[T3] Number 4 issues..

[Frank Meek <ftalker@hotmail.com>]

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> Worn case:  line-bored cases don't last like a new one;
> Compression too high (<7.5:1) either this time or in this case's earlier 
> life;
> 90's are risky in anything but a Bug;
> What oil wt was in use?
> Did you ever monitor the oil temp?
In response:
It might have been a case failure, but I don't believe so.  The 
compression was 7.65.1, the oil was 20/50 summer, 10/40 winter.  The oil 
temp and cylinder temps were under constant surveillance.  Indeed, the 
oil was referenced on a three-way switch at three places: the engine 
core, via dipstick sender, at the oil passage in the outflow to the 
external cooler and at the return passage from the cooler.  I monitored 
relative  oil temps, oil pressure, cyl temp and EGT. The temps were out 
of specs only at the moments  of failure, the oil pressure, however had 
declined, as I indicated, over some period.  This, then, indicates to me 
that the number four bearing started to dissolve many miles (about 5K) 
before imploding.  In the future, I shall stop operation at any time the 
oil pressure declines continually out of the "norm" for my rebuild.  
This oversight cost me a crank, case and time.
In terms of the 90's being a poor choice for the T-3's, that is indeed 
the party line from Gene Berg and company.  However, my experience has 
not upheld this myth.  I ran 5-10 degrees hotter with the 90's in the 
mountains and that was roughly 190-220F, summers, well within specs.
Also, in answer to the "sludge" theory, while that may well be the 
reason for failures, it is not my reason.  I run only filtered oil and 
change this within 3K and I changed the strainer every other oil 
change...even though I NEVER saw any evidence of particulates or sludge 
on the screen or plate.
I believe that there is another reason for these seemingly regular 
reports of number four failures from different folks, places and engine 
setups.  But, I do not have the answer...yet.  I suspect it may be 
somewhere in the unique nature of the T-3 as a transition between the 
historically rugged upright and the very successfully engineered T-4.  
The airflow comes to mind as do other elements of the cooling systems.  
I will persist. 
Obviously, this forum is ideal to help formulate and resolve these 
shortcomings.

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