How can something so small be so important?
Of course, I’m talking about the spark plug gap, a critical factor in engine performance.
For an engine to perform efficiently, the spark must occur at the right time to properly ignite the air/fuel mixture in the cylinder.
Too small of a gap can lead to a weak spark and incomplete combustion, and too large a gap can lead to misfires, especially at high rpm.
With too big a gap, turbulence in the combustion chamber can blow out the spark. Typically, if you raise the engine compression or install a forced induction system, you will need to reduce the gap to prevent this from happening.
However, a larger gap requires higher voltage, which can be a performance benefit on some engines and is often a method utilized by engine tuners. But it usually requires a high-performance ignition system that can provide the higher voltage and additional energy to maintain the spark.
The spark plug gap is so pivotal to performance, that even a few thousandths of an inch can make a difference, and a misadjusted gap can also cause poor fuel economy and shorten the life of the plugs.
In addition to the gap, the condition of the center and ground electrodes is just as important. When they are new, they have very precisely formed edges which are designed to enhance the spark. As they wear and become rounded off, even if the gap is adjusted, the initial location of the spark will begin to change and potentially cause ignition issues.
Since severely worn spark plugs require higher voltage, it places additional demands on the ignition coils and can shorten their lifespan as well.
When replacing spark plugs, always check the manufacturer specification and make sure the gap on the new spark plug is properly adjusted, and even though most precious metal plugs come with a pre-adjusted gap, it is usually for the most common applications, but may not be correct for your specific application.
Don’t forget to use a wire-style feeler gauge when checking the gap on precious metal plugs, and only adjust the gap by gently bending the ground electrode so you don’t damage the precious metal tip.
Thanks for watching.
This video is sponsored by Autolite.