Well, -=MY=- theory on what causes numerous 2.7L lower end failures seems to be 
holding up on my end here.  I got it out of the car and on the stand.  This is 
the story:
 
Now, my theory is that the timing chain tensioner O-rings tend to fail (I've 
seen two cases in the past), resulting in two things:  A loose and rattling 
timing chain and oil pressure loss.  A loose timing chain is harmless 
short-term such as after changing oil and initial startup, but the long term 
effects will make the chain slap the guides breaking them up and/or timing 
chain failure/skip and Mr. Piston meets Mr. Valve and the party is all over 
with.
IF the timing chain and related components hold up, its going to cause a loss 
of oil pressure while warm and at low RPM's.  Loss of oil pressure is not a 
good thing for the lower end bearings.
 
During my teardown, I find no sludging.  Internal cleanliness is good.  The oil 
pan was somewhat dirty, but not bad by any means for any 95,000 mile engine.  
Guess what I find in the oil pump pickup screen?  The failed tensioner O-ring 
in 3 pieces and a bunch of plastic debris which undoubtedly came from one of 
the chain guides.  Now we have two things going on here:  a massive pressure 
leak out of the tensioner leaving nothing left for the bearings, AND a highly 
restrictive oil pump pickup screen.
This will cause bearings to fail just like this engine has suffered from.  
Depending on how the debris settled out of the pickup screen and got sucked 
back in, it would have blocked anywhere from at least 50% of the oil pickup to 
90% of it.
 
Now, hopefully it didn't jump time and bend valves and stuff.  Other than the 
lower end noise it ran very good and seemed to make all of its power.  I didn't 
beat on it because I was worried about sending a rod out the side.  Bye bye 
$350 core.
 
I've been reading some internet forums on what causes these things to sludge 
up.  I guess a big concern is the oil return passages being too small or 
something.  I strongly disagree.  They are big and there are plenty of them.  
That is not the cause.


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