The explosive power of the GMC spark plug has to be unleashed for your truck to perform its duties. This is the end component of the ignition system that brings your GMC engine to life. In the past, the GMC spark plug received voltage from the wire that was connected to the distributor. Inside the older distributors were points that initiated the spark. Today an onboard computer creates the spark that is then sent to the plug. No matter how old your GMC truck is, the specifications of your spark plug will have to be specific to its application. The depth at which the plug sits in the combustion chamber must be accurate, the spark that is generated also has to be in the correct heat range, and the gap of the spark plug's electrode must be set correctly. If any of these factors are off, it could damage your engine or cause it not to function. If the spark plug is not long enough to be in the combustion chamber, the air/fuel mixture will not be completely ignited. If the plug is too long, it could hit the top of the piston and cause a hole to develop in it. If the heat generated by the spark plug on your GMC truck is too hot, it could burn a hole in the top of the piston which will then have to be replaced. All of these factors are specific reasons why the correct plug must be placed in your truck's engine. If you break one during a tune up, go to the auto parts store and get a replacement. Just using any plug is not advisable because of the severe damage it can cause to your engine.