Hi all,

A few days ago I posted a message to this list asking about
camshafts and the very different prices that I found for them from
various vendors.

Since then I have had a very nice conversation with Bob Donalds at
Boston Engine and I have done some research on the web about
camshafts, regrinding, surface hardening, and etc.  This message
is to document some of the information I have found to the
vanagon list.

My confusion began when when two people with much more experience
with VW engines and machining techniques then I offered me two opposing
opinions about the way to go when looking for a replacement camshaft
for the 1.9L VW water-cooled boxer engine that I am in the process
of rebuilding.

A camshaft must have a few of characteristics in order to function
properly and to have an acceptably long service life.

  1. proper dimensions of bearing races, cam lobes, and gear drive.
  2. polished bearing and cam surfaces.
  3. sufficient surface hardness to combat frictional forces in the engine.

In general, camshafts, OEM, and aftermarket, are induction hardened (if
they are hardened at all, see below).  My research tells me that induction
hardening is a surface hardening technique.

To quote from the DOE's Office of Transportation Technology's paper
"Intelligent Induction-Hardening":

"Induction hardening is an energy-efficient, in-line, heat-treating
  process widely used in the automotive industry to surface-harden these
  kinds of parts at the lowest possible cost. The substitution of induction
  heating/hardening for furnace heating/hardening can lead to savings of
  up to 95% of the energy used in heat-treating operations, in addition to
  the energy savings enabled by optimization and lightweighting of automotive
  powertrain components.

  Induction hardening is accomplished by passing an alternating current
  through a water-cooled copper coil that is coupled to the part by the induced
  magnetic field. The alternating magnetic field induces eddy currents that
  resistively heat the outer surface of the part. The part is then quenched
  to martensite, a strong, wear-resistant phase, when the austenitized layer
  becomes sufficiently thick."

If you go to the "J.J. Castings" web site and read the section on induction
hardening:

      http://www.jjcastings.com/induction.htm

they say that it is possible to use induction hardening to harden a
surface to a depth of from .5mm (.020") to 20mm.

So, if regrinding a camshaft, the wear+regrinding must not penetrate
this surface hardening or else the camshaft must be rehardened.

Also, with reground camshafts, there can be problem with the size of the
bearing journals.  To quote from the Engine Rebuilders Association newsletter:

    http://www.aera.org/Members/EngineTech/edge1196/page2.htm

"There isn't much that can be done with the bearing journals of a used cam.
  After the lobes of a used cam are re-ground, the journals are polished to a
  slightly undersized condition. Unfortunately these undersized cam journals
  can lead to excessive oil clearance. This additional oil clearance can result
  in lower overall engine oil pressure. If a "new"" cam is used, you can be
  assured that the journals are of the proper size and no oil pressure will be
  sacrificed."

This same article mentions that (some) new cams are flame hardened, which is a much
deeper kind of hardening than induction hardening:

"Long term resistance to wear is aided by heat treating the surfaces of a cam.
  Most OE cams have a thin layer of induction hardening. These hardened layers
  of a "used" OE cam may be worn thin during it's first life. When a used cam
  is re-ground, much (or all) of the hardened surface can be removed resulting
  in a less than ideal situation.

  A good quality "new" cam is usually flame hardened resulting in a deep
  hardening that will easily last the life of the engine."

I have been told that some of the cheap aftermarket camshafts available
are not hardened.  They depend on "work hardening" to harden their
surfaces during engine operation.  The problem with this is that the
metal must deform in order for work hardening to take place.  This means
that, to some extent, the shape of the camshaft lobe must CHANGE before
the hardening takes place.  To me, this is not a good thing.

Now as far as vender's cams go:

Volks Cafe says on their website that their $65 camshaft is NEW.  I called
them and they told me on the phone that the camshaft is a REGROUND camshaft
and that it only comes in one size gear (0).

Bus Depot, whose cam is $138 assures me via e-mail that their cam is brand new,
US made, and hardened.  I haven't asked about the sizing yet but because
of the bearing journal wear problem I am considering a new cam.

I have not contacted Van Again about their $259 camshaft.

I have written an email to the people at Elgin cams, asking various questions.
They were recommended to me but I have not heard back from them yet.

There is a discussion about cams going "flat" in VW engines on the web at:

  http://www.oceanstreetvideo.com/vwtech/CamsGoingFlat.htm

More later when I have further information...

  -Dyer Lytle in Tucson