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Date:         Fri, 7 Nov 2003 09:52:25 -0700
Reply-To:     Dyer Lytle <dyer@LPL.ARIZONA.EDU>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Dyer Lytle <dyer@LPL.ARIZONA.EDU>
Organization: U of A LPL
Subject:      An Amateur's Rap on Camshafts
Content-Type: text/plain; charset=us-ascii; format=flowed

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


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