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MG MGB Technical - spark plug gap for sports coil?

can anyone tell me what the spark plg gap should be widened to for a lucas sports coil? i know you should open them a little but to what reading?
martin

.028 to .032 inches (.7 to .8 mm).

Mike!
mike!

Martin. I have tried between .035" and .045" without seeing any performance difference. Widening the gap from .025" to .035" did show a performance difference and the engine runs more smoothly with the wider gap. I settled on a .035" gap because this is the standard gap for US cars of that period and the later MGBs (thus easy to remember) and the fact that most gap gauges have a .035" gauge. Les
Les Bengtson

I gap the plugs on my MGC at .035....I've found a slight increase in performance, better fuel economy as well.

FWIW

rick
rick ingram

.035...hey, try a MSD6 box and increase the gap to .04 to .05

rn
RN Lipow

Like many things automotive, I don't know why, I just do as I'm told. From a John Twist seminar, my notes say "all--.035. HTH
Paul Hanley

The previous owner had installed a Crane Electronic Ignition & Lucas Sports coil, but kept the plug gap @ .25 thou. One of the first things I did when I bought the car 3 years ago was to increase to .35, and changed to a set of K&N air filters at the same time. Saw an increase in performance, but never was absolutely certain if it was the larger gap or better air filter. Probably a little of both.
Joe

The factory changed the plug gap from 25 to 35 in about 1976. All that does is increase the peak HT voltage in the HT system, and by that time the distributor (45D) and leads being used were probably better able to stand the increase than the earliest components. You don't get any extra energy in the spark gap unless you fit high-voltage electronic ignition, or a Sport coil, which isn't what was fitted to North American spec cars. Both the increased spark gap and high-voltage ignition can make the difference between starting and not starting under very adverse conditions like poor maintenance (which was why pointless ignition was required for the American market), but in a properly maintained car it makes very little difference. A sport coil draws additional current and puts additional load on the points. Another isue is whether you have a chrome bumper car with a 12v coil, or a rubber bumper car with a 6v coil and loom ballast. I've only heard of 12v sport coils but 6v ones may be available. Using the wrong coil will either result in *lower* spark energy, or rapid burning of the points.
Paul Hunt

This thread was discussed between 27/07/2004 and 30/07/2004

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