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RE: TR4 Rear Main Seal

To: <triumphs@autox.team.net>
Subject: RE: TR4 Rear Main Seal
From: "Randall Young" <Ryoung@navcomtech.com>
Date: Mon, 7 Jul 2003 22:08:41 -0700
> Okay what can you very informative folks enlighten my with this subject.
> Awhile back I posted that the little beast was having clutch problems, and
> later to learn that the, and suspected, throw out bearing, shot,
> too.  Anyhow,
> to make a long story short, I took it to a qualified mechanic, to
> take care of
> those problems. He told me he owned a TR, so quite familiar.
> Anyhow, he is
> very paranoid about the replacement of the rear main seal and
> specifically no
> guarantees that it wont leak.

According to people who should know, the setting mandrel is an absolute
necessity, and the dimensions shown in the factory manual for it are wrong.
The dimension that is shown as 2.822" should actually be 2.818".  The
factory tools were the smaller size, but it's been reported that the
replicas sold by Moss are even bigger than the (incorrect) larger size.

Another problem is worn engines that have enough blow-by to develop pressure
in the crankcase.  The factory seal will not resist any pressure at all.
The only cure is to fix the blow-by (although converting to a TR3-style road
draft tube might help as a band-aid).

There have also been reports of poorly made seals, with too large a radius
next to the corner of the block.  Check carefully that the seal lays flat
against the block and doesn't rock against the corner.  The easiest fix is
to radius the block a bit with a round file.

One last thing, in case you're tempted by the "high tech" seal conversion :
double check the correct diameter before having the crank ground down.
Apparently some vendors (Moss) were at one time telling people to grind to
63mm.  The correct dimension is 2.500"  The difference is only .020" or so,
but it does make a difference.

Hope this helps.
Randall

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