REFLECTOR: Cylinder repair followup

[John Dibble]

With further investigation of my recent failed cylinder and related
issues, I have concluded that a combination high oil temp and tighter
cylinder clearance is the cause and would like comments on how to
proceed.  First is the oil temp.  My oil temp had been pretty good the
past year or so.  Then 4 months ago I added 3 washers behind the bypass
spring to raise oil pressure.  I didn't notice temperature issues then,
but it was a much cooler time of the year.  As I understand it, the
reason the pressure was low, was due to engine wear which allowed oil to
pass through the lubricating areas more easily.  I suppose if the wear
was uniform, then the lower pressure would not matter, but it's most
likely that some areas didn't wear as much and need the higher pressure
for lubrication.  By raising the pressure with the washers, there is now
more oil being pumped through the engine than before which means more
oil is also going through the cooler.  That explains the higher oil
temps since the available cooling air is unchanged, so the oil can not
be cooled as much as before.
The 3 washers gave about a 10-12 psig increase in pressure.  However,
the higher oil temp eliminates most of that increase ( maybe not really,
since the reason for the decrease in pressure at higher temps is that
the oil flows more easily and good lubrication is still being
achieved?), so I'm thinking of removing some or all of the washers.
What I'm wondering is what is the minimum oil pressure that I can fly
with?
The other issue is cylinder clearance.  I've had 2 PZL sleeves replaced
with American sleeves (I understand that is all that is available).
Each time I sent the cylinders for repair I was told that the PZL liners
were beyond the tolerance.  It seems strange for that to have happened
in as little as 350 hours.  Besides my remaing PZL cylinders have 700
hours and are working fine.  For that matter the 2 PZL liners that were
replaced looked in good condition with no scoring.  I replaced them only
because I was told they were beyond the tolerance limit.  In retrospect,
I think I should not have replaced them as I feel that the new liners
have a too tight tolerance.  The i.d. of the new liners is 4.465" and
the mechanic said I could have them bored out 0.003".  I'm thinking of
doing that as I think I need greater clearance for my operating
conditions.
I suppose I could also install a second oil cooler.  Seems like that
would be more work.  Anyway, I'm looking for suggestions as to which way
to proceed.

Thanks,

John