<VV> Spark Plug Gap

Smitty vairologist at cox.net
Sat Jun 21 13:29:11 EDT 2014


This is a generic question about spark plug gap size.
For a given motor, Corvair or otherwise, with everything in good working
order and a good ignition system, what is the impact of running a smaller vs
a larger gap size, say for arguments sake .030 vs. 035?
Smitty Says.  Bob you are going to make out better asking if anybody elses 
wife was prettier than yours when she was young.
I know there are lots of opinionated people out there who will argue with me 
just because I am me.
What matters most is lighting the fire.  I think automakers and plug 
manufacturers come to an agreement on what gap to use for a given product. 
That would be the point at which the fattest fire can be generated 
considering the wide range of conditions you mentioned.  I learned years ago 
that a set of new plugs at factory settings in a turbo would perform lousy 
in just a few short miles.  Often not able to even get boost in a couple 
thousand miles.  A CD ignition was a help but then I could often put the 
fire out under full boost acceleration.  I don't know if the spark wasn't 
able to penetrate the high pressure mixture, which I assumed is what was 
happening.  I tried increasing the gap and then lessening it to no effect. 
I tried to find the best hot rod coil system I could afford.  Then I found I 
could open the gap up and still keep the fires lit under high combustion 
pressure conditions.  Points were taking a beating carrying the amperage.  I 
chose to go that route and not convert to a points elimination system. 
Ignition points is not a dirty word to me.
If I were to go back 40 years I would take a GM HEI distributor and coil 
with me.  GM reliability and availability of the working parts.  More spark 
than you are likely to ever need.  Set the gaps at .045 and run them till 
the electrodes are worn away and still lighting the fire like everything is 

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