[Spridgets] SU Needle Recommendation

[Dean Hedin]

Howard, You are not that far from stock.  The extra 20cc's are not a game
changer.
I think you will be fine and well within adjustment of the standard 1.25
SU's.
(AN needle and Blue spring). 

If you want to experiment.  A 1275 Cooper S would have had an M needle and
Red spring.
But I don't think that is what you want.

The above is from the spec tables of "Tuning SU Carbs"  

SU's have a wide latitude of main jet adjustment. Very forgiving.

You won't find the absolute perfect needle without unlimited time on a
rolling dyno 
and having a giant collection of needles to try.

>From that book, the author states "It's best to use the red spring, but if
the carburetters
are suspected of being on the large size for the engine then the blue spring
should be tried"

So from this statement alone we can imply that the 1 1/4" carbs are already
oversized
for the 1275 from the get go, since they come with a blue spring stock!

If after adjustment you find it weak on acceleration, then I would open the
man jet a little more
and maybe run thicker dash pot oil.  But I doubt this will be an issue.



-----Original Message-----
From: spridgets-bounces at autox.team.net
[mailto:spridgets-bounces at autox.team.net] On Behalf Of Howie
Sent: Sunday, April 21, 2013 6:36 PM
To: Gerard
Cc: spridgets at autox.team.net
Subject: [Spridgets] SU Needle Recommendation

I need to obtain recommendations on needles and springs for the following
recent engine build:

1275 bored to1293
1316 smog head, ported w/ slight polish
New valves, springs, unleaded seats
1.5 roller rockers
Pertronix Ignition
Twin 1.25 SU's
K&N filter housing
Spirited street driving

Any informed recommendations appreciated.

Howard Collins