Running cars with both I prefer the HS4s. The HIFs have the main jet and
float valve 'upside down' in the base of the carb and consequently the
access plate is 'under water' - I have had seals fail and leak onto exhaust.
The choke consists of another jet that is buried even further in the body of
the carb, and being a jet can block. They also came with those dreadful
poppet valves that stick open and interfere with flow. On the plus side
they are supposed to give better mileage/lower emissions and adjustments are
logically easier - you screw the mixture screw clockwise to get more petrol
in the mixture just the same as you screw the idle screw clockwise to get
more rpms, a bit easier than trying to explain to a newbie which way to turn
the HSs nuts.
My two-penn'orth.
PaulH.
----- Original Message -----
From: Bill Saidel <saidel@crab.rutgers.edu>
To: Max Heim <mvheim@studiolimage.com>
Cc: <mgs@autox.team.net>
Sent: Wednesday, May 31, 2000 9:09 PM
Subject: Re: Choosing a carb for a '79B
> For 2 more cents, how about a comment about HS4's compared with HIF's?
> Bill
>
> At 11:48 AM 05/31/2000 -0700, you wrote:
> >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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