CAM BEARINGS & CRANKCASE SEALING

TO ALL (!! -- A 'Must Read' for all Engine Builders)

It is NOT 'string' it is SILK. More specifically, it is #50 THREAD,
although I have seen a German-born, factory-trained mechanic spinning
free a few STRANDS from silk embroidery thread. This method applies
ONLY to the crankcase's EXTERIOR parting flange. NOTHING is applied
to the TOWERS around the cam-shaft. The interior parting line
associated with the CRANKSHAFT are provided with molded rubber O-
RINGS, except for the 8mm diameter studs associated with the #4
bearing. This IS NOT a main bearing as such. It was added to
compensate for excessive wear of the CRANKCASE. This will cause many
to frown but the fact is, the Volkswagen engine did NOT HAVE
replaceable bearing shells until the late 1940's, the crankshaft AND
the camshaft used the CRANKCASE as their bearings. Indeed, the
camshaft was not fitted with replaceable bearing shells until the
mid-1950's.

We owe the appellation of 'main bearing' to the #4 bearing to the
ignorance of American technical editors who applied that name, largely
because the #4 bearing was packaged with the three Main Bearings.
Prior to that time the pulley-end of the crankshaft continued to use
the parent metal of the crankcase as the bearing for the crankshaft.
Alas, the eccentric pull of the dynamo/blower resulted in eccentric
wear of those 'bearings.' This wear was exaggerated after the three
main bearings were fitted with replaceable steel-backed bearing SHELLS
in the mid-1950's until a replaceable bearing was provided for #4 as
well. This transformation took more than a year and resulted in many
an arguement among VW mechanics... which continues to this day, in
that some insist on calling the #4 a 'main' bearing despite the fact
this particular race was NOT initially fitted with a replaceable
bearing shell until some months after the three main bearings were
fitted with replaceable bearing shells. The arguements continued even
after the issueance of a Servvice Bulletin giving specific dimensions
for opening up the early-model crankcases to accept a replaceable ring-
type bearing shell.

In the same vein, the cam was NOT provided with replaceable bearing
shells until the 1960's. This was taken as 'proof' that the
replaceable ring-type bearing shell was in fact a 'main' bearing.

The truth is, it doesn't really matter, does it? In overhauling the
lower end, if you happen upon an engine that still has the cam running
in the parent metal of the crankcase, the engine is more than fifty
years old (!) and should be returned to RIMCO to have the crankcase
overhauled so as to accept replaceable shells for the camshaft. Or
to have the thing mounted on a pedistal as an example of German
engineering, in that the engine has survived more than half a century
of use.

-Bob Hoover