The crank thrust washers on a Triumph engine leave a lot to be desired.
You're right in that the rear main bearing car is supposed to hold the two
thrust washers in place. If the rear one should drop out (not uncommon) then
the crankshaft wears the main bearing cap, at the same time as damaging the
cap (so it's no longer wide enough to hold the thrusts in place) it also
damages the face of the crank that the thrust washer runs against. As a
minimum the crank thrust faces have to be ground smooth (as material is
removed oversize thrust washers must then be fitted), and the main bearing
cap repaired so it holds the thrusts in place. But this repair can be done
with virtually any sort of welder and grinder/files as the tolerances
aren't critical, then it is a matter of putting it all back together with
thicker, decent quality, thrusts. There are a number of other repairs which
may be superior but tend to be a lot more expensive. So, it's engine out,
crank out, grind crank thrusts, repair main bearing cap, reassemble, refit
engine. New thrusts fitted without regrinding the crank will last a few
miles, main bearing caps can't be interchanged without having the block line
bored.
John Kipping
----- Original Message -----
From: "Scott Janzen" <s.janzen@comcast.net>
To: <fot@autox.team.net>
Sent: Tuesday, June 01, 2004 3:50 AM
Subject: #4 Main thrust Bearing Question
> I pulled the pan off of the engine to replace a leaky pan gasket. Found
> nasty looking metal chips that appeared to be a thrust bearing. Now I'm
> looking at the main bearing cap on the engine. It has a groove on the
> flywheel side that would appear to accept a thrust bearing. The manual
only
> seems to show thrust bearings in the block., not one on the flywheel side
of
> the cap as well, and there was only a bearing installed in the block. It
is
> also clear that the bearing has been rotating through the cap (cap's all
> scored in this groove). Now, I pull the bearing cap off of a spare engine.
> No groove for a thrust washer, so the cap keeps the bearing from rotating,
> and the bearings in the block take all the thrust.
> Which is correct? Did Triumph change things along the way? Can I switch
> bearing caps between engines, or was the cap machined in place?
> Fortunately, the crank bearing surfaces (all three of them) look fine, as
> does the journal bearing.
>
> Help! Thought I would be putting the engine back in the car today, but it
> does not look good at the moment.
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