Worn PW3 cam

Discussion in 'Norton Commando Classic Motorcycles' started by Fullauto, Apr 20, 2018.

  1. comnoz

    comnoz VIP MEMBER

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    Dec 10, 2008
    As far as I know Norton used a Stellite foot on the followers in all the twins.
    The grade of Stellite on the cams is not as hard as the lifter.
    Comnoz
     
  2. nortonspeed

    nortonspeed

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    Jun 29, 2008
    FYI the very early 500 twins used fully cast iron followers (without Stellite foot) with 3" radius foot.
     
  3. comnoz

    comnoz VIP MEMBER

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    Dec 10, 2008
    Thanks, that is good info.

    I recently did a top end for an iron head 500 twin. It had 3" radiused lifters with a brazed foot. I have no idea if they were original.
     
  4. nortonspeed

    nortonspeed

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    Jun 29, 2008
    Those 3" radiused lifters could very well be original because the first lifters were just plain cast iron with 3" radius foot then cast iron with 3" radiused brazed stellite foot were used (both for a short period of time) and then the cast iron lifters with flat stellite foot as we all know them. Note the original 3" stellite foot were a lot thicker at the lobe centre. I preferred those for racing as grinding a 3" radius in the later flat stellite foot would make the edges of the stellite foot rather thin.
     
    Last edited: May 17, 2018
  5. oldmikew

    oldmikew

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    Jul 25, 2015
    Wonder if anyone can still supply the 3" radius tappets? Your point about the edges is noted
     
  6. comnoz

    comnoz VIP MEMBER

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    Dec 10, 2008
    No new 3 inch folowers that I know of.

    But 3 inches will work on a Commando tappet -if the cam is not too racey.

    Or there are cams that will work in the 500/600 with flat Commando followers. Comnoz
     
  7. oldmikew

    oldmikew

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    Jul 25, 2015
    Something still sticks in my mind about the spec for the 72 engines and stellite . Perhaps the factory increased the thickness , but if its ground off then it will be thinner at the edges and liable to crack. Puts me off having radiused followers which in turn rules out some interesting US cams .
     
    Last edited: May 18, 2018
  8. comnoz

    comnoz VIP MEMBER

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    Dec 10, 2008
    The earlier lifters [-pre 72?] had the front and rear of the Stellite beveled off. These lifters can accept a 3 inch radius and I have never seen one of them break the Stellite.
    But I have seen a few of them loose the Stellite -radiused or not..

    The new spigotted lifters also have a thicker foot. I have ground a 3 inch radius on these also and have not seen a problem. I would not use less then 3 inches on either of them.
     
  9. oldmikew

    oldmikew

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    Jul 25, 2015
    Thanks very much for sharing and noted.
     
  10. SteveA

    SteveA VIP MEMBER

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    Dec 20, 2011
    Indeed, I have Comnoz radiused AN new stock followers running with my Comnoz supplied Webcam.
     
  11. oldmikew

    oldmikew

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    Jul 25, 2015
    Could well be the way to go. What concerns me about the PW3 issue are the people its happened to.
    Clearly you and Full Auto both know how to build and treat an engine. It has made me have a long hard think about cams.. Apart from my road bike which I might recam when I split the cases , am also building a Maney based 750 for my nephew to hill climb
     
  12. SteveA

    SteveA VIP MEMBER

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    Dec 20, 2011
    I wish I had that level of faith in myself...but I don't normally have too many bits left over :(.

    I think there is an issue of PW3 suitability above 7K, which many will consider abuse anyway. To ride on a race circuit, it is a great cam. But a race bike needs rpm available above peak power, a road bike doesn't.

    I have a really good original standard cam that I would use if I built a road bike!

    For the hill climber in youthful hands, unless you are going to constrain him with a rev limiter, look west. :cool:
     
  13. Fullauto

    Fullauto VIP MEMBER

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    Apr 13, 2009
    Interesting fact via the metallurgist. The two failed PW3 cams which are, of course, chilled iron, as tested were as hard as a steel or hard welded cam.
     
  14. Fast Eddie

    Fast Eddie VIP MEMBER

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    Oct 4, 2013
    That is interesting!

    What the hell is going on then?
     
  15. ando

    ando

    Joined:
    May 25, 2011
    Fullauto, is the wear on your cam lobes even or just one lobe that has suffered.

    It was mentioned to me that the photos shown on page 8 of this thread appeared to show differing amounts of wear on the lobes of the same cam, with the cam described as a soft 850 cam clearly evidence of wear on one lobe only. If it is just one lobe that has worn then the question to be asked would be why just the one lobe. hopefully someone has an answer.

    ando
     
  16. comnoz

    comnoz VIP MEMBER

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    Dec 10, 2008
    A cams resistance to wear is not only determined by it's hardness.
    I have seen many very soft MK3 cams reach 100,000 miles.
    Chilled iron is hard and brittle. But I would not use a cam made from it on a Norton.
     
  17. comnoz

    comnoz VIP MEMBER

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    Dec 10, 2008
    Likely just that lobe scuffed first. From there wear progresses quickly.

    Maybe because that spring went soft first or the valve adjustment was different or the main oil supply which is the oil thrown from the rod journals was a little less on that journal or who knows.

    PS, It is pretty much impossible to have one soft lobe on a case hardened cam.
     
    Last edited: May 24, 2018 at 10:42 AM
  18. nortonspeed

    nortonspeed

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    Jun 29, 2008
    This is what Andover Norton say about their camshafts:
    Andover Norton camshafts, and around 90 % of all production car camshafts, are made from “Chilled Iron”. Chilled Iron is around 25% better than normal case hardening steel and around 15% better than nitrided steel at resisting wear. This materials ‘wear scuffing factors’ give the camshafts longevity and improved wear characteristics over even original Norton production camshafts. It works better than other materials due to a matrix of carbides being formed when cast. The cam lobe shape is formed by the metal chill casting process; when the molten metal comes into contact with the cam lobe areas of the casting it changes the structure of the iron to form a matrix of carbide approximately 4 mm deep. It all comes down to “Tribology”, which is the interaction of surfaces rubbing together and the scuff resistance of the materials that are rubbing together. When Jaguar were sports car racing they had repeated failures using nitrided tool steel camshafts. They began using chilled iron camshafts and never had another failure

    Jim, please explain why you do advise against chilled iron camshaft for a Norton?
     
  19. comnoz

    comnoz VIP MEMBER

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    Dec 10, 2008
    1. Weak threads makes it difficult to keep the drive sprocket from damaging the keyway. The need to coat the area in red locktite to keep it from moving is not my idea of a good design.

    2. I have seen a couple chilled iron cams broken in half. [trashing the engine when it happened] I have never seen that with a steel cam. No doubt influenced by the long cam with no center support.

    3. I am aware that the chilled iron lobe is supposed to be a very good wear surface. But my experience with using the available chilled iron cams on a Norton has not been very good. I can not say if it is a compatibility problem with the grade of Stellite or if it it due to deficiencies in the manufacture or maybe borderline lubrication.
    It may also be due to the high jerk of the PW3 cam.

    I will simply stay with and recommend what has worked best for me in the past. Comnoz
     
    Last edited: May 24, 2018 at 4:31 PM
  20. jseng1

    jseng1

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    Nov 26, 2009
    One bad lobe is more common than you think - this has been happening on a lot of 850s with stock cams. The other lobes may be perfect.
     

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