[Healeys] Setting SU HD Carburettors

[Bob Spidell]

re: "Does anyone else out there find this contradictary." 

Not after you've read the instructions about 37 times. (I think) it means that in Items# 2&3 disregard the instructions--probably written originally for single-carb applications--and use the throttle adjusting screws instead of the slow-run valves. 

My technique is to set a slightly slow idle with balanced airflow with the throttle adjusting screws with the slow-run valves closed, then open up the slow-runs equally to get the desired idle speed (and rebalance). This way, when I'm at high(er) altitude--my base tuning is near sea-level--I can open up the slow runs an equal amount; e.g. a half-turn, to bring the idle back up, then turn them back down when I get back down to SL. 

Also, I prefer for the 'throttle stops' to, well, stop the throttle plate than have it slam against the bore. 

Bob 


-------------------------------- 
Bob Spidell - San Jose, CA 

----- Original Message -----

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