Cam pitting - actual wear, or tolerable quality issue?

[hansaxl]

Dear all,

I recently checked the valve/cam play on my big valve twink. All looks ok, except for slight pitting at the center of one of the cam lobes on the exhaust cam. As said, it is not much, and the hardened surface is intact otherwise. Sorry, no photo available right now.

I have seen many cams of many different cars/motorcycles in my life before. What appeared to be totally standard quality in one make (as said by expert A, specialist in this make) was to be replaced immediately in the other make (according to expert B, specialist for that make). So what do the experts on the twin cam say..? Have Lotus-made new cams always been 100% immaculate or is a slightly lower quality recognised as ok. This all depends on the thickness of the hardened metal, of course...

By the way: I know this is somehow a silly question, especially if I would expect a definite answer. There is too much room for opinion here. I am just interested in seeing the bandwidth of what you guys may think here, ok?

Cheers, and thanks in advance,

Hans

[ardee_selby]

I recently checked the valve/cam play on my big valve twink. All looks ok, except for slight pitting at the center of one of the cam lobes on the exhaust cam. As said, it is not much, and the hardened surface is intact otherwise. Sorry, no photo available right now. Hans

Hans,

Learned folks will, no doubt, be along soon.

In the meantime a question...does the surface of the associated camfollower have any tell-tale signs of a (different) wear pattern?

Richard

[hansaxl]

Hi,

good question..! Answer is Nope, the follower looks ok, no signs of wear (or...: not yet...?)



Cheers, H.

[rgh0]

I have had one standard sprint cam with a casting defect that was a small pin hole in the surface that must have been there from new. This seemed to not cause a problem and I used the cam for many years and it never got worse but it was not to close to the highest loaded points around the nose of the cam.

I have only ever seen problems with original cast iron road road cams on cast iron buckets with long term wear on the nose and not pitting failures. When I have had race cams fail it has normally been due to galling creating pits on the back face of the cam just down from the nose soon after running in, I have learnt now how cirtical the spring loads and material spec and running in procedures are so dont have these problems now anymore.


so if your surface pitting is starting in this area it may be the start of a failure. I would watch it closely for a little while as it is easy to pull the cam cover to check it and if its getting worse replace it.

cheers
Rohan

[hansaxl]

Hi Rohan,

thanks for your note. What you say seems to be the best way to go on from here.

Cheers, Hans