I thought I'd chime in on this rear seal thing with something that won't apply
to 99% of you...
I found the rear seal on the TR 4A to be extremely susceptible to crankcase
pressures because of the closed system breathing. As you all know, the lower
breather hole was blocked and the valve cover has a sealed cap with only a
small tube out the side to breath.
Unblocking the lower engine breathing hole and allowing the valve cover to
breath more can do wonders to alleviate rear seal leakage. As an example,
when I first bought my current TR 4A, the engine, that had sat for 20 years,
could be made to run, but the oil out the rear was a constant flow... Popping
out this plug turned it from a stream, to a drip. Of course, that engine
had terrible blow-by from worn out rings, however, I've also seen drips
become less serious, by opening things up on a rebuilt motor, both on my
current 4A and my previous 4A.
I said this wouldn't apply to most of you, because only so many of you have
4A's, and most of you would have already opened up the engine to breath long
ago. However, some of you may race another TR, but have a 4A in the
driveway... Or perhaps you're just getting started, etc.
Warning here. If you still have that plug in your TR, and you're thinking of
removing it, keep in mind that it's easy to pop out when the engine is out of
the bay, but it can be a nightmare otherwise. Don't start to remove it with
the engine installed unless you're prepared to pull the motor if you fail.
The interesting thing here is that letting the valve cover breath isn't
enough. So even though air/pressure can travel down through the push rod
tubes and beyond, it doesn't seem to provide enough flow. That's just my
experience. And obviously they felt that way at the factory, since they
installed that huge breathing tube in the earlier engines despite having a
fully breathing valve cover cap. Subsequently, on a TR4A, just venting the
little smog tube out the side isn't really enough. It could really use more.
My TR 4A does leak out the rear, but it takes a long time to lose a quart.
(And, of course, my valve cover doesn't leak a drop. : )
--Justin Wagner
jmwagnersales.com
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