My 2¢...
Twin HS4 SUs are well proven in this application, provide good
performance and good response, and all parts are available. The setup and
maintenance are also well documented in the various manuals for the
earlier cars. If you buy new you won't have to deal with most of the
common problems involving wear.
Larger than stock SUs (HS6) are probably not very helpful on an
unmodified engine.
The Weber DGV downdraft is a common modification, but is not any more
potent performance-wise than twin SUs. They are pretty trouble-free once
set up properly, but you won't find any info about setting it up or
power- or emissions- tuning it in your MG manuals. The Weber manual won't
have any MG-specific info, either. You may gather that I am warning you
that you may be at the mercy of an "expert". But then again, it may work
fine just out of the box. My indirect experience is with a friend's
Sunbeam Alpine. The DGV fit right in, but he had to fabricate a throttle
linkage. It was perfectly reliable, but he was never able to tune it to
get rid of a "flat spot" in acceleration.
FWIW (I admit I'm predjudiced in favor of SUs -- they just look right).
David G.Butcher had this to say:
>Hi all.
>I'd like to replace my stock ZS carb to improve power, reliability, fuel
>economy and emissions (why not ask for everything?). My car is a daily
>driver and I need to pass our local air emission test when all is said and
>done.
>So far I've heard everything -- twin HS4's, twin HS6's, single Weber
>downdraft. I think the only consensus at this point is the dual Weber
>sidedraft conversion wil probably not allow me to pass emissions, so I've
>ruled that out.
>I don't have first hand experience with any of these configurations. Any
>insight, advice, comments will be very appreciated.
>Thanks,
>Dave
>1979 MGB
>
--
Max Heim
'66 MGB GHN3L76149
If you're near Mountain View, CA,
it's the red one with the silver bootlid.
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