I'd say 1mm dish on the follower is too much really, OK, the hydraulics will take up a lot of slack but that much would be pushing it. Is it just the one? I've got a set that I took out of mine and fitted new ones but only 3 or 4 had any appreciable wear. I can bung a couple in the post if you like.

It's only a couple that are badly dished that I can see. The cam lobes themselves look not too bad, surprisingly.

The gasket on the passenger side is okay, but having both heads off will let me clean all the oily mud and pondweed out and lap the valves in, which might make two or three metric brake catpower of an improvement.

Surely the issue is the two parts wear together... If you fit new followers to an old used cam, the worn cam will ruin the new followers in short order?

This is the usual problem with engines, once you crack it open its a slippery slope down the rabbit warren of doom.

I suspect that's a bit "theoretical". The camshaft is probably going to be coming out in the next few months anyway if it's that bad.

yeh, but if you fit new followers to the worn cam, then fit a new cam to the new followers a few months later, you'll likely just result in writing it all off, as the old cam will chew up the new followers, then the new chewed up followers will ruin the new cam...

Either do the cam now along with the followers, or leave it all alone, IMO

No, there are only a couple of badly dished followers just now. What I am considering doing is sticking some not-quite-so-bad followers in for now and replacing the whole damn lot in a few paycheque's time.

While "everyone knows" it'll chew the camshaft up in the first ten seconds of running the engine, in practice it doesn't make a bit of difference. Same with pushrods - the TB for replacing miscast rockers says to replace the pushrods only if they're damaged. If they're fine, leave them alone. But surely the ends of the pushrods have worn to fit the old rockers, so you'd need to replace the pushrods too, right? And then the tappets would have worn to fit the pushrods, so you'd replace those, and the camshaft, and cam chain, and so on and so on.

The theory is that if the followers are dished then the lobes on the cam will no longer be flat but curved so putting a new follower in will mean only the centre of the lobe will be in contact with it. Then it's a toss up whether it wears the new follower so it is dished the same as the one that came out or wears the end on the cam lobe to get it flat again. Thinking about it, there's a good argument for fitting Britpart followers, you'd never wear a camshaft out......

As i understand it, the grind on the cam lobes is such that the follower is supposed to rotate in the bore. basically its not perfectly flat, its ground at a slight angle. The follower is also specially ground to work with that angle and rotate.

When one or other is worn, and they cant rotate correctly, accellerated wear tends to occur.

I now realise that your not suggesting fitting new lifters, but some slightly less knackered ones for a short time, and in that situation, i'd say sure, go right ahead.

It is not the lobe ground under an angle, the lobe is not in the centre of the tappet hole.
If you remove all tappets and look through the casting holes you will see the camlobe out of centre.
Therefore the tappet will rotate a bit when the lobe passes.

Okay, so I'm bolting it back up now. The first torque stage is 20Nm, and I have a shiny new torque wrench which has that as its minimum setting. 20Nm just doesn't feel like a lot.

Is that definitely right? Just a bawhair over finger tight, then 90°, then 90° again?

Correct Gordon, 20Nm +90º +90º.
The first 20 is a bit tricky with such a large wrench, it's easy to rotate some 10 dgrees to much or too less. I have a small motorcycle wrench for the lower spectrum, it starts with 5Nm, maybe you could borrow one.
The final 90º I did not always give, mostly some 60 to 70º, scared as I am to break the bolt.
I'm not pretending that I can feel where the 'stretch' begins but after many heads in Classics and P38 I have a feeling 'enough is enough' and stop turning the bolt.
See to it the bolts are clean and have a drip of oil. And if you have one, use a 16mm impact socket, they stay better on the bolthead without wiggling off.
Reg. Tony

I bought two Draper 16mm impact sockets although I took the first head off with a normal 12-point socket. That's it bolted up, I don't know how critical the angles are but I eyeballed it with the markings on the socket and extension. The second 90° is pretty damn tight!

It's got two chances, I guess...

20 nm is more than little greater than finger tight. About 14 1/2 ft lb in proper money. Roughly the standard tightening torque for a half decent 8 mm bolt according to this : http://www.wtools.com.tw/STANDARD-BOLT-TIGHTENING-TORQUE.shtml. Interesting links but I defy anyone to make sense of the introductory blurb to the relation formulae between bolt and torque at the bottom.

I prefer the spring loaded handle with direct reading dial type like this https://www.cromwell.co.uk/shop/hand-tools/torque-wrenches/sw25-dial-indicating-torque-wrench/p/KEN5551250K for that sort of low torque work. Its very easy to feel whats going on. Important when pretensioning a stretch bolt. Theoretically not as positive as a click type but it takes only a modicum of care to hold better accuracy than the inherent scatter of a normal size click type. Folk tend not to know what they are so often found very cheap or even, like mine, free.

Clive.

Always feels like your gonna strip them, I always do the first 90 then let them sit for five minutes before I hit them with the second 90.
As Tony says, you can feel if it’s getting to tight, it’s ridiculous that the bolts are so tight, I’ve only ever stripped one, they take a lot of pressure.

Clive603 - depends on if you've got big fat bass player paws or not :-)

no10chris - I left mine a bit longer, about as long as it takes to get a beer from the fridge, remember I'm on call, and have a cup of tea instead.

I remember those days of being on call, I was 24/7 , used to drive me insane

We have so little that requires any more than a "send me an email, I'll fix it next working day", so it's not a biggie.

It starts!

Can't be bad. Driven it yet?

Okay, it won't rev particularly high on petrol, sounds like it's being starved of fuel. What obvious thing have I got wrong?