Chris Pappathopoulos <ctpappathopo@students.wisc.edu> wrote:
> Somebody is selling dual SUs and he thinks they are HS4s but he is not
> sure. How can I have him check to make sure of what they are?
>
Chris,
There are two easy ways to check:-
HS4's are 1 1/2 SU's which mean that the internal diameter of the
throttle body is 1 1/2 inches where it is bolted to the inlet
manifold, compared to HS2's that are only 1 1/4 inch diameter, and
HS6's are 1 3/4 inch diameter.
HS4's are bolted to the inlet manifold by two studs that are offset at
45 degrees to the vertical when looking at the inlet manifold side, ie
they use the two corner studs of a square stud arrangement around the
mounting flange. HS2's also use two but they are vertically aligned on
the manifold mounting flange, and HS6's use four studs. Thus, it is
possible to put HS6's (1 3/4 dia) onto a manifold designed for HS4's
(1 1/2 dia)as the mounting holes will line up, but not HS4's onto a
manifold designed for HS2's.
There are a few exceptions to this with very early SU's of the 1950's.
Hope that this helps.
==
Phil Johnson
66 Spitfire4 Mk2 FC73949
68 GT6 Mk1 KC13299
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