In a message dated 1/10/2006 4:27:32 AM Central Standard Time,
gasit@bellsouth.net writes:
<<I’ll bite! What modifications in 1/2 hour and where do I get this
information? This sounds better than changing carburettors.>>
OK, Assuming your carbs are in top shape with no throttle wiggle, etc., and
they are surgically clean.
Look down the throat of the carb and see what is causing air flow
restriction. Start with the fasteners that hold the throttle plate in place, they
protrude into the air space a little too much. Change them to the rounded button
head type that use an Allen Key. To really gain more airflow you can cut the
throttle shaft so the disc is secured on just one side, use Red Loctite in
addition to the aforementioned fasteners to hold the disc in place.
Using a Dremel or similar tool grind off all casting imperfections in the
interior of the carbs, look closely and you might see all sorts of things that
the Skinner Brothers didn’t want and Sir William was too cheap to pay someone
to remove. Die casting has improved a lot since the 50s.
Get a piece of glass and secure some 120 grit wet/dry emery paper to it and
rub the rear mounting flange in a figure 8 pattern to make sure it is
perfectly flat, de-burr the edges if necessary.
Make sure that the gasket between the carb and the isolator packing is not
obstructing the airflow, same with the gasket between the packing plate and
the manifold. I use a genuine asbestos packing plate. They are unobtainium now
because too many people either ate them or whatever and we need to be
protected from ourselves… IMHO it’s worth searching for them - if you can’t find
them the Bakelite ones are 99% as good, they’re just not as flexible that’s
all.
Clean the air cleaners according to the manual and re oil them using either
5W oil. Use the proper oil in the dashpot too.
or
If using an aftermarket air cleaner use a stub stack inside the air filter
housing - you can’t do this with the factory type but if you replace it with
an after market item like K&N (who have a great marketing dept. and a so-so
product) spend the extra few Dollars/Pounds/Euros, and get the stub stacks.
There is only one way to reinstall the discs, make sure you install yours
correctly and not upside down (or inside out). I have found a cheap 10X
magnifing glass to be useful.
Go with a lighter spring to increase response.
Soak all cork gaskets overnight in 5 or 10W oil before installation.
Do not over tighten the carbs as you will warp the mounting flange.
Use real SU parts when rebuilding, a lot of “rebuild” kits being sold are
junk. Use the real thing, more expensive but worth it. I’ve had good luck with
Burlen.
Smooth out the bridge with the Dremel, be gentle, don’t remove a lot of
metal.
Get the Genuine Factory SU Workshop Manual and follow it to the letter in
setting up each carb and then setting up the pair.
Get the Genuine Factory SU Workshop Manual and follow it to the letter in
setting up each carb and then setting up the pair.
Get the Genuine Factory SU Workshop Manual and follow it to the letter in
setting up each carb and then setting up the pair. I believe that there are
about 5 people in the entire universe that have driven any SU equipped car where
the carbs have been set up properly.
Some people have opened up the bore but that’s beyond the scope of this and
should only be done for SERIOUS racing.
I hope this helps, most of it is just common sense. Stare at the carbs for a
while (I REALLY need to get a life) and things will become clear.
Kind Regards,
Ron
670425