Ross MacPherson wrote:
> O! Most excellent denizens of yon list!
>
> How much is too much float /wear in the throttle shaft bushes in the
> SU
> body? I bought new shafts and a set of bushings just because I
> figured
> they'd need them. The carbs are original, 50 years old in Sept.
> They've
> got to be worn right?
>
> I dry fit the new bushings over the new shafts and they don't feel
> much
> different from what's in there. The aft carb has to have its shaft
> replaced
> anyway because the slow running adjust arm has worn a LARGE groove
> in the
> shaft inside it and the bore of the arm is now oblong. I'm going to
> make a
> bushing for the slow running arm and bore it to fit the new shaft.
> This is
> within my ability because fit isn't critical. But line boring for
> the the
> throttle shafts is pretty scary to me. Can they be bored out with
> an
> adjustable reamer? Anyone ever done this? If I have to go this
> route I'll
> probably take it to a specialist.
>
> As an aside, these carbs are so old they don't have
> dampers......really!
> Very early TC vintage.
>
> Cheers & TIA!
> ___ \______ Ross MacPherson
> / __ \ __ / /------|) arm@unix.infoserve.net
> / (___)---------/ (___) Vancouver, BC, Canada
> 1947 MG-TC 3528 1966 MGB-GT
Ross:
Line boring the bodies of S.U. carbs is not a very difficult thing to
do with the right tool. I use a fixed reamer 10thou. oversize and I fit
the appropriate shafts supplied by Moss Motors. I have had experience
of carbs. rebuilt by a company (who advertises in Hemmings) jamming in
the open position after some time running at wide throttle positions
when the heat under the bonnet caused the shafts to expand in the bores.
This can be somewhat inconvenient especially attempting to slow down
when situations involving high pucker factors suddenly occur.
It appears that although, for good throttle control, (especially at the
tick over mode of about 700-800 r.p.m.), the minutest clearance would be
optimum, in practice, a clearance between the shafts and the bore of
about 3thou. to allow for expansion is desireable.
Geoff Love.
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