I run 0.0027 for the mains because of crank flexing.
The good thing with the smaller rod bearing clearance is that you don't need
much oil to lube them.
I found that with the stock suggested clearance the rod bearings started to
get thirsty at revs beyond 4000.
I found the oil pressure dropped from 90 to 70 PSI at 6000 rpm.
With that small clearance the pressure remained at 90-95 even at hot days.
And after a race I have 50-60 PSI at idle speed (1300 rpm).
Cheers
Chris
-----Urspr|ngliche Nachricht-----
Von: Jim Gray [mailto:toodamnfunky@comcast.net]
Gesendet: Mittwoch, 20. Oktober 2010 02:52
An: 'MadMarx'
Betreff: RE: [Fot] TR4 continued race motor problems spun # 2 rod bearing
again - input thoughts needed
Chris,
What kind of clearance do you use at the main bearings ?
Thanks,
Jim Gray # 102
-----Original Message-----
From: fot-bounces@autox.team.net [mailto:fot-bounces@autox.team.net] On
Behalf Of MadMarx
Sent: Tuesday, October 19, 2010 3:00 PM
To: 'Triumph Friends of'
Subject: Re: [Fot] TR4 continued race motor problems spun # 2 rod bearing
again - input thoughts needed
What bearing clearance do you run?
I went down with the clearance a lot and found the rod bearings much more
happy with it.
Over the year I ran 0.00275 as clearance but found wear on the bearings.
This year I ran 0.00118 and I had a huge oil pressure and almost no bearing
wear.
I kept the old bearings for good as they are looking as new.
Chris
-----Urspr|ngliche Nachricht-----
Von: fot-bounces@autox.team.net [mailto:fot-bounces@autox.team.net] Im
Auftrag von Mike Mehl
Gesendet: Dienstag, 19. Oktober 2010 19:34
An: Triumph Friends of
Betreff: [Fot] TR4 continued race motor problems spun # 2 rod bearing again
- input thoughts needed
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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