Having purchased a 123 ignition system for my 1961 Mk2 3.4 I found instalation of the unit to be a relatively srtaightforward procedure. However ,I did have dificuilty trying to determine the correct advance curve for the unit relative to the engine. Recommendations seem to vary from no 2 setting from Jaglovers to no 7 from SNG Barratt! I eventually settled on the no 7 setting but feel that the engine is not as responsive as I would expect. (a bit flat) At the time of installation a new Lucas sport coil, silicon leads and complete set of plugs were also added. Timing has been set using a very good Snap-on timing light at 7deg. BTDC, the engine runs very smoothly on tickover around 700/800rpm hot and the car runs very well with no signs of pinking under load. My question is twofold, 1. Have I set everything up properly i.e. advance curve & strobe timing? and 2. Are my expectations to high for a 50yr old car? By the way the car returned 26m.p.g. on a 2000ml. round trip to the south of France earlier this year sometimes reaching speeds in excess of 90m.p.h. (according to sat-nav).Any comments would be greatly appreciated. Thankyou in anticipation of your reply, Colin.
Settings for 123 ignition
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Hi Guys , Further to my initial posting on the subject of curve settings for my 123 ignition , I have found a usefull forum on this very subject. On this forum is some very useful info from a chap called Rod re. settings for various Jaguar cars. To save you the trouble these are as follows for Mk2 engines. For 3.4&3.8 engines with 8:1 comp. ratio ,Curve B using 95/97 octane fuel. For 3.4/3.8 engines with 9:1 comp. ,Curve E with 97 octane fuel preferred. Apparently these settings should extract maximum efficiency and best fuel economy .For those of you who would like to see a detailed explanation of how these settings are arrived at try Googling 123 ignition forum! Sorry for you 2.4 owners out there as there does not seem to be any info on this particular engine. Hope this solves a lot of mistique which comes with this product. Colin.
Hi Guys, Further to my previous posting I have just got round to changing the settings on my 123 ign set-up. There is now a marked improvement in engine response &acceleration, (settings as per my previous posting) I have also started using super unleaded which may be a contibutary factor in the overall improvement of the engine performance. Suffice to say "HAPPY BUNNY" 
Hi Simon/Colin
The curves for the 123 unit can be found at www.tdcperformance.ca/tuning_guide.htm. Recent email from Ken Jenkins when I enquired about tuning my 2.4L suggests that static timing is unimportant (within the range 10-15 deg BTDC), but XK engines like around 24 deg advance at 2000 rpm and around 3200 at 3000 rpm (checked with the vacuum disconnected), with probably a max of 38 deg at 4500. Des Hammill's book on XK tuning suggests advance should be all in by around 3200 rpm, but this seems a tad aggressive. Curve F would appear to be nearest to Ken's suggestion with the static timing at the manufacturer's suggested 10 deg BTDC, but curve B is close with the static timing at 12 deg BTDC. Find a rolling road if you really want to get the best out of your system though.
I'm running a stock 22D6 distributor with a Pertronix Ignitor contactless system. The car also has SU carbs instead of the old Solex, adjusted for around 5% CO with TL needles. With the ignition timed to 24 deg BTDC at 2000 rpm the static timing is 12 deg BTDC. The engine is much more interested with the new timing than it was before. Hope this helps.
Best wishes, David
The curves for the 123 unit can be found at www.tdcperformance.ca/tuning_guide.htm. Recent email from Ken Jenkins when I enquired about tuning my 2.4L suggests that static timing is unimportant (within the range 10-15 deg BTDC), but XK engines like around 24 deg advance at 2000 rpm and around 3200 at 3000 rpm (checked with the vacuum disconnected), with probably a max of 38 deg at 4500. Des Hammill's book on XK tuning suggests advance should be all in by around 3200 rpm, but this seems a tad aggressive. Curve F would appear to be nearest to Ken's suggestion with the static timing at the manufacturer's suggested 10 deg BTDC, but curve B is close with the static timing at 12 deg BTDC. Find a rolling road if you really want to get the best out of your system though.
I'm running a stock 22D6 distributor with a Pertronix Ignitor contactless system. The car also has SU carbs instead of the old Solex, adjusted for around 5% CO with TL needles. With the ignition timed to 24 deg BTDC at 2000 rpm the static timing is 12 deg BTDC. The engine is much more interested with the new timing than it was before. Hope this helps.
Best wishes, David
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