Re: MSD 6A STATUS REPORT

[jlandry@domain.elided (John A. Landry)]

In Linda Tripp's secret telephone recording, Monica and Mike Bucher
<mbucher@domain.elided> were heard saying...

>New set of plugs @.060  restored the easy starting.  So, I now know that
>.080 is too wide, but what is the optimum gap to use with the MSD 6A?  Is
>.060 too wide?   It sure pulls better at .060 than at .080.  

Sparky,

As you probably know, the greater the gap, the greater the voltage is required
to build before a spark can bridge the gap.  A huge gap like .080" puts a
severely increased load on your secondary ignition system.  Remember that
electricity is always trying to take the path of least resistance, and with a
properly set up ignition system using quality components, the spark plug gap
is the path of least resistance.  Unfortunately, when you start increasing the
voltage to very high levels due to such a large plug gap, something else might
wind up being the path of least resistance... like the terminals inside the
distributor cap.  For various reasons, your hard starting could be the result
of the spark jumping to the wrong terminal or directly to ground inside the
cap.

The premature plug erosion is likely caused by the increased spark plug
temperature due to the high voltage spark (caused by the excessive gap).

The bottom line on the plug gap question (IMHO) is that you don't *need* such
a huge gap unless your engine is running some really hard to ignite fuel
mixture.  Try something reasonable like .050".  That will give you a plenty
hot spark to keep the plug clean, excellent air / fuel mixture ignition, but
not so hot as to cause premature electrode erosion.  Remember that the higher
the compression ratio or more turbulent the flow in the chamber, the more
voltage required to jump the plug gap.  If you have either or both of those
conditions, you want to keep the gap on the smaller side... like maybe not to
exceed .040".

>Maybe those triple electrode plugs may be on to something for the MSD
>ignitions, 3 time the plug life!!??  Or switch to platinum plugs?

If you simply must run such a huge plug gap for some reason, then you
definitely want double platinum spark plugs (both electrode and tip made or
coated with platinum).  I personally like standard Bosch Platinum plugs and
would never think of using regular plugs anymore.  Don't waste your money on
double, triple or whatever electrode plugs.  You money is better spent on more
frequent oil changes and flushing the cooling system annually!

Regards,

John L.
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