Cam follower Refurb/regrind

The original case hardening depth is easy to see and when re-facing you can be sure that the minimum amount will be ground off. I believe it is actually welded onto the cast-iron body of the cam-follower/tappet. It is visibly a different material.To avoidthe risk of associating myself with any particular Norton spares or engineering establishment Iwill justsay that all 3 of the 'leaders' in the UK offer this service. (The first letters of their names being 'M', 'N' and 'R' !) I live in Southampton and I used an engineeringfirm in Winchester for such work - also used by Norman White, so it comes recommended! They re-bored my barrels and refaced my original radiused cam followers from my 1959 Dommie to make them flat-based, as per 1960 onwards.

As it happens the 3 major players mentioned above would not entertain doing that work! I haven't got the followers to hand but I'd guess thay have around 1/10" hardened depth, so 'flattening' a radiused follower simply means it's the same depth all across the base -like the later types -instead of being thicker in the middle.

You can take off the dunces cap and come out of the corner now!

Previously wrote:

Previously wrote:

Thanks Lionel.

Yes,all that standing around is notgood for the varicose veins.

I hadn't taken the followers out of the barrel, so I was unaware of being able to see the facing material.

If it is as much as 1/10" then I should be lucky to have enough metal left to have them reground. I estimate that there is around 5 thou wear at worst in the centre area of my radiused followers.

I think I will choose to keep the radius profile rather than to flatten them off as this should keep more metal on them.

Just as a matter of interest, If a follower becomesworn centrally,it could be shown that the cam opening period would be extended and the lift will remain the same. The lift curve along with it's acceleration figures will change also. It would be very interesting (Well it would be to me!) to plot the curves for: radiused / flat / worn followers using a standard camshaft.

My prediction is that a well rounded-with-wear follower (not one that has a sharp centre worn dip)would have:

1) The same lift.

2) Longer lift angle.

3)faster acceleration rates.

Makes you think is it worth regriding the cams anyway!...LOL

Yes tune your engine....fit worn out cam followers!

Thanks for the recommendations too Lionel, hmmmm M, N, And R....now who can these be then....

ATB

Les H

CORRECTION: SHOULD HAVE SAID....makes you think; is it worth re-grinding theCAM FOLLOWERS anyway ...LOL

Hi again Les,

Nope, you're wrong about flat-based versus radiused cam followers!I believeNorton brought them out originally for the SS models, together with the SS (X1 & X2) camshaft,to give "sports" performance. From about 1960 they fitted them to all models. (Earlier with the export Manxman)

A radiused base will give a shorter dwell angle and the valves will close quicker. I think it's worth having them refaced but the cam needs to be in very good condition. Les Emery will probably tell you that you should get a new camshaft if you have new or refaced cam-followers! It seems to be cheaper to have a camshaft re-engineered than it is to buy a new one.

Cheers, Lionel

Hi Les, yes you are right and I was wrong to say you were wrong! I misread your posting.

First - re: the case hardening depth. There's plenty of meat there to permit grinding the bases flat, as per 1960 onwards, and it supposedly gives an improved performance. I don't know how much metal they remove for radiused followers, or even if they do them at all! I haven't made any enquiries on that so I'm in the dark. Bear in mind that only flat-based followers have been used since 1960.

With new followers and a new cam there is still no guarantee that the meeting faces will have a perfect and even contact as there are too many variables. It relies on the tappet bases to be ground precisely at right angles to the tunnel and the camshaft to be running precisely at right angles to that! I think that's being a bit optimistic to say the least! Even a couple of thou off will result in lopsided contact. To check it with engineer's blue is too tedious to even contemplate as the full head, pushrods barrel and the crankcase with camshaft installed would have to be assembled - just for a test - THEN dismantled! Phew!! I think not!

So, my theory is that there is too much worry whether the cam and tappets are going to engage spot-on if they are not both new or refaced. I am thinking of getting my camshaft "refaced" as it's cheaper than buying a new one but I'm not sure if anyone has the data for making it a "QR" profile, as per my original 1959 99 'Special'. (So named by John Hudson)

Cheers, Lionel

Previously wrote:

Hi Lionel.

Thanks for coming back, but it seems you may have misunderstood my reply to you. (Please read again)

I was not saying that radiused followers gave long duration, I am totally aware that the flat followers give longer duration.

I was just saying that to keepmy ones standard and also to keep more metal on them I would simply have them ground to the original radiused profile.

I then went on and suggested (with some tongue in cheek) that if cam followers became worn to a CONCAVE SHAPE, ie: worn pasta flat contact surface....to become a well rounded HOLLOW, then the opening duration would even exceedthat of flat followers and hence give even LONGER timing....do you see what I mean?

It would then seem unnecessary to worry about getting them back to a flat shape contact surface, AS LONG as the wear was well rounded and did not have a sharp indent that could NOT track the base circle of the cam. If the wear hollow is too sharp, the follower will not track the cam base circle and result in a lower lift.

I have also read that one should not mix old and new cams and followers, and I can see why. As each one picks up each others wear profile, putting either up against a new truly flat width-wise profile will result in extremely high pressures and wear rates on the new surface.

So I hope you can now agree I was not wrong?

Les H