Adjusting Spark Plug Gap For Low And High Boost

Why Do You Gap Spark Plugs For Boost?

When a engine has forced induction, aka *(turbocharger,supercharger or blower) it increases the cylinder pressure and can cause the spark to blow out when the spark plug gap is too big. Too small of a spark plug gap can cause the engine to run rough and have inconsistent rpm's. It is important to know the least amount to gap the spark plugs as well as the greatest. Choosing the right spark plug is also very important. I run NGK Spark Plugs.

How Do I Gap A Spark Plug?

You gap a spark plug by using a special tool called a spark plug gap gauge tool. You can also use another tool called a feeler gauge. These tools allow you to slide a precision sized piece of metal in between the center electrode and the ground electrode of the spark plug to measures the gap space.

On the spark plug gap gauge tool it has a special hole seen in the pictures that opens the spark plug gap if it is too small. You can also open the spark plug gap with a feeler gauge as demonstrated in the pictures as well. As you lift up on the spark plug gap gauge tool it spaces the ground electrode away from the center electrode. To tighten up the gap you simply remove the gaping tool and tap the ground electrode onto a piece of wood/metal gently a few times and then recheck it with the spark plug gap gauge tool or feeler gauge until the desired gap is reached.

What If Spark Plug Gap Is Too Small Or Too Big?

Best Spark Plug Gap Performance For Low And High Boost Guide

For a low boost application *(under 15 psi) you will want to gap your spark plugs 0.028" - 0.032". For high boost applications *(15+ psi) you will want to gap your spark plugs 0.018" - 0.022". If you still experience break up under boost, the rule of thumb is decrease your spark plug gap by 0.005" increments at a time until the desired stable rpm gap is reached.

Still Getting Break Up Under Boost With Proper Spark Plug Gap

If you find yourself in this situation, then it's time to tune up the ignition system. This could be a COP kit (Coil On Plug), or simply replace the entire distributor, or ignition coil inside. Replacing spark plugs with new ones and changing spark plug wires should eliminate the problem. Always apply dielectric grease to the spark plugs top positive terminal. This will ensure the best conductiveness, and prevent corrosion. If you have a distributor, you also need to apply dielectric grease to the end of the spark plug wires that go into the distributor cap.