Date: Wed, 23 Oct 2002 21:36:51 -0500
Reply-To: Stan Wilder <wilden1@JUNO.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Stan Wilder <wilden1@JUNO.COM>
Subject: Engine Balancing
Content-Type: text/plain; charset=us-ascii
Over the years I've acquired and rebuilt about ten Air Cooled Type IV
engines.
It has always been my standard procedure to disassemble engines and
maintain all of the parts together.
The purpose in this is to have all of the parts and investigate why the
engine failed.
Some things just jump out at you like dropped valve seats, crank bearings
that missed the pins, cylinder head gaskets cut by leaks, burned out rod
bearings.
Many of these things lead you to believe that the single thing caused
failure.
I've seen engines with a dropped valve seat and a valve stem just hanging
on by a thread on an opposing head.
If you can evaluate the mileage on the engines by crankcase stains,
cylinder head stains, carbon deposits on pistons and valves and rod
bearing wear, cam shaft wear, roundness of the rod big ends / crank shaft
bearing bores and you can find the cause of failure is related to several
things.
Each engine is a special case and we all know something has to fail
first.
In many cases the first failure crippled the vehicle but had this part
not failed there was another in line to kill the engine.
Part of my evaluation is to weigh each piston assembly and rod to see how
close they are in weight.
My first adventure with this was at Allied Fastener that weighed some
parts on their very precise fastener counting scale.
I doubted the results because the pistons and rods were very close in
weight, never more than one gram difference.
I considered that the law of averages was fighting me but after buying my
own electronic scale, I've weighed OEM, Cofap, Mahle and Japanese pistons
and never had anything more than one gram out. (scale has +1/-1
accuracy.)
With rods I seldom find them more than two grams out even after 20 years
of use and several reconditioning. The proper way to weigh rods is
......... weigh each end. Even with this more critical weighing process
the rods were still within one gram on each end. (Weighing both ends not
much of a trick, fixed rod from scale center mark, weigh one end, turn
the rod around and weigh the other end.)
Example: Rod nut 6 grams.
It shows why the big end of rods balances: IE 1gr is a lot of steel and
reconditioning rods seldom removes much steel.
Now that I've got you yawning .................. engine balance in VW
engines is very good, I've never found a VW engine that was far enough
out of balance to cause engine failure.
I'm hoping that this has answered the age old question "Why do Waser
Boxers Throw Rods?".
If they are as precise as Air Cooled : It ain't the balance.
Stan Wilder
________________________________________________________________
Sign Up for Juno Platinum Internet Access Today
Only $9.95 per month!
Visit www.juno.com
| 
