timing cover.
The 1380's are apparently a whole different story for their own unique
reasons(bore-flex).
One thing to consider is that the sudden onset of leakage at the real seal
is diagnostic of a change within the motor that needs attention. In any
case, Paul's kit makes good sense as the tightest possible clearance at this
"seal" is a GOOD thing.
Regards,
Glen Byrns
'59 bugeye
'59 Morris Traveller (Winifred)
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