123 Dizzy for 140 engine

Just wondering if anyone has any real, hands on experience fitting a 123 distributor to an XK 140 engine with a C type head. Looking for pros & cons before I pull the trigger here.

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Welcome to the best resource on these cars you’ll find on the planet! I know of people who have used 123 in many more modern Jaguars, and there isn’t all that much difference between them and the older 140.

Hi Fred, I’ve had a 123 distributor in my 140 for 5 years without a trace of a problem. It starts, runs and stops perfectly unlike when I mistakenly used Pertronix products. Never again will they darken my door.
The 123 is easy to fit but you may need to change your HT lead connections.
There are many, of course, who swear by traditional points set up and that’s fine also.

Hi Fred,

123 is really superb.

I do not race, but in respect of my (good) points system, I really find that from 4000 rpm the engine revs smoother.

The Bluetooth version gives you a very easy curve adjustment with a mobile phone.

So far roughly 2000km trouble free.

Many thanks,


The idea of using your phone and Bluetooth to make adjustments to your XK makes me shudder!

I have had a 123 Tune on my XK140MC for almost ten years and it is an amazing bit of engineering. I was able to “fingerprint” the advance profile for perfect timing and vacuum. The vacuum settings are very confusing although I think they have changed them in the newer model. A very good buy. Now if they could only do a job on the H6 carbies!

Yea… try it and you might feel differently…:wink: