This question popped into my head as I was falling asleep last night.

What difference does the size of the gap in spark plugs make in regards to hp and fuel mileage?

 

None as long as there is enough power behind the spark to jump the gap and ignite the fuel and air mixture. Most electronic systems will jump a gap of .100" whereas a point system will usually only handle .050". The wider gaps require more power which also causes faster wear of the plug tip unless you run high dollar hardened tip plugs.

 

Cool thanks

 

Well I dont totally agree with that.....A stock spark is usually about 25 to 30,000 volts..and jumps a .032" to .038" gap....for stock use or mild performane.. An HEI system is around 40,000 volts and generally jumps a .045" gap...Hotter spark longer jump (longer flame) Better Cylinder burn...

A Hi Performance Igignition... 50 to 60,000 volts will Jump a .050 to .060" gap (a longer yet Flame) Hence better cold starting..better combustion...cleaner combustion.. Hence a better running motor... a little Hp to be made..but not really enough to count on.. Just a better running engine...And in HP motors with High CR..you dont have to worry about spark blow out..with the good HEI Ignition...

Russ

 

Your numbers are what are concidered normal operating conditions. My numbers are concidered extreme. If you test spark per a manual you will find that points normally require the spark to jump as much as .25"(1/4") in the air. Under compression the distance is decreased because of a denser atmosphere. The really hot systems will require a spark to jump 7/16" during testing(usually the 60 to 80,000 volts systems) in any case none of the ignition systems use the full voltage potential during normal operation. A points system usually uses 15,000 to 17,000 volts of the 25,000 to 30,000 volts so there is some back up for failing parts and wear. But just like I said the wider the gap, the faster the wear on where the spark occurs, the plug tip.

"Hotter spark longer jump (longer flame) Better Cylinder burn..."

This statment is unture. You only need enough spark to ignite the mixture, any more is wasted and the only reason the manufactures went with hot spark systems is to compensate of the leaner mixtures to meet EPA requirements. The leaner the mixture the harder it is to ignite, so hotter spark required. Get rid of EPA and we would still prbably be using point systems (cheaper).