New cam followers on old camshaft

[mini_surfari]

Had a mare, and a few cam followers got mixed up! So don’t want to put them back in now.

Are we ok to put new followers on an old camshaft? Only ever done new and new before.

Cheers!

[5portsrock]

Yes, that's fine

[Peter Laidler]

I was just about to come on board and say the opposite......, with reservations! Based on nothing more that good engineering principles/practices. It's a bit like matching bearings or articulating ball joints....., you know the sort of thing. Once they've run together as matched sets, my engineers head tells me no. But never heard anything contrary to cam followers on shafts which are constantly drenched in oil.

I hope someone will come on board with a reason and put me right. Have a good new year everyone......

[Alex]

New followers with an old camshaft is fine - I've done it many times.

[iain1967s]

Hi Peter,

I think the main reason not to reuse old followers mismatched from their original location, is that the cam lobes and follower faces will have bedded in to match each other at the angle ground into the follower.

[Contrary to popular belief, the face of cam followers is not flat; it is ground convex - both to apply a rotation on the follower, and a rearward thrust to the camshaft]

My experience is that face of new chilled iron followers have a deliberately rough surface finish that helps to hold an oil film more effectively, which is needed until they can bed in to match the cam lobes.

In this case, even more importantly as the old camshaft lobes will already have been work-hardened and smooth, so all the wear should occur on the new followers.

So, old cam with new followers, no problem.

[Ronnie]

If you are concerned check the contact area's with micrometer blue (as Peter often states engineering principals)

[Spider]

Not a good idea. They do bed in to each other. You might get away with it sometimes, but for the cost of new decent followers, I won't try it on.

I equate it to running new rings in an old bore.

[mini_surfari]

A real mixed bag there, really am kicking myself the got mixed up but is what it is

I was hoping I could get away with new followers, some
Cam lube and then bed them in with normal procedure.

[5portsrock]

Mixed bag? All bar one says new followers on old cam or am I missing something

[CooperTune]

My approach would be to closely inspect the ramps on cam lobes. If there is any pitting on ramps or over the nose discard the cam. Next is to check the face of all lifters. This is best done with a quality straight edge. A good lifter should be high in the center with no pitting. If light is visible in the center the lifter is no good. I have always considered it like walking along a ditch bank. Lifters are ground on the face with a 70-inch radius. This allows the lifter to bare on the center of the lobe slightly off center making the lifter spin. Once the lifter face becomes concave it begins riding the edge of lobe causing the ramps to pit and crumble. If the cam lobes are in good shape, I see no reason new lifters should not extend the service life. Steve (CTR)

[mini_surfari]

Mixed bag? All bar one says new followers on old cam or am I missing something

Well I read spiders reply as a no, unless I’ve miss understood him.

Either way, the followers are currently on their way to Keith Calver, to reface them to the correct convex shape.

[timmy201]

Mixed bag? All bar one says new followers on old cam or am I missing something

Well I read spiders reply as a no, unless I’ve miss understood him.

Either way, the followers are currently on their way to Keith Calver, to reface them to the correct convex shape.

I think Spider means don’t mismatch used followers in a different spot from where they were running. And new followers and used cam is ok

[winabbey]

I think Spider means don’t mismatch used followers in a different spot from where they were running. And new followers and used cam is ok

I agree.

[mini_surfari]

My Mistake, apologies!

As I say, hopefully they’ll be back in a week or so, and the engine can go back together…

[Exminiman]

My Mistake, apologies!

As I say, hopefully they’ll be back in a week or so, and the engine can go back together…

Just out of interest, why did you not buy new followers from Keith ?

[mini_surfari]

My Mistake, apologies!

As I say, hopefully they’ll be back in a week or so, and the engine can go back together…

Just out of interest, why did you not buy new followers from Keith ?

Well I was going to, but after speaking with him he suggested refacing my originals as they aren’t badly worn (low mileage engine). £2+ vat each to reface.

I would expect the originals will be a better quality material than the majority of new followers available… not that I’ve had any specific problems with the other engines I’ve built using new, but you see my thoughts.

[Exminiman]

Interesting, TBH I had no idea you could get them refaced easily…

[mini_surfari]

I believe Keith imported the machine from Australia about 10 years ago to do them with the correct radius, just from reading other threads on forums.

[Spider]

Well I read spiders reply as a no, unless I’ve miss understood him.

Either way, the followers are currently on their way to Keith Calver, to reface them to the correct convex shape.

I think Spider means don’t mismatch used followers in a different spot from where they were running. And new followers and used cam is ok
[/quote]

Sorry if my post wasn't clear.

As Tim suggests, in my view and experience I've found it satisfactory to run new cam followers on a used cam however the caveat here is that the cam does need to be in good condition and not worn. I've found the factory cams up to around 84-ish to be of very high quality, after that, they didn't seem to be ground correctly (or done sloppy) and were softer than the earlier cams.

I also suggest that running used cam followers was not a good idea.

The pre-84 cams that I referred to were hardened on the lobes and journals. This is where you need to be careful with regrinds as all too often the material removed from grinding will go beyond the boundary layer and you'll be in the softer core steel. Very few Grinders re-harden them after grinding.

Likewise, you also need to be very careful with reground cam followers. The original factory ones were chilled iron and had a face hardness of 62 - 64 Rc. Refacing them will get in to softer material, but in any event, re-facing cam followers is only ever intended to be a clean up of of a good used follower. If the follower is scored, has not been rotating or pitted, then it's best to discard it as by the time it's re-ground, it won't have a hard enough face. They should also be tested for hardness following re-facing. The other issue with re-facing is how many times has it been re-faced previously ?

The 'action' of the lobes and followers is that of rolling (bearing) elements. The Cam Lobes have (or should have !!!) a taper on them, with the 'tall side' on the Sprocket end.



That drawing, while exaggerated to illustrate the point, also shows why the face of the followers are dome shaped. If memory serves, the original factory followers are ground on a 36" radii.

The combination of the lobe taper and dome faced follower causes the follower to rotate as the cam rotates, like a bearing element. It also cause the Cam to 'thrust' towards the front end of the engine. This is why the Cam Thrust Plate only has babbit material on the back side.

If I can post up a Drawing that Doug kindly posted here a while back, you can see that the babbit is only on one face;-



This too is why it's 100% pointless going to the nth setting Cam End Float. It only need have a minimum 0.003" and a maximum of what ever you like.

Just coming back to having follower re-faced and breaking through their hardness boundary layer, here's an extreme example;-



It's clear that it had been rotating but was far too soft. Needless to say, it chewed out the cam.

My 'go to' cam followers for a long while now have been those from APT in the US. When I haven't been able to get them, Iskys are the next pick. Both are very good quality.

[Polarsilver]

Gents, so you worry about the Cam Follower contact surface to the cam ..but dont seem to worry about the inner surface that the Push Rod contacts ..me i look at the wear at the push rod end & that decides if i re-use the old Cam Followers .. maybe it just me