<VV> Spark plug gaps

[Tony Underwood]

At 02:19 PM 9/19/2007, FrankCB at aol.com wrote:
>
>Tony,
>     I certainly agree with what you recommend assuming  it's for a STOCK
>ignition system.  However, I SUSPECT (but I'm not sure)  that a 
>GREATER gap would
>be better for engine operation IF the system were  changed to an electronic
>ignition that can supply much higher voltage to the  plugs.  I seem 
>to remember
>that modern electronic systems in modern cars  use a significantly 
>GREATER gap
>(like 0.060 inch).

Yep, needed to light the lean mixture charge so as to keep misfires 
to a minimum.   Wide gaps require a hotter spark to bridge them.


>When I  changed the plugs in my 1966 Monza (with
>electronic ignition) many years ago  after high mileage the gap had 
>increased so much
>that none of my gap  measuring tools could measure it.  The center electrodes
>were worn  (eroded?) down to level with the ceramic insulation surrounding
>them.  And  the engine was STILL firing just fine - I was doing it for
>"preventive  maintenance"


As long as there's adequate spark to fire the plug, it will do its 
job... :)    My old first-car '61 Valiant Signet was firing on all 6 
nicely when I finally got around to replacing the plugs (never done 
it before) and found several that had the ground electrode eroded to 
the point that the plug had ~ 1/4" gap.   The engine never 
misfired.  Of course I hadn't run it that hard either...    Now, if 
I'd run it WFO up a mile long hill, it may well have sputtered and 
misbehaved bigtime but standard cruising without loading the engine 
never required more spark than the ignition was able to provide.   No 
misfires.   Cylinder pressures higher than normal require a hotter 
spark to jump the gap, all else being the same.   That hotter 
ignition and wider plug gap makes for a longer arc between the 
electrodes which has a better shot at lighting a marginal fuel-air mixture.


>     But does anybody have any EVIDENCE either agreeing  or DISagreeing with
>my suspicion that our engines would work better with a  greater gap?
>     Frank "questioningly" Burkhard


Your reasoning is on the money.

Heat up the ignition with a snappy coil fired by efficient 
electronics, run .05 plug gaps and it's unlikely that the engine will 
ever misfire if the carbs are anywhere close to being right.   It's 
gonna start easier too, as well as allow leaner mixtures to improve 
fuel economy if the heating issues don't get in the way.

Hell, if you don't leadfoot the engine and lug it around, the stock 
Corvair ignition will probably fire .05 gaps with no problems.



tony..