On Sun, 1 Oct 1995, F. van Dalen wrote:
> > That's why the XPAG/XPEG engines in the T-Types have a
> > drain hole at the lowest point of the flywheel housing, complete with
> > loose split pin to rattle around and keep dirt from clogging the hole.
>
> My '69 B has that! I'm stunned to learn there is actually a use for that crazy
> split pin. Would idling the engine for a while on the B help in keeping my
> dad's driveway clean?
It's worth a try. You can test the before and after results via the
high-tech "puddle on the paper" method I mentioned in my earlier message.
Keep in mind, though, that the condition of the rear main bearing has a
lot to do with it. If you've got too much clearance at the rear main,
through wear or through the "grind 'er a bit more, Alf, just to be safe"
approach taken by many crank grinders, then you are going to get some
leakage past the rear main "seal" no matter what you do because the oil
leakage out of the bearing becomes greater than the slinger and return
thread "seal" can contain.
I don't know if this applies to the MGA and early MGB too, but on the
XPAG/XPEG T-Type engines the cavity surrounding the slinger is formed in
the block and in the rear main bearing cap. The rear of the block half of
the cavity is sealed by a pot metal cap bolted to the back of the block.
When it is in place, it is supposed to mate tightly to the bearing cap,
and at the same time provide a small but uniform clearance around the oil
return threads behind the slinger on the crank.
Some of the replacements manufactured since the original MOWOG part became
unavailable haven't fit very well. Quite often if you adjust it to seal
tightly the gap between it and the bearing cap, there is zero clearance
opr even outright interference between the slinger cap and the threads on
the crank. This causes the threads to grind into the cap, which is no
great loss, but the main problem here is that it forces the rear main
journal hard against the lower half of its bearing, causing premature wear.
Or, if you adjust it to provide adequate clearance around the threads, a
big gap is left between the slinger cap and the bearing cap. This leaves
the slinger cavity open to the flywheel housing, which then receives a
lot of oil through the gap.
Every engine builder has his/her preferred way of dealing with this.
Some adjust the slinger cap to provide clearance around the oil return
threads, then seal the gap between the slinger cap and the bearing cap
with high-temp silicone sealant. This is quick, easy, and usually works
as long as you don't get the sealant on the oil return threads and as
long as the sealant stays in place.
The approach I like is to install the slinger cap loosely, torque down the
bearing cap, push the slinger cap hard against the bearing cap, then
tighten it down. Remove the bearing cap. Apply bluing to the radius of
the slinger cap. Install all three main bearings and torque down the caps
to seat them. Remove the bearing caps, oil the top bearing halves, and
drop the crank into them. Rotate the crank a bit, then remove it. If the
bluing is scraped off part of the radius of the slinger cap, relieve that
area with a scraper. Repeat until bluing is no longer removed when you
rotate the crank. Re-blue the cap, install the crank, torque down all
three bearing caps, turn the crank, take it out, and see if any bluing
has been removed. Often the cap clearance will tighten up again when you
torque down the caps, so you need to check it under those conditions
too. For the final assembly, clean the mating surfaces between the
slinger cap and the bearing cap and put a thin smear of silocone sealant
on them before installing the bearing cap.
Another approach used by some is to install the slinger cap so it mates
tightly with the bearing cap, install the crank, and keep turning it
until the oil return threads stop grinding into the slinger cap. Ouch!
Another source of oil leakage into the flywheel housing (in the
XPAG/XPEG, at least) is the "core plug" that seals the rear of the
camshaft bore in the block. If that isn't installed properly, oil from
the rear camshaft bearing leaks into the flywheel housing.
Yet another source of leakage into the flywheel housing is the threaded
plug at the rear of the main oil gallery bore. This should get a liberal
dose of thread-locking compound when you install it! If it loosens up
you will get a massive high-pressure oil leak into the flywheel housing.
And you wondered why there is a drain hole at the bottom of the flywheel
housing!
-----------------------------------------------------------------------
Chip Old 1948 M.G. TC TC6710 NEMGTR #2271
Cub Hill, Maryland 1962 Triumph TR4 CT3154LO (daily driver)
fold@mail.bcpl.lib.md.us
If cars had evolved as fast as computers have, by now they'd cost a
quarter, run for a year on a half-gallon of gas, and explode once a day.
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