Worn PW3 cam

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Worn PW3 cam
Well speaking for myself, drive side.
Stock 850 with less than 30k on the clock
Pete
 
Nope, left inlet lobe on mine!

And no, it doesn't idle at 1000 rpm, ever! Gets blipped between 2 to 3 when waiting in the holding area for a race to go to the grid.

Does that go on for too long?, yes always! Races are often held too long, but it was ever thus, no change there.
 
Right hand exhaust on mine, left inlet usually the worst on old MK3 cams I have swapped out
As for spring pressure it is not easy to check, statically yes, but but at the range we use them a little harder.
The spring pressure on the worn lobe I am very much expecting to be non-existent in relative terms as the valve tip and the adjuster are unmarked.
As for zinc, not sure if my cheap oil has it it in, may do, but what quantity I am not sure.
 
Only ever had one cam lobe wear out and that was the left hand exhaust lobe on a combat running on R40
The other 3 were fine
 
Madnorton said:
Right hand exhaust on mine, left inlet usually the worst on old MK3 cams I have swapped out
As for spring pressure it is not easy to check, statically yes, but but at the range we use them a little harder.
The spring pressure on the worn lobe I am very much expecting to be non-existent in relative terms as the valve tip and the adjuster are unmarked.
As for zinc, not sure if my cheap oil has it it in, may do, but what quantity I am not sure.
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A static test will show if a spring has gone bad. There are various spring pressure tester devices available. Most test the spring when it is removed , so you need to know installed height.
I've used a homemade rig that tests pressure with spring installed.
That was an excellent tool.
 
worntorn said:
I've used a homemade rig that tests pressure with spring installed.
That was an excellent tool
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Was this tool used with the head on the benk or on the head with engine in the frame? Do you have some photo you can post?
 
It was used with the head on.
Sorry, I don't have any photos.
It used a common spring scale for measurement.
Another engine builder friend saw it and said " that's a joke, you can't use that crude thing to measure seat pressure. Take things apart and use my proper hydraulic tester"

So I did and the result was identical +- 3 lbs.:)
 
There are several problems with the original nort cam setup (and there are solutions). The first is the high stress high wear pointy nose geometry design for flat lifters (left). Rounder lobes designed for radiused lifters are on the right (custom cam).
Worn PW3 cam


The 2nd is the hit or miss oiling. Oil comes down the pushrod tunnels to the lifters and runs down the vertically chamfered corner of the stock lifter where it lands between the lobes - not on top of each lobe. The oil in the horizontal cam tunnel may be too shallow for the cam lobes to pick it up. Its possible that some cam lobes are starving of oil.

Below is a custom tappet block with oil drain holes that line up directly over each lobe so that each lobe gets wet as it turns counterclockwise into the lifter.
Worn PW3 cam


Cams designed for flat lifters can use a slightly radiused cam but a cam designed for radiused lifters has a rounder smoother nose and the lifter radius is all the way down to 1-1/8". BSA lifters fit the tappet blocks shown above but stock lifters can be ground to 1-1/8" radius as below but you don't get the ideally located oiling drain holes (also works for early cut corner stock lifters).
Worn PW3 cam


Stock cam can last a long time and I have had good luck (except for one). But the cams for radius geometry lifters generally last longer.
 
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Madnorton said:
Stellite has never been used to tip the followers, Delcrome has which was produced by the firm called Stellite way back who made various cobalt and iron hard faced materials and alloys and no surprise a material actually called Stellite. Current supplier of Delcrome is Delero in Europe, a subsidiary of a US company. Stellite and Delcrome are two very different materials, one iron based, one cobalt based, they can suit the same function but at different temperatures and Stellite has a better resistance to corrosion obviously. The other major major difference is cost, Cobalt is traded on the metal markets in lbs, not tonnes. Deloro also supply and apply coatings, and don't seem to need to advise coating Delcrome.
The answer to the cam failure is in post 1 on page 1 - the fact that the coated followers were not affected is typical of coating application. It will provide a very good sliding surface, but not one that can sustain impact as well - yes, it hard, but that is a function of the coating being able to reduce friction, the hardness of a coating when used on a cam is not what is being asked for. ask those that coat why this is and they should tell you, not sell to you - ever wondered what happens to the substrate under the interface of the coating when being applied. No doubt some can work out why the Delcrome will take a coating and survive and the cam does not. If you have a cam in constant contact with the cam follower then a coating would be ideal. The same problem has been around for ages in the grinding industry when grinding hardened bearing surfaces, but they will avoid it.
Beehive springs - excellent piece of kit, but you just can't use any beehive spring. The move from nested springs to single spring is the clue - ever wondered why there are two springs, not one when Norton could have used one, the second spring has another function other than get the poundage right to control the valve correctly. The low revivng engines we use are not even a challenge to spring makers these days.
It is also no secret who manufacturers these chill cast cams, do you honestly think that they buy just 50 blanks and grind them, no, more thousands at a time. Considering this is about one type of chilled cam issue, then further questions other than chill cast need to be queried. Considering the number of cams sold, inc PW3 that are fitted by many engine builders worldwide and home mechanics (some of whom are well over 26K miles on there PW3's) would quite clearly indicate that there is not an issue with the chill cast cams. Those that retail PW3 cams, maybe a surprise to some, but actual sell more than one every now and then. If there was an issue with chill cast, do you honestly think that any of them would carny on using it, no it would be substituted, so make your own minds up.
Coatings are excellent when used in the correct place, those that apply coatings should advise accordingly on application and suitability of base material and its pre-coat state and post coat state.
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A couple of points here.
1. I have never heard of Delchrome.
2. Norton workshop manuals specifically refer to the lifters as being "stellite tipped". Why the discrepancy?
3. Andover Norton continually advertise that their parts are all made "to original apecification".
4. When did the pad change from stellite to Delchrome?

So, what is the truth of the matter?
You still didn't answer the question about my cam lasting 6 times longer than any other failed cam noted, whilst still being an "inappropriate coating" use.
 
jseng1 said:
There are several problems with the original nort cam setup (and there are solutions). The first is the high stress high wear pointy nose geometry design for flat lifters
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I must still be missing something............
earlier you said cam wear was caused from stiff valve springs, now, it's flat lifters and / or oil starvation - which is it?

I don't think there will ever be a chance of fixing the problem of cam wear IF a direct cause cannot be determined.
 
Stellite has never been used, it is a group of materials and the trade name of the company that produced it at the time. Delcrome was made by the company called Stellite, then Kennametal and now Deloro, part of the collection of companies owned by Madison Group.

I doubt if the workshop manual was ever checked, if it was many other points would be rectified, the material spec says Stellite Delcrome, the company name at the time and the spec of material needed. Stellite has no great hardness gain over Delcrome, just that Stellite would be used in environments where Delcrome can not be used. Cobalt was always expensive, but now it is astronomically so, especially in the last couple of years, so now the choice would most probably run along the lines of Delcrome, Triballoy type material and then Stellite.

Your cam may have lasted the same amount of time had it not been coated, we will never know. If coating cams was the be all and end all solution, then we would make them from EN16 and the like cheaply and then coat them, the're not, ever considered why, likewise cam grinders would automatically coat all their cams, they don't. Coatings are ideal on some cams but not all.

Study the two metals and then it becomes quite clear why the followers survived better when a coating is applied. It might be space age technology coating, but not rocket science to understand what happens when the coating is applied. From all this it is quite clear that your coating never failed, it was applied correctly, but used in an incorrect application.

My cam has failed at just over 20K miles, no, it is not chill cast, but steel, but one lobe has failed. Irrespective of whether it is steel or chill cast, then I believe looking at it something else caused that failure, and had would have done no matter what cam was fitted.
 
Mark said:
I must still be missing something............
earlier you said cam wear was caused from stiff valve springs, now, it's flat lifters and / or oil starvation - which is it?

I don't think there will ever be a chance of fixing the problem of cam wear IF a direct cause cannot be determined.
Click to expand...


There are several problems with the stock Norton cam setup as described in previous posts. If you just fix one problem you are still stuck with the others.

Don't limit yourself by looking for just one problem when its a combination of problems that is causing Norton cam wear.

The problems with Norton cam wear have already been addressed as described with photos three posts above and will outlast the stock setup by a long shot. Putting on stiffer springs than necessary or bringing back any of the problems that were addressed would just cause unwanted cam wear.
 
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comnoz said:
Because there is such a small amount of oil that travels down the pushrod tubes from the exhaust rockers that it is not worth it. The cam gets it's oil from what is thrown off the rod bearings. Comnoz
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Jim, do you have any opinion on whether this leaves any lobes having less oil than others? And / or, from the dozens of worn cams you must have seen, do you see any trend as to any one lobe being the one that fails most frequently?
 
Fast Eddie said:
Jim, do you have any opinion on whether this leaves any lobes having less oil than others? And / or, from the dozens of worn cams you must have seen, do you see any trend as to any one lobe being the one that fails most frequently?
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What about a difference between pre and post combat engines ? Wondered if the breathing arrangement creates a low pressure area in the vicinity of the cam helping more of the oil fling or vapour makes its way onto the lobes?
 
Fast Eddie said:
Jim, do you have any opinion on whether this leaves any lobes having less oil than others? And / or, from the dozens of worn cams you must have seen, do you see any trend as to any one lobe being the one that fails most frequently?
Click to expand...

No, I haven't seen any one lobe failing more often than others.

I don't think lack of oil is a problem. I do think improper oil is sometimes a problem.

I am working on a way to monitor the pressure of the lifter against the cam in real time. I think the reason for some failures will be seen there.
I just need to purchase a couple more pieces of hardware, anyone have an analogue load cell amp they want to contribute to the cause. Comnoz
 
oldmikew said:
What about a difference between pre and post combat engines ? Wondered if the breathing arrangement creates a low pressure area in the vicinity of the cam helping more of the oil fling or vapour makes its way onto the lobes?
Click to expand...

I have definitely seen more Combat cam failures than standard cam failures.

I suspect it is more likely due to the fact that stock springs have a very short lifespan when used on a Combat cam, plus the cam has more aggressive ramps.

One thing for sure, regardless of the type of cam, the more aggressive the grind is, the faster the cam and valvetrain is going to wear out.
 
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