Wednesday, 15 August 2012


By the end of this month that scary engine start up moment will be imminent with only the exhaust system, cooling and ignition left to fit.

In close to fifty years of driving old cars, I would say that nine out of ten problems I've encountered on the road have been electrical and often ignition related.  Back in the sixties, even brand new cars had problems, especially on cold wet mornings when they were reluctant to start.
With this in mind, I'm keen to ensure that my electrical and ignition installation will never give me cause for concern.  It would also be good to see a pristine 1950 engine bay.  This competing requirement will inevitably result in some compromises, but original HT leads and plug caps would be good.  The downside might be interference to my proposed DAB radio installation, electro magnetic interference upsetting my electronic ignition system or RF noise locking up my neighbour's digital TV's as I pass by.  I really don't know and can't find any one that does, so it will be a case of try it and see.  Fortunately I have access at work to a Spectrum Analyser which will display whatever nasty stuff is being radiated and provide precise data relating to the effect on digital radio and television signals.  I'll let you know the outcome.
Cap, conduit and HT leads not quite as original and needing
some attention
XK's for the first few years had the HT leads routed under the carburettors and around the back of the engine leaving the front uncluttered.  It was not until 1953 that they were routed over the cam cover, possibly for some technical reason or maybe just to save a few pence on a couple of yards of HT cable.  Again, no one seems to know.  As a very early 120 my car would have benefited from that original design and in the absence of any good reason to revert to the later layout I adopt the original route.  To minimise the possibility of cross firing between leads (one of several reasons mooted for the change) I run them in an aluminium tube with a central polypropylene rod and original Bakelite spacers to keep them separated.  The tube is heat insulated from the engine with a calcium silicate sheet.
Original HT lead conduit cleaned up beautifully with black
boot polish.  Note polyprop rod to keep leads separated.

Neat solution to route leads under carbs

Note red 'Champion' labels on plug caps.  Not sure if they should be there. 
Definitive answer for a December 1950 car anyone? 
To improve on the usual practise of simply relying on strands of wire pushed into retainers to make electrical connections, the HT lead copper conductor is carefully splayed within the brass connector to the distributor cap and soldered in place.

Centre copper conductors splayed and soldered to brass connector
Next consideration is the distributor.  I have over the years had many a disagreement with the Lucas unit in its various forms and as its not particularly prominent within the engine bay, it will have a modern replacement.  I fitted a 123 Ignition distributor to my Frogeye around three years back and have never touched it since.  The very latest version is the 123 Tune with a USB port to connect to a Lap Top and programme in whatever curves you want.

Superbly engineered 123 Ignition 'Tune' distributor with USB
 port to programme your choice of advance curves.

The software to run this is downloaded from : 

Running the programme, the first screen displays a very comprehensive dashboard with clocks for RPM / Crankshaft advance, Coil current, Distributor temperature, Vacuum and a timer to compare acceleration between two pre-set RPM points.

The second screen allows you to select seven points of crankshaft advance and seven points of vacuum advance / retard.  Each series once selected can be saved to file.  The distributor is connected via a USB lead and two 'curves' selected and downloaded into it.  It is possible to switch between them by applying 12V or 0v to the distributor's yellow lead.

The XK workshop manual has sufficient information to allow you to emulate the original setting for the Lucas distributor or you can put in your own.  You can even play about with them on the road, using the timer to compare acceleration between settings, but only after confirming that you are a passenger and not the driver, a neat touch.  If you happen to have access to a rolling road and dynanometer then you could really have some fun.
I had the benefit of following on from friend Tony Hamnett who fitted one to his 120 a while back and emailed me a whole series of curves taken mostly from the 123 Ignition website and tweaked for his particular application.  I simply selected the two he found best, imported them and downloaded them into the distributor.
My most likely application for the two settings, given the shortage of 99 Octane in this part of the County of Yorkshire (12th in the Olympics Medal table or top by a very long mile on a population / medal basis) would be to switch between curves optimised for high and low octane fuel.

Heat shrink nicely finishes of caps and will keep moisture out
On the recommendation of a couple of respected enthusiasts, I fitted a set of Iridium needle point plugs to my 140 about eighteen months / 7000 miles back and its run like a sewing machine ever since.  They are quite expensive at around a tenner each, but so far show no signs of wear so they're naturally included in the 120 spec.

Iridium needle point plugs - probably the best present an XK could have

From an appearance stand point, the end result is just about as good
 as I had hoped for
So that pretty well ties up the ignition system, all done with great care and attention, and I have absolutely no doubt that when I switch on the ignition and press the starter button for the first time - it won't start!

Autobodycraft, the company doing the 120 body, staged their own charity Motor Show on Sunday 12th August.  More than 100 vehicles were on display, 1500 people attended and over £5,000 was raised.

Great example of Yorkshire humour

Rat car with monster truck turbo diesel
Next Post beginning of September