Worn PW3 cam

Status
Not open for further replies.
Is this newsletter avail to the public?

The AN news letter is a simple sign up to receive it, might be every other month or so publication and guess there would be a link to do so on the website.

It is an interesting read, new parts, customers bikes etc etc.
 
I also enjoy reading the AN Newsletter,but in its paragraph about the Camshaft failures it says the Australian camshafts failed due to "other factors",but does not state what that is.
Who is going to confess up?
Brett
 
Its all mentioned in the latest AN news letter. (email)
Although, the newsletter still leaves the question of what the issue with the cams actually was - the newsletter only says what it wasn't.

Quoting: "We have now put the camshafts on sale again, having understood the problems with the Australian camshafts were not caused by these but by other factors."

I seem to recall there was also a fault found with a cam AN had in their stock.
Transparency would demand that the fault(s) were made public together with the solution.

Rob
 
Unf
Having just read the newletter, may I post a quote that should be written on the soul of everyone with an old bike especially those of us of
a certain age:
<The way to build a Commando engine as I did in my university days, i.e. to take items out of the bag and put them together as per parts diagram is not good enough by far>

Joe, no truer words were ever spoken.

Unfortunately, not only is it 'not good enough', it is isn't actually possible!

One example is relevant here, the followers I received via Norman White from AN stock in 2014 had to be hand fettled to fit them in the bores in the original Norton barrels installed in my engine!

Joe gives a clue here by noting that suppliers don't like the time it takes to complete the job of grinding them to size!

Steve
 
Although, the newsletter still leaves the question of what the issue with the cams actually was - the newsletter only says what it wasn't.

Quoting: "We have now put the camshafts on sale again, having understood the problems with the Australian camshafts were not caused by these but by other factors."

I seem to recall there was also a fault found with a cam AN had in their stock.
Transparency would demand that the fault(s) were made public together with the solution.

Rob


The inference in Joe's omission combined with other statements is that the issue may be related to engine assembly procedures, and perhaps valve spring choices and valve spring set up.

In my own case I own my own spring pressure guage and a set of valve seat shims and use them, and always confirm that followers drop under their own weight when finally installed. I can also confirm that these issues get more attention than they did in the 1970s! (not least I didn't have a spring pressure guage then!)

Since my own PW3 failure occured after 26 races and several other track sessions, I would have thought such a basic issue as coil binding and excessive spring pressures would have shown up earlier. Also note that I have made no metalurigic investigations of the failure, and with Comnoz 'spintron' derived guidance I have simply adopted a cam and follower combination and setup I have reason to believe to be more suited to my above 7000rpm use.

I can understand that Joe and AN staff wish to be careful what they say with a significant, and potentially misinstalled, camshaft diaspora.

So, rather than speculate, which is what Joe has left us to do, I would rather that AN published engine build guidance in these areas, to include high lift installations, valve spring and pushrod choices etc. and made available to all, not just those who have made a recent camshaft and follower purchase.

What do you think Joe?
 
I'd love to see all these metallurgic reports that everyone has had done and what the outcome actually was.

The implication in the Andover newsletter is certainly that valve springs were at fault. Surely it is in their interest to definitively and publicly confirm this, as people building an engine will then buy cams, followers, springs etc... from Andover.

I have been collecting parts to build a top end as my budget allows, and would want to make sure that i buy parts that are compatible with each other. Ensuring compatibility may involve not using parts that i have already bought.

We are 18 pages into a very interesting topic here that many will refer to in the future, but i do feel there are lots of dark areas in terms of actual data.

Also Joe it is the Access Norton forum not nortonaccess
 
The surface fatigue on the cam lobe nose is a result of spring pressure - it can't be anything else. The problem is there is over 5 different manufacture types of springs being fitted, of which two have been tested. There is nothing anywhere to suggest that any real testing of actual spring rates, configuration, fitted heights, lobe nose pressures etc that enables anyone to say that 'this configuration will enable the cam to last x thousand miles' very few Norton owners record this data.
The feedback so far is that the for those that want high spring rates for performance cams then standard springs will easily fill this role but you need to check for coil binding. But many in the cam design and manufacture world are saying these pressures are way over the top, but can't suggest any figures that would be suitable.
This is further compounded by the fact that many may have felt what they believe to be valve lofting (bounce) at high rpm, has anyone actually physically seen this and recorded it with a camera. I suggest it could also be resonance which would give the same affect but is different in how it occurs.
Fitted height is important as it determines max lift pressure, so to keep the max pressure down you may need to go to a weaker spring rate, determine the max pressure you are aiming for, work out your valve lift, use the spring rate and work back to find your fitted height and at the same time making sure you do not get coil bound. We believe that those who have made changes to avoid coil binding have actually lowered their max pressures to a lower level.
I have just fitted and currently running a new cam, it has 11.24mm of valve lift and uses radiused followers with the cam ground to suit, predictions on paper using a standard head, with 1mm modified valve stems is that fitted pressure would have been 89 lbs, max 246 lbs, when fitted with the FA head I had fitted 59 lbs, a surprise, and max pressure 199 lbs as my fitted heights were different to a standard head, It is running nicely and will hopefully be dyno'd on the 31st. It will also be ridden to Austria if it survives the dyno.
The standard springs have not changed since 1961 when they were changed to to suit a performance cam at the time which went on to become the 06.1084. in that day and age, the idea was 'that should be about right' and a 'add a little more to be sure' were most probably the norm. Currently with a standard cam and springs you are looking at around 104 lbs fitted and 226 lbs max. If you only changed the cam to a higher lift version ie PW3 and did not change anything else you are now at 246 lbs max lift. This for an engine that max revs at 8K is considered way to much pressure these days, with some suggesting that this is where they would want to be with stock racer at 10,000rpm and above.
Some have also found that too much and lift and the thought process that more spring pressure to control the vale gear have found it costs rpm and saps power, some automotive cams have been modified to lower the lift and re-tested and the engine has been found to rev higher and not have a reduction in power, the customers requirements were still exceeded by using less lift.

Sadly we have established some knowledge, but still don't have any concrete answers or solutions.

Tappets - some like them to just drop in, OK with a new barrel, but what if they drop in a used barrel - how much clearance do you have? Some can wield a spanner and that's it, they do not know or can't be bothered to fit a crucial part like a tappet. Yes, it is time consuming, but not hard and it is worthwhile.
Being cast iron they are a pig to grind and the stress in the material will take charge when released from the mandrel and thus the little high spots. Of all the people in the Norton world, and many who worked for Norton in Wolverhampton and Andover in the past cannot remember how they were made then to avoid the high spots.

See you at the open day on the 28th at Andover Norton, come down and we can discuss further.
 
Interesting read, thank you.

I have fitted valve springs using measurements and pressures based on advice from the spring supplier and others with detailed valve train experience (who also use this forum). In effect I adopted a lower figure than that provided by the spring supplier.

You appear to be saying that installed spring pressure for a chilled cast cam is different to that used for a hard welded cam?

No max spring pressure figure was provided with the chilled cast PW3, data is limited to timing data. Though I note that it is indicated that the cam can sucessfully used with standard springs, actual pressure is not mentioned, but care with coil binding is. Nor am I sure that standard springs are suitable above 7000rpm (noting that my race motor is a 750 short stroke and with the PW3 fitted would rev to 8000).



'Tappet' is language many of the users on this forum don't regularly use, but of course it is the language used for ANs parts list. I think the UK norm is 'Follower' as in Cam follower, the US is generally 'Lifter', I use follower.

Your comment about desired fit and coping with worn barrels would be better supported by some detail on that at point of sale. I discovered the issue of fit at the point of fitting! Not ideal and frustrating.

Worn barrels are an issue, but AN sells new barrels, surely at the very least you should sell a set of followers that drop into those? Even if alongside followers designed to cope with worn barrels.

I believe that in the past followers were available in measured oversize to allow for worn follower bores. And where needed the holes can be honed to suit the oversize. Important since wear is unlikely to be totally even, and limited to the range of movement of the originally fitted parts, including cam lift. What that means is that if you are fitting a higher lift cam with used barrels, you probably need to hone anyway!

I have two used barrels and the followers did not fit either without rework. Once reworked, they fitted both at about the same clearance. We are not talking the odd high spot, each pair were measurably larger than the available holes.

Of course I may have found it more irritating than others did to have to do this since at the build time I was weekly commuting from Sussex to work in Italy and trying to build the motor at weekends, and with 4 grandchildren, to do some family stuff as well. It cost me 2 full weekends workshop time just to fit the followers to the barrels! It certainly wasn't a case of can't be bothered to fettle them, I had no choice.



It would be interesting to partake of the open day, but not practical from my home in France the week after a race meeting in the South!
 
Last edited:
@Madnorton excellant info Ashley - thank you!

As you’ve been a regular contributor on this forum for many years, I assume you have seen Jim Comstock’s testing of valve train components using a very high frame rate camera.

There are loads of different combinations filmed and posted on his YouTube channel. The differences in behaviour between components is absolutely fascinating.

 
Do I dare to ask if the timing side crankcase was modified with the 1/4" hole on your engine?
 
Last edited:
One very small point about valve spring pressure is that some Combats actually left the factory with coil bound springs .. and according to the itinary of faults listed in Motorcycle Sport Jan 1977 by a senior NVT Marsden Road Engineer .. premature cam wear was not one..

Remember WW2 anyone ? All those high lift cams in high performance Aero engines ? Many issues of course , but premature cam failure as far as Iknow was not one of them ..Well oddly now there is an issue with premature Cam wear in piston engined aircraft of presumably much lesser power . Obviously too simple to suggest that in ww2 engines were run on monograde and now certainly not but it set a train of thought off.. When a monograde oil is hot it thins out - but what about the films that have formed on moving surfaces such as tappets and cam lobes .. as the engine cools then presumably the oil thickens and possibly film strength increases.. With multi grades however some thing else is happening
as the engine cools the oil changes grade , does this effect the film strength and make it thinner and easily wiped
off the cam lobes by the tappets?

One common factor through all these reported cam failures is ,I would wager , the use of multigrade oil , whether that has any bearing of course is another matter . Castrol R anyone?
 
Remember WW2 anyone ? All those high lift cams in high performance Aero engines ? Many issues of course , but premature cam failure as far as Iknow was not one of them ..

Probably because their cam and valve train were not stressed and were designed for durability. These WWII engines were relatively slow lumbering engines designed specifically to turn relatively slow, hour after hour after hour. Their power was usually achieved by manifold boost.


Well oddly now there is an issue with premature Cam wear in piston engined aircraft of presumably much lesser power . Obviously too simple to suggest that in ww2 engines were run on monograde and now certainly not but it set a train of thought off.. When a monograde oil is hot it thins out - but what about the films that have formed on moving surfaces such as tappets and cam lobes .. as the engine cools then presumably the oil thickens and possibly film strength increases.. With multi grades however some thing else is happening
as the engine cools the oil changes grade , does this effect the film strength and make it thinner and easily wiped
off the cam lobes by the tappets?

One common factor through all these reported cam failures is ,I would wager , the use of multigrade oil , whether that has any bearing of course is another matter . Castrol R anyone?

Multi grade oils have been successfully used in our Nortons for nearly half a century without any hint of trouble! Perhaps there is something else going on with this apparent premature wear of aircraft engine cams that I have not heard anything about. You have a source on this as I am interested. I think your alluding to muligrade oil possibly being a cause for premature Norton cam wear is a red herring; especially as you are speculating (wagering) the use of multigrade oil in these apparent premature aircraft cam wear.

Maybe you are confusing things with synthetic oil? From what I garnished from following this thread, I don't think engine oil is the issue in the OP's instance.
 
Last edited:
One common factor through all these reported cam failures is ,I would wager , the use of multigrade oil , whether that has any bearing of course is another matter . Castrol R anyone?

Nope, you lose, mine failed when using a monograde 40 mineral oil! Now using a multigrade synthetic!
 
Who are you asking?

Bike owner

Thanks SteveA ;) BTW

Just asking because, if I got it all, this little hole lowers the oil level in the crankcase, and then the oil splashing by the crank.
 
One very small point about valve spring pressure is that some Combats actually left the factory with coil bound springs .. and according to the itinary of faults listed in Motorcycle Sport Jan 1977 by a senior NVT Marsden Road Engineer .. premature cam wear was not one..

Remember WW2 anyone ? All those high lift cams in high performance Aero engines ? Many issues of course , but premature cam failure as far as Iknow was not one of them ..Well oddly now there is an issue with premature Cam wear in piston engined aircraft of presumably much lesser power . Obviously too simple to suggest that in ww2 engines were run on monograde and now certainly not but it set a train of thought off.. When a monograde oil is hot it thins out - but what about the films that have formed on moving surfaces such as tappets and cam lobes .. as the engine cools then presumably the oil thickens and possibly film strength increases.. With multi grades however some thing else is happening
as the engine cools the oil changes grade , does this effect the film strength and make it thinner and easily wiped
off the cam lobes by the tappets?

One common factor through all these reported cam failures is ,I would wager , the use of multigrade oil , whether that has any bearing of course is another matter . Castrol R anyone?
My combat cam failed and it was running on R40
 
Nope, you lose, mine failed when using a monograde 40 mineral oil! Now using a multigrade synthetic!

well that settled that ... but question why not R ? I know its not practical for a road bike but for racing ?
 
Status
Not open for further replies.
Back
Top