Zkx14,
Thank you for your email and information.
The slant 6 engjne used 2 types of plugs: gasket seat (early engines all displacements) and taper seat plugs (I believe mid 70 production).
Spark plug brands and types are extremely subjective.....like which beer is best or shoes are more comfortable or .... However, spark plugs are manufactured to strict SAE atandards (Society of Automotive Engineers) and engine manufacture's cylinder head design and emission requirements. Whether you have a taper seat or gasket seat cylinder head engine, it is IMPERATIVE THAT THE CORRECT TYPE OF PLUG BE USED. If you like Champion or Autolite or NGK brand plugs all well and good. The heat range of the brand is selected .... by trial and error or "seat of the pants" engineering or the DFL factor, its best to start out with a cold plug, as its easier to replace fouled plugs than melted pistons. Spark advance characteristics, mixture ratio and fuel distribution, cam shaft design, compression ratio are the factors in plug heat determination (at least the initial selection).
Do your own do dilligance. .... remember that your next door neighbor's brother- in-law's, cousin's sister's husband's friend's best "buddy" has no clue to what YOU need for your application.....CAVIET EMPTOR applies.
Bob Renton
