Worn PW3 cam

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Mr. Rick said:
Forgive me, I don't quite follow. You had 3 failures in 6700 miles with AN PW3's, then used a coating and next failure (Hemmings) took 26,000 to happen?
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No, read the thread. Those are the ones I know about. Two on here and another local one. Mine did 26,000 miles.
 
26 k and all that damage to the rest of the engine doesn't sound great, coating or no coating.
I like Stellite !

Glen
 
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A photo of the failed cam would help - and it would give us a clue about the coating. I know that SRM tried to make some hardened lifters without stellite pads and substituted DLC coating - it didn't pass testing.
 
worntorn said:
26 k and all that damage to the rest of the engine doesn't sound great, coating or no coating.
I like Stellite !

Glen
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So, what you are saying is that the other guys won't have the same engine problems as me because they did less miles than me? The one at 1500 miles had lobes more badly worn than mine! And all that camsnaft material didn't end up in his bearings and crank?
 
Ken,
prior to engine strip down,
Did you notice any prelude to bad thing happening like big chunks on the magnetic pickup on the drain plug during oil changes. Did you have your oil filter analyzed? IE. pulled apart to investigate?
Regards,
Thomas
 
Fullauto said:
So, what you are saying is that the other guys won't have the same engine problems as me because they did less miles than me? The one at 1500 miles had lobes more badly worn than mine! And all that camsnaft material didn't end up in his bearings and crank?
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No, I'm saying none of those outcomes are acceptable.
Forget secret cam coatings , go directly to Stellite or similar hard weld .Which is what you are going to receive.
 
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While not a Norton cam, this is a stellite welded cam that failed in about 3000 miles. The cam lobe dips into an oil bath on every rotation
Worn PW3 cam

Worn PW3 cam
 
Most Vincents today run stellited cams and followers. Use of stellite there put an end to early cam wear. Lots have done over 100,000 miles, rebuilt the engine and put the cams and followers back in untouched, needing nothing.
It is a tricky process however and if not done correctly Stellite will crack.
We're lucky that there is a Specialist in the UK who has the process down pat.

In reading about the Web Cam hard weld process, it sounds similar to Stellite . Web Cam has their own preferred alloy for the hard weld.

Glen
 
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I think Comnoz demonstrated that valve springs that are too weak can give poor control and the loft and fret that this allows can pound the stelite, causes cracks and another similar issues.

To some (like me) this was news, as I’d always been a fan of the lightest possible springs. This may have small advantages (ie less power loss) but can cause what might seem like counter intuitive wear issues.
 
That was John McDougall's belief as well.
Valve springs that allow the valve to float do lots of damage.
Better to put up with a bit higher seat pressure and maintain control.
And use RD or some other high grade spring, not just any old valve spring. Some are made of poor material and lose a great deal of seat pressure with use


Glen
 
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I got a good demo of what happens with low spring pressure in the last batch of heads I did.

It was a Combat head that had been rebuilt and assembled without the insulating washers around 5000 miles ago. The springs looked like originals.

The seat pressure was less than 40lbs and the valves had receded into the seats to the point where there was no more adjustment left. One exhaust valve was missing a chunk. That's when it quit running on one cylinder.
The cam which was a NOS Combat cam when the motor was assembled was pitted and the lifters had a deep wear mark across the center. Jim
 
Just a thought but back in the day all 750s assembled down at Andover were sent for a quick thrash round the Thruxton circuit... which might have helped give the camshaft and lifters an opportunity to 'work harden' . Soft cams came an issue when production was transfered to Wolverhampton . Note according to the manual ,the steel used throughout Commando production 750 and 850 alike was EN 34 . Am not sure when stellite facing of the followers was introduced , but if the followers are harder than the cam lobes , then with weak springs the trailing cam lobes are going to get a hard time .
 
In the case of the failed cam photo that I posted above, the stellite welding and grinding was done by a very experienced camshaft grinding firm. The followers were also refaced and reground to a different radius and offset than was original, but by a different firm. The followers were however refaced with Castolin Eutecbor 9000 hard facing brazing alloy containing stellite, tungsten etc. Quoted RC55 – 62 which is similar to the stellite weld and recommended by the manufacturer for the purpose. There was no sign of wear on the followers, just a polish. The followers generally wear much more quickly than the cam.

The Eutecbor hardface brazing is however more difficult to grind than stellite.

The valve is 1.75” and valve spring seat pressure of 130lbs.

The cam is set to run in a bath so that the lobe dips into oil every rotation. The oil bath does however drain when the engine is stopped and would take some running to fill after each start.

I would love to know the cause.

ando
 
ando said:
In the case of the failed cam photo that I posted above, the stellite welding and grinding was done by a very experienced camshaft grinding firm. The followers were also refaced and reground to a different radius and offset than was original, but by a different firm. The followers were however refaced with Castolin Eutecbor 9000 hard facing brazing alloy containing stellite, tungsten etc. Quoted RC55 – 62 which is similar to the stellite weld and recommended by the manufacturer for the purpose. There was no sign of wear on the followers, just a polish. The followers generally wear much more quickly than the cam.

The Eutecbor hardface brazing is however more difficult to grind than stellite.

The valve is 1.75” and valve spring seat pressure of 130lbs.

The cam is set to run in a bath so that the lobe dips into oil every rotation. The oil bath does however drain when the engine is stopped and would take some running to fill after each start.

I would love to know the cause.
ando
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When I see scuffing on the lifting side of the lobe I look for lubrication problems or bad break-in procedure.

When I see pitting and flaking near the peak of the lobe I suspect valve train control problems -bad springs, springs not matched to the cam grind or a cam grind not suitable for the valve train. Jim

PS, of course a poor weld job could be the problem also.
 
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Thanks Jim. Welding was done by Franklin Cams NZ and the stellite was applied with a hydrogen water torch. Considering their experience I would doubt a bad weld, although that would give me peace of mind. http://www.camshafts.co.nz/AboutUs.aspx

Other cams that I have had done by them are all satisfactory.

The valve springs that I am using are aftermarket beehive springs for an LS1 GM engine and are shimmed to give a little more seat pressure. The cam was covered liberally with run in lubricant as supplied by Franklin. Maximum revs is around 7250 although the engine revs willingly well beyond that. Engine is a short stroke Ariel single and the cam is the factory competition cam with slightly longer ramps. The valve timing measured at .050” lift is 39 68 59 44 (or 39 68 70 30 with an offset foot exhaust follower) which is fairly hot. So valve train control is looking like the problem. I was about to fit a larger 1.85” inlet valve, so I may have to rethink that as well as the valve springs that I am using. Sorry about hijacking the thread a little.

ando
 
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