John Bourke wrote:
>
I emailed a UK owner with good 'B' series knowledge, over these shims,
and though his reply was good, it follows this. He agrees with many on
the List.
>
> >Dear John,
> >
> >Please excuse the intrusion, but these shims have me bugged....
> >
> >Your explanation for them is excellent, but why in none of the manuals
> >is no explanation given. I know of many people, myself included, who has
> >simply thrown them away. I have trawled many books to find anything
> >official from BMC/BL/Austin Rover, but nothing. I even went through
> >Practical Classic magazines from 1982!!!!
> >
> >As one reply says, the Marina and the Haynes manual says to retro-fit
> >them to earlier engines. Any ideas will be welcome.
> >
> >Neil.
> >
>
> Neil,
> I can't remember whether I saw this any where but then I have had
> my B since 1984 and have spent ages reading all sorts of things about
> building and tuning the B series engine-I did build quite a hot 1950cc unit
> which embodied all my ideas up till then in 1989 but finally realized that I
> could resist a v8 no longer and I have spent the last 3 years building and
> developing my V8.
> There are numerous examples of these little shims all over the B
> when you think about it.I am an architect by profession and I always try to
> understand my subject from first principles-aided by examining worn
> parts,symptoms etcI have seen examples of wear on old rocker shafts in the
> areas supported by the rocker posts-when you think about it-if you manage to
> bolt down the posts true to the axis of the shaft-without the tapered grub
> screw it would be free to rotate within the clearance of the rocker shaft
> bores.The clamping force of the tapered grub screw with it's tang drive was
> obviously found to be inadequate by the factory-possibly during the update
> carried out to the engine with the launch of the Marina.The shims under the
> centre posts create a slight misalignment which is enough to bind the shaft
> solid with no movement in the bores of the rocker posts and the slight
> upward bend of the shaft does not effect the geometry to any important
> effect.Consider this-every single piece of metal in the engine costs real
> money to make and is there for a reason-the shims may only cost a few pence
> but added up over say 200,000 units represents a real cost-they must have
> thought that it was worth it!
> I suppose I can just see why the enginners used the solution of shims
> intuitively and I don't need to have this confirmed by manuals etc. If you
> think about it how else could you clamp the shaft as a cheap retro fit to an
> engine already in mass production?
> You could bring out a new rocker post with a split in one side so that
> the rocker post studs could positively clamp the shaft at each post-but this
> introduces a weakness in the post and the material spec might have to
> increased with extra cost implications.
>
> I hope that this helps
>
> Regards John Bourke
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