Camshaft run in procedure and cam wear

I am anything but an expert, but given the known issue with cam lobes wearing away I wonder what procedure forum members follow when they are running in a new camshaft? My understanding from various sources on the web (including camshaft manufacturers) is that it is critical that the first start with a new camshaft should involve running the engine for 30 minutes or so with the revs varying between 2500 and 3000rpm (never left to idle).
From what I understand this run in procedure work hardens the camshaft lobes and prevents premature wear, so it would seem at least possible that there is a link between premature camshaft wear and this run in procedure not being followed. The reason for running the engine at 2500 to 3000 rpm is apparently to reduce the force the valve springs apply to the peak of the lobes.
As I mentioned above, I claim no expertise at all, but I did recently look at a Norton cam that had one lobe almost worn away. The surface of an unworn lobe on the cam was easily marked by a file on the base circle, but impossible to mark at the peak of the lobe, which suggested to me that the peak had work hardened - which does suggest that perhaps proper break in, that does allow initial work hardening to occur correctly, might be linked to long term camshaft life.

Something like... this:



Most likely not from the startup. This bike had a few miles on it but good chance that for a while a bunch of low zinc oil. Or just a suspect cam.

Oouch!

Ewwww.
Ouchy-Ewww.

You want to hear the crazy part? I rode that from NC to Barber one year, about 1000 miles. It was a little... sluggish.

yeah i have one like that on the shelf....

MK3 Steel cam? if so, not unusual.

Madnorton said:

MK3 Steel cam? if so, not unusual.

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Nope. 73 850.

There is no such thing as work hardening on a case hardened cam -or any Norton cam that I am aware of.

You run it at 3000 rpm to allow a bit of hydrodynamic lubrication to prevent metal to metal contact until the microscopic peaks are worn off.

I would be willing to bet the follower on that particular lobe is soft which will cause the lobe to fail.

The base circle on the cam is always softer. It does not cool as fast as the lobes during the hardening process so it stays soft. Jim

Thanks Jim. Presumably the car camshafts use a different material or initial hardness.

I don't know anything at all about camshaft hardness BUT the procedure posted by the OP is the only way to break in a camshaft. If it is not done as described, a camshaft can be totally ruined in very little time - easily in 1000 miles and I have seen some cams that were allegedly destroyed in a week of normal operation due to improper break-in BUT that particular claim was hearsay, not an actual observation on my part. I have personally seen cams that didn't make it 1000 miles because the installer thought he knew more than the cam maker about installation. Usually that took the form of putting tons of assembly grease on the cam/lifters and figuring that was good enough and then just starting the engine and letting it idle while he futzed around with timing, etc...

We always set the static timing by hand at TDC (engine not running) then start it, IMMEDIATELY increase RPM to 2800-3000 and leave it there for 30 minutes. Static timing at TDC makes an engine easy to start. You can adjust the timing later or even during cam break in as long as you ensure RPM never drops below 2500.

Is this process really practical with a fully rebuilt motor???? Rebored and crank ground
Not to mention the lack of cooling at 2500rpm for 30 minutes..... unfortunately we don't all have rolling roads available with cooling fans

That's a reasonable concern but I am not aware of any other process that will ensure proper cam break-in.

FWIW, MAYBE there are different break-in methods for some "modern materials" camshafts but if so, do EXACTLY what the cam-maker instructs.

A water hose/fine spray on the fins will take care of the cooling issue - messy if done in the garage!

this procedure should be done on standard Norton factory cams ?

olympus said:

Is this process really practical with a fully rebuilt motor???? Rebored and crank ground
Not to mention the lack of cooling at 2500rpm for 30 minutes..... unfortunately we don't all have rolling roads available with cooling fans

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That first 30 mins doesn’t have to be stationary.

I’d say to start the eg one and run very briefly at this end revs then switch it off. Then you can check for leaks, loose fixings, etc. And if you have a composite HG, it should,be left to cool and re torqued.

Then, the 30 mins and 2,500-3,000 rpm can be done on the road.

The cam definitely needs run in time of 20 to 30 minutes at engine speeds over 2500 rpm. This is with any new cam -stock or otherwise.

Use a cooling fan or ride the bike to keep the temp under control. Carpet drying fans are cheap.

This process will not hurt the crank or pistons at all -as long as the temperature is kept in check.

Starting a fresh engine with a new cam and allowing it to idle even for a minute is likely to cause early cam death.

I have seen a new cam in car engines mortally damaged by excessive cranking when the guy couldn't figure out why it wouldn't start. [the pushrods were slightly too long] And the thoroughly scuffed cam was still covered with assembly lube.

Yep, Quick starting was the reason we (I) always set the engine timing to 0 (TDC) prior to the first start...though that wouldn't have helped with the wrong pushrod length!

comnoz said:

The cam definitely needs run in time of 20 to 30 minutes at engine speeds over 2500 rpm. This is with any new cam -stock or otherwise.

Use a cooling fan or ride the bike to keep the temp under control. Carpet drying fans are cheap.

This process will not hurt the crank or pistons at all -as long as the temperature is kept in check.

Starting a fresh engine with a new cam and allowing it to idle even for a minute is likely to cause early cam death.

I have seen a new cam in car engines mortally damaged by excessive cranking when the guy couldn't figure out why it wouldn't start. [the pushrods were slightly too long] And the thoroughly scuffed cam was still covered with assembly lube.

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So how do camshafts in new cars/motorcycles survive? I doubt that many owners of new vehicles follow that procedure.
Do the vehicle manufacturers follow some procedure beforehand?

I witnessed new cars come off the assembly line at Oldsmobile in the 1970's. They revved them and squealed the tires in the building and out the door

Ibex said:

So how do camshafts in new cars/motorcycles survive? I doubt that many owners of new vehicles follow that procedure.
Do the vehicle manufacturers follow some procedure beforehand?

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Most new engines get hot or cold tested at quite high rpm at the end of the engine assembly line.

Then, when fitted to a car, at the end of the car assembly line, they go through a ‘function test’ which involves running at reasonably high rpm.

Then they get driven around by delivery guys etc, most of whom squeal the tyres everywhere!

Then, eventually, the engine is in the hands of a customer, and today at least, most people pay very little attention to running in a part from ‘not thrashing a new engine’ so a new engine gets put almost straight into ‘normal’ use.

I’d guess it’s pretty much the same for a new motorcycle too.

So all in all, pretty ideal for the cam I’d say.

It’s just us shed builders who have been brought up (wrongly) to think that a new engine needs treating with Kidd gloves!

We’re our own worst enemies it seems...