Worn PW3 cam

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

  1. comnoz

    comnoz VIP MEMBER

    Joined:
    Dec 10, 2008
    I can't say where the failure started on the failed PW3 cams I have. They were too far gone to tell.
    I have however seen the beginning of failure on several standard and combat cams where tired valve springs were likely the reason for failure that started on the closing ramp just after peak lift.
    Here is a trace of a cam that was used with exhaust valve springs that had deteriorated to ~50 lbs of seat pressure. You can see the point of maximum wear is just after peak opening of the exhaust valve. The purple line is the worn cam. The blue line is a new cam.

    damaged cam verses new.png
     
  2. oldmikew

    oldmikew

    Joined:
    Jul 25, 2015
     
  3. Madnorton

    Madnorton

    Joined:
    Jun 9, 2008
    There are some owners worldwide that cover more than 40K a year, there are some Commando's out there that have done over 200K miles with the same owner from new. Ken's mileage is not unusual, many do that even in the UK.
    The rules with cams are simple in theory, think what an ideal timing system would be and and then work out what you have to have inreality, then you can see the compromises involved, that is when you realise it is a lot more complicated.
    Three things kill cams, debris, incorrect set up and lack of / incorrect lubrication, irrespective of what type of material it is made of, pick one of three and the cam is on a hiding.
    I'm sure when Ken has his cam tested, the truth will come out.
     
  4. Fullauto

    Fullauto VIP MEMBER

    Joined:
    Apr 13, 2009
    I think you are in dreamland. 40,000 miles a year? That would mean you would be on the bike full time, year round. Many do my mileage? Ha! Where are they? You never hear from these people. Never.
     
  5. Snotzo

    Snotzo

    Joined:
    Mar 12, 2013
    Fullauto
    it would be of interest to learn what the preparation was that was applied to your followers, also how many lobes suffered wear on your PW3.
    If the preparation was of the DLC type, the surface to which it is applied is impregnated with an extremely low friction matrix of diamond like carbon particles, usually leaving the surface colored black or a very dark blue, and would possibly be the reason your followers have survived while the cam has not - this despite what must have been a very abrasive contact between the worn cam lobe and it's follower.
     
  6. SteveA

    SteveA VIP MEMBER

    Joined:
    Dec 20, 2011
    I am inclined to think it does mean something, it means the cam is from an earlier batch. I like the performance of a PW3, but having one fail did not incline me to fit another. Particular with the prospect of being revved to 8K.

    My cam showed a couple of faults during installation, like inacccurate lobe centres to 'discussed' data, and a poor thread for the cam nut. Very little data on the cam is actually provided with it. But I carried on. It completed 26 races in one season, I loved its characteristics, very easy motor to use, but the cam failed at some point during the last few races.

    I checked and measured everything mentioned by ZFD and am happy that installation was not the issue. No coil binding, no excess spring pressure and adequate piston to valve clearance. Lubrication, well maybe, can't be 100% conclusive on that.
     
  7. worntorn

    worntorn

    Joined:
    Dec 22, 2006
    I simply meant "in use for years" is not a measure of wear life.
    Its like measuring fuel mileage by saying a tank of fuel lasted all summer.
    In fact, for a lot of these bikes a tank of fuel does last all summer!
    We did a mileage poll here and most did not break 5000 miles per year or even close.

    Also, 26000 miles isnt so bad for a high lift set up. We have to accept that increased lift brings increased wear. For most it doesn't matter.
    26,000 miles divided by 1500 miles per year= 17 years riding
    63+17 =80
    Yikes!




    Glen
     
    Last edited: Apr 25, 2018
  8. olympus

    olympus

    Joined:
    Aug 5, 2017
    I was about to purchase a PW3 cam.... now I'm not so sure
    As long as all the precautionary measures are taken, clearances along the full drive train & regular oil drops on a machine doing 3/ 4000miles tops a year.... am I worrying over nothing??
    Has there been any response from the suppliers on these premature failures
     
  9. Staytite

    Staytite

    Joined:
    Oct 15, 2011
    Hi

    Many years ago Norman White built an 850 bottom end with a PW3 for me. In the build sheet it states in Norman's hand writing
    "assembled with 'Graphogon' colloidal graphite grease"

    It states at the top of the PW3 Camshaft Data Sheet supplied by Norman;

    "Important

    On assembly use a colloidal graphite paste on followers and cam lobes. Use new or reground followers only."

    I also seem to remember reading that damage to PW3 cams could be caused by an engine with a PW3 being turned over by hand
    without the correct graphite colloidal grease while the engine was being assembled . This caused spalling to occur that was
    subsequently exacerbated when the engine was started. Hence the use and warning on colloidal graphite grease

    What do you guys think?
     
    Last edited: Apr 25, 2018
  10. olympus

    olympus

    Joined:
    Aug 5, 2017
    I have used Graphogen for more year than I care to remember.... the write ups on this product speak for themselves
    It is well worth the money, and it will be liberally applied to all engine internals when I rebuild
     
  11. Robert_Norton

    Robert_Norton

    Joined:
    Dec 21, 2008
    .



    Mr. Comstock's spintron video on youtube for the PW3 cam:










    Mr. Comstock's youtube video channel, with spintron analysis of many more cams:


    https://www.youtube.com/channel/UCSn9JCMr-y7D1vVJFT4IJ8g/videos




    Spintron accessnorton.com thread, which is required reading in order to be as knowledgeable as possible about Norton camshafts:

    https://www.accessnorton.com/NortonCommando/about-time-for-the-spintron.18787/





    Looked for a spintron video of a stock Norton cam for comparison on bounce characteristics, but was unable to find one. Read the whole Comnoz spintron thread in the past and seem to recall the information might be in there somewhere. If not, would like to know if/when/where valve bouncing typically occurs with stock Norton cam.




    Only Norton I've ever had that would take it to 7K in fourth gear, was a '74 850 Roadster, stock bottom end and pistons, RH10 head (milled .010 for compression increase), dual resleeved Amals, factory ham-can air filter, Boyer ignition, gutted Dunstall Decibel mufflers, no-crossover headers, no fairing, and it had a 20 tooth countershaft sprocket. Read 110MPH on the speedo.





    Didn't know about faulty gearbox bearings back then ...






    .
     
  12. jseng1

    jseng1

    Joined:
    Nov 26, 2009
    When a cam wears out the nose gets worn down.


    The original cast iron cam failed on the nose on both lobes in the photo below.

    [​IMG]


    Even hard welded cams can fail at the nose (see photo).

    [​IMG]

    Full Auto doesn’t want to have another failure. A hard welded cam should do the trick. But it couldn’t hurt to use springs with closer to stock pressures such as the Kibblewhite OEM springs instead of high pressure conical springs. Full Auto’s bike is not a high RPM bike – it has a single carb and he enjoys low and mid range grunt - it has no problem with loss of valve control and he doesn’t need elevated spring pressures.

    Robert_Norton
    You can see obvious valve bounce in the spintron tests AFTER the valve has returned to its seat and that means that the lifter is on the ramp or the heel of the cam - rarely do you see cam damage there.
     
    Last edited: Apr 25, 2018
  13. worntorn

    worntorn

    Joined:
    Dec 22, 2006
    Best Mid range grunt = RV cam not high lift race cam.
    But I suspect he will get an RV cam of sorts, it'll be the right cam for the job, I'm sure.
    We could still call it a PW3!

    Hi lift when you don't need it reminds me of the kid who mounted a giant 4 bbl Rochester on a 283 chevvie, back in highschool.
    The 2 bbl cars were way faster but didn't have the bragging rights when the hood was lifted. Or removed totally with just the hinges pointing skyward, which was the favourite when running a huge 4bbl.

    Glen
     
  14. Fullauto

    Fullauto VIP MEMBER

    Joined:
    Apr 13, 2009
    Ok. It's early in the morning. What's an "RV" cam?
     
  15. bill

    bill

    Joined:
    Jun 1, 2003
    an RV cam is for low end torque. used in towing trucks and motor homes with gas engines.

     
  16. ntst8

    ntst8 VIP MEMBER

    Joined:
    Feb 14, 2004
    The following is a cut and paste from the NOC forum, Posted by Charles Bovington at September 09. 2013and recently resurrected.

    Cast iron is a suitable material for low cost mass production of camshafts for low stressed camshafts. The chilling gives a hard white iron layer on the surface which is relatively wear resistant.

    For small volume production and for high performance engines camshafts manufactured from steel billet are preferable. Accurate manufacture by CNC grinding machines allows for the production of a superior product, albeit at a higher cost.

    In both cases cast iron and steel, careful control of chilling or heat treatment is essential as is the difference in hardness between cam and follower.

    The cam/follower interface is the most highly stressed part of the engine. With chilled cast iron, the tensile stresses caused by the cyclic loading experienced at the interface and/or by lack of rigidity in the camshaft can cause sub-surface cracking which, when a grain boundary in the structure, cause lumps to fall out (pitting). Heat treated steel does not suffer this problem because of its higher tensile strength.

    There are many pitfalls waiting for the maker of steel cams, the induction hardening process for steel camshafts must be carefully controlled, I know of at least one manufacture who found that he was getting lots of warranty claims on new cars soon after delivery.

    We found that the cam hardness varied greatly along the cam shaft and showed them that this was a result of the induction hardening and quenching process. We also supplied a special cam lubricant to help them while they got their heat treatment right.

    Flatness of the cam in the transverse direction is also a cause of problems. I chaired the working group which developed the valve train scuffing test which is used in the ACEA engine oil approval system. This uses a Peugeot engine and we found that, using the 'good' reference oil, we could get failing results for cam wear and scuffing on some cam lobes and followers and good passing results on others. Careful measurements showed that inaccuracies in grinding lead to slopes across some lobes such that the oil was squeezed out of the side of the contact causing starved lubrication and scuffing. Peugeot installed a state of the art cam grinder and produced 1000 perfect cams. The problem went away.
     
  17. comnoz

    comnoz VIP MEMBER

    Joined:
    Dec 10, 2008
    The cam I am doing for Ken is a copy of a PW3 that has been modified for less jerk and has a slightly rounded nose so it does not tend to loft the valve as easily as a PW3 does. It is still what I would consider a full race cam. I guess you can call it a JC3....:rolleyes:
     
    Fullauto likes this.
  18. worntorn

    worntorn

    Joined:
    Dec 22, 2006
    I thought you were reducing lift?

    Glen
     
  19. comnoz

    comnoz VIP MEMBER

    Joined:
    Dec 10, 2008
    I have definitely spun up a stock cam. They do not have bounce problems -if the stock springs are fairly fresh.
     
  20. comnoz

    comnoz VIP MEMBER

    Joined:
    Dec 10, 2008
    The lift is reduced as a product of rounding the nose -but not by very much. And the duration is less at .050 due to the smoothed ramps -but again - not by much.
    Seat to seat stays the same and duration at higher lift stays within a couple degrees.

    Ken likes his PW3 cam and has had good results powerwise -so that is what I am staying with.
     
    Nater_Potater and Dano like this.

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