Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: Notesfiles $Revision: 1.7.0.8 $; site convex
Path: utzoo!watmath!clyde!burl!ulysses!mhuxr!mhuxn!ihnp4!inuxc!pur-ee!uiucdcs!convex!tmorris
From: tmorris@convex.UUCP
Newsgroups: net.auto
Subject: Re: tech. ques.
Message-ID: <82600013@convex>
Date: Sat, 21-Sep-85 10:36:00 EDT
Article-I.D.: convex.82600013
Posted: Sat Sep 21 10:36:00 1985
Date-Received: Sun, 22-Sep-85 23:45:44 EDT
References: <202@kitc.UUCP>
Lines: 26
Nf-ID: #R:kitc.UUCP:-20200:convex:82600013:000:1726
Nf-From: convex.UUCP!tmorris    Sep 21 09:36:00 1985


	In most modern engines , bearing inserts are used . These alloy
surfaces , often called shells, are made in two half-circles . When they
are assembled in a rod or main bearing , they are the nearest metal surface 
to the crankshaft , forming the circular bearing surrounding the smooth
wearing surfaces. In theory ,and if all goes well ,they never touch the 
crankshaft .They ride upon a steady film of oil being pumped through
hollow passages in the crankshaft by the oil pump.
	And therein ,literally , lies the rub . If the flow of oil should
be insufficient , even for a short time , the bearing surface touches the
crankshaft . At this point , wear begins in earnest . When the friction 
caused by this wear creates enough torque to overcome the small keys that
hold the shell in place , it rotates with the crankshaft . This can cause 
immense damage to the surface upon which the shell was mounted . 
	If it is a rod bearing , it may generate enough torque to snap off 
the rod and beat it about the crankcase. You will definitely be aware there
is something wrong at that point. Sometimes a tapping noise will preceed
this catastrophe. If you suspect it , it will be worth your while to have it
checked out with a stethoscope. Its the difference between a rebuildable engine
and a high-tech boat anchor.
	If it is a main bearing , when the shell spins it will obstruct the
hole in the block from which life-giving oil is pumped into the bearing and
crankshaft. I have seen several blocks ruined like this , as the mounting 
surface for the bearing shell is destroyed beyond repair . Broken crank-
shafts can also result . Sometimes a deep knocking sound will preceed failure ,
other times it all just comes undone.


Brought to you by Super Global Mega Corp .com