123 Distributor 4.2 Etype S1.5

[NickQe]

I have recently fitted a 123 distributor. I have currently set the advance curve on the lowest setting No 4. I am getting no pinking and intend to explore other advance curves. Has anyone else used this distributor and what advance curve did you use?

[colin6377]

Hi ,If you Google 123ignition forum there are some useful posts from a chap called Rod! He recommends for 4.2 Jaguar engines with 8:1 compression curve 9 using 95 octane fuel or curve A for 97 octane. For 9:1 compression select curveA using 97 octane preferred.Hope this is of help to yourself and others with similar problems. Colin.

[TonyB]

It depends on the compression ratio and the fuel you intend to use. There are also two different 123 systems for the Jag. I am using the JAG-6-R-V which has curves which gets the full advance going much earlier as recommended for modified engines in Des Hammill's book 'How to Power Tune XK engines'. This works very well on my 4.2 as long as I use Optimax or similar.
The only way is to experiment, either with a stopwatch, an accelerometer or a rolling road.