Mike, I would suspect that your head gasket is leaking at the #2, causing high
combustion pressures, which are beating up the bearings, leading to the
failures. The steel shim head gasket is difficult to get to seal. What are
you doing to seal it? Copper coat or aluminum paint are not enough. I put
copper wire o-rings in the fire rings and thinner copper wire around the
lifter valleys. Before I started doing that I was often having head gasket
problems and once bent the # 2 rod.
210 deg water temp seems very high to me. My TR3 runs 195 deg even on hot
(northeast summer) days (with 13.5 compression and a 7300 rpm rev limiter).
Perhaps the spike was the gasket letting go before all hell broke loose? Was
there much water in the oil?
How much clearance do you run between the pistons and the head? With a stock
crank you need at least 0.030 inch. The crank does lots of flexing.
Any cylinder wall scoring? What pistons and clearances are you running?
That's my 2 cents. Joe(B)
---------- Original Message ----------
From: Mike Mehl <mike.mehl@yahoo.com>
To: Triumph Friends of <fot@autox.team.net>
Subject: [Fot] TR4 continued race motor problems spun # 2 rod bearing again -
input thoughts needed
Date: Tue, 19 Oct 2010 10:34:18 -0700 (PDT)
Well -several of you are up to speed on my engine saga. First it was the
head
(May), then the # 2 rod bearing (July 4th Pacific Northwest Historic's) and
then
new engine #2 and then # 2 rod bearing again (Columbia Classic in Portland).
My
understanding that bottom end problems are not normally this bad.
So what changed.
- #2 engine had a different engine builder do the engine. He is very
experienced and does at least one other FOT member engine. He had 15 engines
in
the SCCA runoffs. They know what they are doing.
- The #2 engine had a new crank and all new forged rods. The engine was
running
warm around 210F pretty consistently through all 4 sessions the engine ran an
spiked up to 270 in a big hurry and that was it.
- The engine is equipped with an Accusump.
- The engine is apart and there is nothing obvious that is wrong with the
block. Is there something weird they need to look for?
- The crank was not Nitrited (would that have made a difference this quickly)
Is there something we are missing? I ran the engine between 5000 and 6000
RPM.
It had a 455 rear end gear so I was painfully slow down the straights at PIR.
Could stroking the engine at those RPMs have hammered the bearings? Would
it
happen after a total of 90 minutes of run time?
In the mean time I have crank #3 on the way.
Any thoughts would be much appreciated.
Mike Mehl 62 Triumph TR4 - Vancouver Washington
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