HELP! I-5 crankshaft end-play problem

[Mike Arman]

>  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 
failure."

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 
short order.

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 
hand-fitted.

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.


Best Regards,
Mike Arman