SU Nozzles variations

[nismou20]

I have a assortment of used nozzles and my 2000 idle is not clean as in the past (Rich). Is there any way these were designated from the factory? I see different numbers and colors on the plastic bases. I can go through trial and error to find one that works but just wondered. My present nozzles were cranked all way up to leanest positon and now wondering if I might have been running on nozzles not for U20. Car runs great just that I have to nurse it at idle some of the times.

[sevenmilebridge]

You can pull the needle down maybe 1/16 inch may help you at idle being too rich. With the idle nuts closed all the way something is worn.

[JT68]

For the U20, there are only 3 types of nozzles. Early front, Early rear and later 45 degree style. All are the
same .100 bore. What happens over the last 50 years, is a well meaning P.O. mis-aligns the jet and the needle rubs against
the perfect .100 jet bore. Then it becomes ovaled.

Once that happens they will never work properly until you replace the nozzle (and likely the needle too) and get the nozzle properly
centered.

It is just like worn out throttle shafts, SU carbs will not work consistently until that gets addressed. Shiny plating is irrelevant; if the throttle shafts are worn, or the nozzles or the needles are tired, SU’s will be inconsistent and frustrating.

[redroadster]

If you have the cleaner off and running I found the air flow from the fan messed up the fuel ratio ,could not get it right until I loosened the fan belt

[david premo]

The advice of loosening the fan belt is very bad advice. Here’s why, 1 the cooling system is going to be compromised by the water pump and fan causing the engine to run hotter. 2 the alternator will not put out the proper voltage, potentially under powering the ignition system causing incomplete combustion. If the air flow off the fan is truly causing this problem then all you need is a shield to keep the airflow away from your carburetor inlets and not risk overheating your engine. I’m sure there are more reasons not to loosen the fan belt, but those 2 are more than enough to keep from doing it.
Dave

[redroadster]

I found either works its only a minute or 2 so no problem on current or running hot , don't think I loosened it to enough to stop
But thanks for thinking about me
A substitute air cleaner that allowed access to the nossels might be the best solution

How do you get Reverse gear in a Auto Trans?
as the rotating assy turns one direction and doesn't have a inserted gear like a manual Trans

[nismou20]

As per Ztherapy there is no way to tell without a pin gauge. Rebuilders may use paint or markings. I had a small assortment and found one that works for now.