[Healeys] Setting SU HD Carburettors

[Derek Job]

Steve,

It seems that not all HD8 carburettors are not the same. For instance the
ones installed on some Aston Martins did not have the slow run valve but
did have the throttle adjusting screws. My HD8 carbs have throttle
adjusting screws (not to be confused with the fast idle screws, which I
also have). The instructions I quoted from are in the SU Workshop Manual in
the section for HD carbs so it seems throttle screws must have been
installed on some of them).

Has anyone else out there seen any HD8s with the throttle screws. (ie with
4 adjusting screws in total). Until I see a few others its possible that
someone added them on mine at a later date. As they are there I am
following the instructions and closing the slow run valves and using the
throttle screws for adjustment.

Derek

On Sat, Aug 18, 2012 at 4:04 AM, John Sims <ahbn6 at verizon.net> wrote:

> You can find Steve Byers instructions for HD8 adjusting on the Technical
> page, Fuel System section of my site.
>
> John Sims, BN6
> Aberdeen, NJ
> www.healey6.com
>
>
> -----Original Message-----
> From: healeys-bounces at autox.team.net [mailto:
> healeys-bounces at autox.team.net]
> On Behalf Of BJ8 Healeys
> Sent: Friday, August 17, 2012 10:07 PM
> To: 'Forum'
> Subject: Re: [Healeys] Setting SU HD Carburettors
>
> Derek, the confusing and contradictory instructions that use multiple names
> for the same adjustment part is the main reason I decided to write my own
> instructions for adjusting HD8 carbs.  The SU manual tells you how to
> adjust
> a single HD carburetor, but for a multiple carb installation it refers you
> to another section where the "throttle adjusting screws" are mentioned and
> shown, but these (as shown) are not present on an HD8 carburetor.
> I based my instructions on the SU manual and BMC workshop manual, but tried
> to use consistent nomenclature and illustrate the process with photographs.
> These have served me very well, and I have shared them with others who have
> reported they worked for them, too.
>
> The last time this subject came up on the list, it was suggested that
> rather
> than setting the final fast idle speed with the throttle screws, as my
> instructions have it, the idle should depend only on the slow idle
> adjustment with the throttle screws being used only to set the choke
> operation.  I considered this, but decided to stay with the idle mixtures
> and carb balancing being set with only the "slow run valves", then
> increasing the normal idle speed to 1000 RPM with the throttle screws.  As
> they say, "it works for me" (and others).
>
> Steve Byers
> HBJ8L/36666
> BJ8 Registry
> Havelock, NC  USA
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