<VV> Re: Rod bearing wear

[N. Joseph Potts]

I think it's worth noting from the original report that THIS bearing (alone)
was subject to some very unusual, and possibly severe, hammering from the
triggering event, the throwing of the valve seat. When the seat is cocked in
the head, the valve cannot descend enough into it, and so the top of the
piston hammers on the valve, sometimes breaking the valve seat. I would
expect this to affect the rod bearing pretty quick. Maybe the crankshaft
journal, too.
     I've been driving for over a year now with two cylinders so affected.
The pistons are "dimpled." I left them that way after replacing the head. No
doubt, the bearings (at least those two) on my crankshaft are down to the
copper, too. Anyone interested in buying my car (my price is outrageous) ?

Joe Potts
Miami, Florida USA
1966 Corsa coupe 140hp 4-speed with A/C

-----Original Message-----
From: virtualvairs-bounces at corvair.org
[mailto:virtualvairs-bounces at corvair.org]On Behalf Of djtcz at comcast.net
Sent: Sunday, June 12, 2005 2:37 PM
To: virtualvairs at corvair.org
Subject: <VV> Re: Rod bearing wear


I would not spend 10 seconds worrying about bearing materials, oils,
additives, or "lugging" the engine with tall gearing.

 Down to/through the copper in 27,000 miles is quick, but I'd have expected
a gross journal roundness or size error to make itself known much quicker
(maybe within minutes after starting, or during the first high speed run).
I'd actually expect that much bearing wear to start the warm oil pressure to
dropping.

Was the crank ground and re-tufftrided? Regardless, Who polished it?
A local heat treater warned me a long time ago to be sure and polish a
tuff-trided crank in the operating direction.  Since then the recommendation
has appeared more and more.

Any measuring or plasti-gaging done?

Had you loaned the car to someone recently, or had the oil changed by
someone?

Not knowing the pressure history makes any guess just a guess.

bearing failure troubleshooting guide here.
http://www.engineparts.com/motorhead/techstuff/bearingfailures.htm

Note the difference in smoothness and length of the worn surface between
"normal" and accelerated.

Lets Assume for a moment, and strictly for the sake of argument, lubrication
was adequate (since without a pressure history the lubrication situation is
unknown, and a mystery).  Under "accelerated wear" they focus on journal
surface finish a lot, and say this - "Wear in the presence of adequate
lubrication to prevent heat build-up and wiping is caused by peaks in the
journal surface finish profile which penetrate the oil film and abrade the
bearing. Always grind opposite to rotation and polish in the direction of
rotation. "