Camshaft Identification

[jono]

I'm refreshing my engine primarily to cure oil leaks after doing 15k miles since a full rebuild.

I've stripped the head to decoke and do some other jobs and have noticed that some of the cam lobes are pitted on the ramp and nose. The cams are SE re profiled to QED360 spec.

I noticed this pitting not long after the engine was first started but it does not appear to have got any worse - should I be worried about it? The buckets look okay and there is no measurable height difference between the unaffected lobes and those which are pitted. The engine runs well.

This brings me on to a second question - I have a pair of cams which came from a low mileage dry sumped tall block TC which was built new by Vegantune in 1979 for a factory supplied Caterham Seven and I may fit these cams if the pitted ones are a no no. The cams are marked MC 25011 then 26 E 351 then 'D' between the bearing journal and number 4 lobe. I've measured the lift at 0.360.

The QED profile cams measure at .0.355 lift but the lobe shape is quite different - much more pointy and a flatter ramp than the Vegantune cams and a narrower nose. I've attached a photo with the Vegan lobe on the left and the QED 360 on the right.

My understanding is that the QED 360 is a sprint cam in all but name so my guess is the vegatune cam is something other than a sprint cam due to the different lobe shape.

Has anyone any suggestion as to what profile this might be and what sort of characteristics it might have? The cams are in superb condition.

Cheers

Jon

[jono]

Guys,

Could someone post up a pic of a sprint can lobe for comparative purposes?

Jon

[rgh0]

Photo below is original sprint cam on a 1.15 inch standard base circle. The larger the base circle the broader the lobe will appear. So the two cams you have may be the same timing on a different base circle.

Pitting due to micro welding in the cam surface around the nose during or soon after initial running in is normally due to inadequate lubrication on initial startup, poor running in procedure, excessive valve spring loads or poor surface finish on cams or followers (maybe due to reuse of second hand followers). It is more common in high lift , high acceleration race cams but certainly possible in standard cams. You may be lucky and the cam has now run in OK and no further damage will occur but their will probably be micro cracking around the pits in the cam surface and overtime you could have further surface failure. I personally would not take the risk and i would replace the cams and I would try to understand the cause of the failure or at least ensure all the right precautions are taken with the next set of cams

cheers
Rohan

[nmauduit]

I noticed this pitting not long after the engine was first started but it does not appear to have got any worse - should I be worried about it? The buckets look okay and there is no measurable height difference between the unaffected lobes and those which are pitted. The engine runs well.

regarding pitting/discoloration on camshaft bearing surfaces, you may want to inspect closely the matching surfaces for smoothness or other indication of probable cause.

[jono]

Many thanks for your comments on this and, Rohan, what you say makes perfect sense now I think about it with the base circle having been reduced down to 1" on the reprofiled cams.

My suspicion is that this could be my own fault for not bedding the cams in properly initially as I did have it idling for some time on first start up and it sat for couple of years before it was fired up. I now put Redline assembly lube on all high pressure parts when I re assemble an engine.

I also know that my engine builder used the old buckets and I doubt that he lapped them first - one of many errors I have since discovered.

I'll have a think about this but may run with the pitted cams for some more miles and keep a close eye on them while I save up for some new ones!

Cheers again.

Jon