I have seen AC Spark Plugs that are marked #43N and others marked as #44N. It appears that they are "extended reach" AC spark plugs. Is that what the Letter N stands for...extended reach? Any idea if these AC spark plugs are correct for any of our Chevrolets?

Dave

The N spark plus were used in 348 engiines and if I emember correcly the 6 cylinder 7 main bearing engines (and Chevy II 4 cylinder.) 43N for trucks and high performance cars and 44N for cars.

Th e 348 used the 44N for normal service and the hotter 45N for low speeds and the 6 cyl came with a 46N

As any spark plug the heat range depended on driving conditions.

The "N" suffix indicates a reach (length of plug from seat to electrode) of 3/4". It is only half threaded. The same length plug that is fully threaded is an "XL" which is mainly used in aluminum heads. The standard length of an AC plug with no suffix is 3/8". Hope this helps.
Jeff

Thanks for the information on "N" spark plugs. I always wondered what models/years that these #44 AC spark plugs fit.

dtm

The 44N was used on hydraulic lifter 348 engines. The 43N was used on the high performacce solid lifter 348 engines.