[Healeys] Setting SU HD Carburettors

[BJ8 Healeys]

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



-----Original Message-----
From: healeys-bounces at autox.team.net [mailto:healeys-bounces at autox.team.net]
On Behalf Of Derek Job
Sent: Friday, August 17, 2012 12:50 PM
To: Forum
Subject: [Healeys] Setting SU HD Carburettors

I just obtained a copy of the SU Workshop Manual.

Flicking through the HD section I noticed the following

1. On single carb applications the idling speed is adjusted by using the
slow running valve.

2. On Multi carb applications  there is the following statement.

Item 1
Note: *Whenever the throttle adjusting screws are fitted they, and not the
slow running valves, must be used to adjust the idling speed*. Screw down
the slow-running valves (which must remain closed) and set the throttle
adjusting screws 1.5 turns open. In items 2 and 3 adjust the idling speed
with the throttle adjusting screws.

Item 2 says:

a) restart the engine and turn the slow-running valve *OR* the throttle
adjusting screw, an equal amount on each carburettor to give the desired
idling speed.

Item 3 says:

a) Turn the jet adjusting screw an equal amount on all carburettors, up to
weaken or down to enrich, until the fastest idling speed consistant with
even running is obtained

b) Re-adjust the slow running valves, if necessary.

Does anyone else out there find this contradictary. Are the slow running
valves to be used to adjust idling or not?

Any thoughts?

Derek