Be CERTAIN you replace the bearing shells with the same size as the ones
presently installed. The bearings do not wear evenly and develop an oval, not
round opening. This may seem obvious, but only to people more
intelligent/experienced than I.
In 1988 I installed new bearing shells in my rather worn engine while far from
home. I had already done this before starting my trip to my mother's cottage
for some home-cooked food. I was somewhat disappointed at how the new shells
had only lasted about 500 miles or so before starting to knock again. Being an
insane optimist I thought "Oh ho, look how loose these bearings are already,
the crankshaft must be worn down. I will install the next oversize to take up
the slack." Thus, after lying under the car trying to polish off the ridges on
the crankshaft bearing surfaces with emery paper to make the surface round,
(There are times when one wonders what sort of deluded thought process was
working prior to that sort of error) I installed the next size up and started
the engine. All the knocking was gone. I felt so cheerful. So I took off to
drive the 400 miles home.
About 15 miles later on steep hills I suddenly heard a terrible banging and
clattering followed by silence except the car was now running on 5 cylinders.
Mystified, I stopped at the bottom of a steep hill then jacked up the nose and
crawled under to remove the oil pan suspecting I had had a bearing bolt come
undone. Having removed the pan I was astounded to look up at the bottom of
the engine and see a clear blue patch of sky shining thorugh the block!
Suspecting that this was not normal I investigated further. I discovered that
the #3 big-end bearing had seized and, spinning the connecting rod, punched a
hole in the side of the engine and then dumped the bits of piston and rather
bent up rod in the pan. You know, when you are out of work, nearly dead bust
and lying on your back in the dirt looking at a sight like that you really can
feel low.
But never ever count a Triumph out! Amazingly the hole (the size of a golf
ball) had not affected the oil pressure or coolant. So, figuring I had little
to lose, I put back the pan, poured in some oil and drove back up airport road
(very steep and hilly) to my Mom's place. The Triumph didn't much like those
hills on 5 cylinders, but it kept on going. A bit unbalanced with no rod or
piston on #3, but no smoke. JBweld, Ha! I blocked that hole with a rag and
some electrical tape to keep the oil in. I have heard all sorts of moaning
about design issues and desired optimisations, but in my humble opinion, those
TR engines are tough!
That was the start of 10 years (really going on 16 now) of rebuilding. By the
way, I later had that block re-welded and it is still the one in the car. Try
that with a new engine design and see what happens.
Mark
1972 TR6
________________________________
From: owner-triumphs@autox.team.net on behalf of Dave1massey@cs.com
Sent: Sun 22/10/2006 8:07 PM
To: jmitch@snet.net; 6pack@autox.team.net; triumphs@autox.team.net
Subject: Re: [TR] Engine knock
In a message dated 10/20/2006 8:24:49 PM Central Standard Time,
jmitch@snet.net writes:
> Am I correct in that I can change the bearings
> without removing the crankshaft? I'm at least happy that's it's not
> camshaft in the oil
Yes you can. I did that and a new oil pump a few years back and oil pressure
improved significantly. Be sure to losen the fan belt or #1 main will be a
bear.
Dave
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