A problem with the typical internal combustion engine is the fact that each engine is designed to receive a particular type of spark plug. That is, the spark plug port of the engine will be machined and threaded at the time the engine is manufactured so that a particular configuration of spark plug will threadably engage into the spark plug port. Since the spark plug is attached by threads at its base to the spark plug port of the engine the threads of the spark plug must exactly match the threads in the spark plug port. Threads of spark plugs vary significantly, and some are designed to Metric measurements, while others are designed to English measurements. Additionally, the pitch and spacing of the threading have to match. In order to attach a spark plug to an engine that does not have the same threading as the spark plug the port has to be resized and re-threaded, perhaps by some type of welding and machining process. However, this can be a costly proposition.
FIG. 9 illustrates a conventional spark plug 10 threadably inserted into a port 12 of a conventional cylinder head 14 for an internal combustion engine 16. Those ordinarily skilled in the pertinent arts will understand that the remainder of the engine is not illustrated. The port 12 includes a threaded section 12a, a step 12b providing a sealing surface, and a counter bore section 12c opening outwardly on the cylinder head 14. Similarly, the conventional spark plug 10 includes an electrode section 10a providing a spark gap 10b, a threaded section 10c leading first to a sealing shoulder 10d, and to an external metallic body section 10e, which provides wrenching flats 10f. Above the metallic body section 10e, the conventional spark plug 10 includes an insulator section 10g, which is usually formed of ceramic. Atop of the insulator 10g, the conventional spark plug 10 carries a metallic contact 10h, which provides for connection of electrical potential to the spark plug 10 in order to effect a spark across gap 10b. A gasket 18 is sealingly captured between the shoulder 10d and sealing surface 12b. Some conventional spark plugs employ a tapered sealing surface which sealingly engages directly against a tapered seat of a cylinder head without the use of a gasket.
In view of the above, it is easily appreciated that the cylinder head 14 is configured and adapted at the time it is manufactured to accept only one configuration of spark plug, and that this adaptation of the cylinder head 14 is not easily changed. Some who desire to modify a conventional engine cylinder head will remove the cylinder head from its engine and possibly machine the port 12 to accept a different configuration of spark plug. Also, those who desire to make other modifications to a cylinder head, or to add additional devices to it, such as a compression release valve will also remove the cylinder head from its engine and have machining operations performed to make these modifications or to add the additional devices. However, each of these modifications involves disassembly of the engine, as well as machining operations, and can be prohibitively expensive.
Thus, what is needed is a device for allowing a spark plug of differing configuration to be employed in an engine having a conventional spark plug port. Further, a device for allowing a compression release valve to be connected at the conventional spark plug port of an engine would be an advantage.