Just stumbled over this Needle Comparison chart / program written by Ian Hamilton, takes a little it of working out, but if you actually read the "Read me first" bit it helps ! Trust me I didn't read it all first and it took me having to read it to be able to use it properly.

You need to use F9 to refresh when you make changes twice to refresh the charts , but the charts do update on their own after a short while.

I am jetting some 2" carbs from a 4.2 E-type for a 3.8 fast road engine and you can compare needles across carb sizes and even from Stromberg to SU to compare needles.

It is hosted on Technical (Fuel Metering) so all the credit goes to Ian Hamilton for his efforts in compiling this.

Thought it may be of interest to others.

 

Argh! ~ it's going to take me a while to plow my way through that lot! I'm just reading "SU Carburettors Tuning Tips and Techniques." as we speak.

I'm a twin sidedraft Weber, Dellorto & fuel injection man.

Constant depression carburettors although apparently simple are a mystery to me. No experience with them.

Thanks ~ lots of learning to do. Bloody Skinner's Union.

I've only just learned that my car is supposed to be fitted with TL needles.

 

The program does have quite a lot in it if you want to tune the needles for optimum use, and you can compare a test configuration against a known needle and it will also give the nearest match to a standard needle (Neat)

Just read the SU high performance manual last night, just a little light bedtime reading.

A well tuned SU will give side drafts a run for their money, actually probably better if you take money into account !

A pair of 2" SU's, UM needles and ported head, chuck in a pair of .415" cams and your pretty good to go (provided the bottom end is sorted of course) !

Let's start a discussion on closed loop system conversions for the Mk2 and S-type ---- uproar will probably ensue !!!

I have considered installing Lambda sensors linked to an Arduino processor to monitor tuning, having built an RFID immobiliser for my MK2 which kills ignition and fuel pump for some security, and sets off the alarm if the RFID fob is not presented within a set time after the door is opened. I have extra inputs that I could use to monitor Lambda on each bank to give a guide to tuning or loss of it, but that's still in the thought process at the moment, but I will build in sensor tappings into the exhaust so I can play with the concept.

 

My sidedraft experience comes from owning, modding & tuning a long string of Alfa's in my youth.

Closed loop is a great idea. Just program an EPROM or whatever. I like ECU's. But I built my S Type to respect originality so I must stay with it & learn to tune & balance SU's. What amazes me is that I've made no effort to tune them. Not even used my Unisyn yet. I did a rough balance by even rev drop by pulling a plug lead on each bank & she runs & idles really well. Crank & flywheel fully balanced. Rods & pistons weight matched.