Thread: Idle & RPM
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  #9   IP: 97.93.70.7
Old 05-08-2019, 10:58 AM
Dave Neptune Dave Neptune is offline
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Lightbulb Extra gap clarity

The additional gap will raise only the temp of the tip's as there will be a bit better fire (burn) at low idle speeds. It takes a bit more energy to jump the gap and that additional energy is what helps.

With a std ignition .035 is very doable as the RPM's and combustion pressures are not high enough to bother the plugs firing at higher RPM's that an A-4 will never see.

With an EI I feel safe running the gap all the way to .040" and did so on my boat for over 30 years with stock plugs and poor compression!!!

You will also hear that a tighter gap will increase horse power. This is only true with older "std ignitions" and a hi-performance engine. These engines develop enough pressure that makes it harder for the spark to jump the gap and a bit tighter would allow the spark to jump and all was well except that idle quality would be affected. Now with the super hot ignitions on everything we see gaps of over .070" and plug life of a hundred thousand miles or a whole lot of hours.

In my view an EI is a must as it is far more reliable and simpler to diagnose than points and condenser. Also with an EI your dwell will be fixed unlike with points. And old distributors are no good for setting the points by gap as the cam they run on is worn. This is why you see so often on this site the question "what is the dwell?".

Dave Neptune
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