HELP! I-5 crankshaft end-play problem
armanmik at earthlink.net
Thu Feb 5 09:18:55 EST 2004
> Even though the silvery surface was removed and copper showing underneath,
>This is _wrong_ - the silvery surface is the bearing material and the
copper underneath is the backing.
Ameer, this is STILL wrong.
According to Federal Mogul's book "Engine Bearing Service Manual" - and I'm
willing to bet that Federal Mogul knows a LOT more about bearings than your
race guy, on page 114 they have a fabulous picture of a set of bearings
assembled with insufficient clearance - and it is not pretty.
Page 36, EXACT QUOTE: "In the manufacture of gas, gasoline and diesel
engines today, precision bearings are in almost universal use. Such
bearings are manufactured to such exactness that no boring, scraping or
other fitting is necessary at assembly. In fact, any tampering with this
type of bearing usually results in a poorer fit, sometimes leading to early
Further - the "shiny" stuff is babbitt metal - THAT is the bearing
material, NOT the copper, which is plated onto a steel backing which
supports the whole shebang.
The babbitt metal not only provides the bearing surface, but it "catches"
bits of abrasive material (grit, sand, metal), and "heals" over it, keeping
the crankshaft from being scored. In severe cases, the grit is too big to
embed into the babbitt, and the crank will be ruined anyway. If you have
removed the babbitt, anything that gets in there will be held by the
copper, just like a cutting tool in a lathe, and it will ruin the crank in
There are several bearing technologies which use different combinations of
different metals, but if the bearing is sized correctly, you will NOT need
to sand anything to fit - someone has given you the wrong parts, or the
crank was cut incorrectly or SOMETHING - but this is NOT right!!!!
If you want this engine to live, find out why it didn't fit together
properly the first time. And engine that won't turn, won't run. Besides, if
the extra coating wasn't needed, why does the Audi accounting department
let them get away with it? It costs money to apply, and more money later to
remove. And it slows down production if each thrust bearing has to be
The thrust bearing takes the entire load of the clutch springs (when you
depress the clutch, think where the effort goes!), and it locates the
crankshaft fore and aft in the block. If the bearing fails, the entire
engine will become scrap pretty quickly.
Ameer, do not run this engine until you figure out what is wrong. If the
machinist still insists he's right, get a second, professional opinion.
Kneale got it right, too - race engines are torn down every 500 miles,
while we fully expect an I-5 to go 250,000 (or more) miles between
overhauls - that's 500 times as long.
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