Chris Hunt Cooke has had a difficult experience
with a new electronic ignition installation on his MGBV8 Roadster and says "I
would like to pass on a valuable (and indeed expensive!) lesson I have learned
about electronic ignition systems using a magnetic rather than optical system.
This is the importance of not having an excessive air gap between the magnetic
ring and the sensor. This eventually proved to be the cause of my V8 engine being
reluctant to run on all eight cylinders, and closing the gap cured the problem.
Measuring the gap has to be done using something other than a steel feeler gauge,
but plastic feeler gauges are in fact available."
Howlett adds "I agree Chris that the air gap is critical. My 3.9 Range
Rover engine has the electronic version of the Lucas distributor and, like you,
I found that the gap needs to be as small as possible without any risk of contact.
I must confess I didn't use any sort of gauge. I just put it as close as I could
In a similar vein, I have an electronic speedo on both my V8
and my Midget. On the Midget it is driven by a Hall effect sensor that "counts"
the prop shaft bolts on the differential flange. Speedy Cables say a 2mm gap is
satisfactory, but my speedo would lose signal at that distance and I had to move
it much closer."