Paging Muck

You're right about B12 valve clearances, they are screw and locknut.
I've never had to do them and someone must have lied to me when I asked
what they are.

 

Maybe they didn't actually know. Anyway, it's not that important, if you
do your own work, which I do.

 

what's the technical reason for bucket and shim over screw and locknut?

 

All sorts of things.

1. First, less reciprocating weight. The cam lobe operates directly on
the valve, with no need for a rocker in between. This means higher revs,
in theory.

2. Again in theory, capable of higher revs because you don't get the
rockers "floating" at high revs (unless you use a Desmo set-up).

3. Cheaper to make, because of (1).

4. It allows you to site the camshafts directly above the valves, rather
than to one side, thus making for a more compact engine.

5. Nice large "wiping" area on both cam lobe and shim surface gives both
an easier life. This can, admittedly, be achieved with a nice large cam
follower if you have conventional rocker gear, but see (1).

6. Quieter. No noise from rockers and tappets going up and down.

Probably some others as well, but that's all I can think of right now (a
pint of Speckled Hen and half a bottle of Chilean red inside me)

 

Thanks, interesting post, that.

 

I should point out, re-reading it, that (1) and (2) amount to more or
less the same thing.

 

<remembers Sunday morning start-up>

Oh yeah, that'll be it.
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| ___ Salad Dodger
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