Another common problem with high energy coils is that people overlook
the relationship with the plug gap. On a high energy coil, you should
run a larger gap. If the gap is too small, the energy is also wasted.
Perhaps with a larger gap, the MSD would have produced a longer burn.
There are plugs that run gaps as large as .060". My car has an old
Mallory coil in it (inductive), but I found it really liked a gap of
about .030-.035 instead of the .020-.025 I would normally have used on
the same plugs. Increasing the gap reduced a problem I was having with
a mid-range stumble.
Gerald Brazil wrote:
>
> Zeke I had a similar problem when I switched to an MSD ignition. I had one
> of those hot Lucas competition coils The car ran fine until about 4K and
> then it just would misbehave and it was a real task to get it to 6K in the
> lower gears and it just went nowhere in top. I tried everything. Finally I
> took it to my tuning Guru. He put it on an Allen Smartscope and spotted the
> problem within 2 minutes.
>
> My spark voltage was about 80,000, but as rpm increased the duration was
> dropping and above 4k, it was so fast that it wasn't firing long enough to
> propagate a good flame. He got me an epoxy filled Niehoff coil (can't recall
> the #) the produced a much lower voltage than the Lucas. Now my final
> voltage was a lot lower, but I had a spark that lasted enough to get things
> burning. After that, the little bugger was pulling hard at 7500.
>
> I think that coil sold for less than $20. A nice cheap fix.
>
> Another case of where more isn't always better.
>
> GJB
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