The 30,000 mile replacement recommendation for bearings comes from various
recommendations I've seen and heard over the years for the 1500. The 1500 is
darn hard on its bearings, and has a noted record of wiping them out, and then
wiping out the crank and other rotating/reciprocating pieces. The harder you
drive it, the harder it is on those parts. The replacement recommendation is
simply a preventative maintenance aproach.
I tossed the thrust washers into the equation on the basis of you being down
there already, and as such I'd replace all the bearings, not simply the rod
bearings. It's just as easy to replace the thrust washers, if they aren't
pinned.
The regular oil changes with good oil will indeed go a long way in protecting
the bearings, but they are still going to get pounded. Especially if you rev
the 1500 up. It's just an acknowledgement of the inherent characteristics
(flaws if you will) of the 1500.
I don't feel comfortable offering feedback on your 1/32 inch supply hole size
on the thrust washer. I don't know the flow rates of the oil pump, don't know
the leak rate at the various other bearings, and as such, I truly cannot say if
1/32 is ok or not. I simply don't know the answer factually. Weigh any and
all replies you get to this hole size carefully. After all, if it's too large,
you'll wipe out your engine. I would say a pressure gauge should be a must
just for monitoring purposes.
Drilling the matching hole larger in the thrust washer itself will help, but
that still will not ensure the thrust washer doesn't lift off the block and
start riding against the crankshaft. As long as the thrust washer is free to
move, oil will flow under it. How significant this will be I hesitate to
speculate. But I can say I've always observed that things floating freely in a
pressurized stream always get pushed downstream as far as they can go.
The splash on the front thrust washer may be enough to protect it. I simply
don't know if it will or not. But oil pressure on the rear thrust washer will
push the crankshaft backwards. How hard it pushes it backwards will be a
function of the thrust washer clearances (the tighter they are, the harder it
will push backwards), oil pressure and oil viscosity. It would cause long term
wear on the front thrust washer, I just don't now if it will be significant or
not.
My suspicion is that this thrust washer modification is superfluous, in a
similar manner to the rocker shaft external oil line modification. But in any
case, I'll follow the story with interest.
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