There's no simple answer because the question is complex. But as a
rule of thumb, you can increase gap 10-30 thou over stock.
The caviats are several.
First, the greater the gap, the hotter your coil will run and the
higher you'll charge the rest of the high tension side. This
burns out coils, promotes arc over in distributor caps and
perforates plug lines. Anything that was borderline before
you increase gap will fail quickly with the increased load.
Air is an insulator. The better your engine stuffs air
into itself, the less gap you can use. That's why blown
engines run gaps in the .20-30 range. That's with
hot coils and such.
The actuall optimal gap is determined with a dyno.
You probably don't want to get one. You can determine
optimal gap roughly by recording mileage and increasing
gap in incriments of about 5 thou and comparing. Add
in some acceleration comparisons as well. When you reach
the peak and start falling off, back off 5-10 thou and your
about right.
>>> Ron Deaver <rrdeaver@emagichappens.com> 10/23 2:29 AM >>>
The resurrection continues (I do plan on a writeup when not buried under
the bonnet). I would like to replace the stock 20-year old Lucas coil with
something not prince-blessed. The Bosch Blue Coil sounds good, but one
thing comes to mind...
Hotter coil ads often advise that you can run a larger plug gap when
upgrading to the hot coil. I have not found advise on just *how* much
bigger of a gap to use.
My lil brown 1980 Spitfire has Allison ignition and Bosch Platinum
plugs. Any advice on how big of a plug gap to use with the Bosch Blue
coil? Nope, I do not have a resistor installed (none that I can find anywhere).
|