How to explain this without sounding like a know it all.
I own a stock car racing team in Pennsylvania. I have over 30 years of mechanical experience and I have been trained to work on all types of vehicles. I also do many hours of research both for myself and for my race team and we build all our race engines in house.
It has been found that all spark plugs basically work the same and no spark plug actually gives you more power. There is nothing to be gained by using one type of spark plug over another type. HOWEVER
Spark plugs works on the basic precept that they ignite the fuel charge in the cylinder. The hotter the spark the more complete the combustion.
Technically - when you put your spark plugs in the cylinders, with conventional spark plugs, the spark plugs should be indexed so that all the spark plugs grounds are in the same direction - since the grounds can shroud the spark momentarily. They actually make a threaded gauge for the old style spark plug where you can screw the spark plug into the gauge and check to see where the ground ends up.
The newer style spark plugs has multiple side electrodes and multiple edges on the center conductor which promotes a larger spark - due to the fact that the electricity travels over the outside of the conductor and the more surface area the center conductor has, the more spark it can make.
In previous times, this manufacturing technic was very expensive and cost prohibitive. = only used in racing and not in everyday vehicles.
All new spark plugs with this type of design - along with any spark plug with a irridium tip or platnum tip - cannot be gapped. Trying to gap these spark plugs usually damages the irridium or the platnum and ruins the spark plug. Not to mention the fact that you cannot get all the electrodes spaced to the same tolerences as when the factory manufactured the plug
In all cases, these spark plugs are gapped from the manufacturer and should be left the way they are, no matter gap the manufacturer calls for. when they misfire - you just throw them away and buy new ones.. Some engines - it takes hours just to change the spark plugs, and so you would not want to waste shop time, trying to clean and gap a set of plugs when a new set of plugs costs half as much as the shop time it costs to take them out and put them back in.
I have tested many different manufactures and styles of spark plugs in the 5.3L engine and some of the best performance I found was with a 6213 Bosch Platinum.
It is more important to establish a good ground between the threads of the spark plugs and the aluminum heads then to use the best spark plugs and have rust on the threads. It's also very important to remove the old spark plugs when the engine is cold. The factory plugs starts to fail - not perform as well as new plugs in as little as 50,000 miles on a 100,000 mile plug.
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