I know this has come up many times, but here we go again ...
NOS vs. Reproduction 24V plugs - any real differences? (I left out the T/O category - I already have a set of those in my truck )
Vendors (like VPW) list "plugs" - are these assumed to be the "medium" (not hot or cold) plugs? What's the practical difference in performance & efficiency?
You can trust your mother, but you can't trust your ground.
I'm no expert on spark plugs, but I wouldn't think there's such a thing as a 12-volt plug or a 24-volt plug. Either way, they allow a charge of several thousand volts to jump the gap! The main differences between plugs is their operating heat range (cold, medium, hot) and whether or not they're waterproof. You want the waterproof ones for a stock engine. NOS/reproduction doesn't really matter. The heat range is best determined by trial and error based on the type of driving you do and the overall condition of your engine, and you could end up with a misture of heat ranges depending upon the condition of the individual cylinders. Keep in mind that even the best T-245 engine is not even close to what you might call "high performance."
There is only one heat range of plug spec'ed for the stock setup, its the one all the vendors sell. (I dont recall the actuall part #)The military waterproof plugs are made by autolite and champion, the main diff is that the champions are cad plated and stay shiny brite and the autolite are black and will rust in a short time. If you wanted to change the heat range you could get a hotter plug from the parts store but theses plugs are sold at the stores only in packs of 10 for some reason. Lifer is correct plugs are not voltage specific, neither are the points/condensor. In the beginning 6v became the standard operating voltage for all cars and trucks, later when 12v (and 24) came along engineers and parts makers didnt want a line of similar parts in the different operating voltages. So came the ballast resistor which allowed the supply voltage to the coil to be dropped to the orignal 6v. allowing the continued use of parts already made. As well as ballast resistors some vehicles used resistor wire to the coil, or a coil w/ the resistor built inside.
I don't have my parts book handy but there are several spark plugs that can be used, they range fron cold to very hot, the suppliers generally stock the "normal" heat range plugs, IIRC the number is Autolite 4446, The voltage of the system 12 vs 24 volt doesnt mean anything to the spark plugs, it does to the coil and condenser. What does matter if they are the sealed (military) plugs or not, BTW I can special order the sealed plugs at my local auto parts store, assuming I don't get the young kid behind the counter!
I have a page on my website that features spark plug info for M37's and other Mv's (and some info that is applicable to civilian plugs as well) that was put together for us by PeteR down in Florida.
I picked up a set Autolite 2243 plugs at my local O'reily near my office for less than $7 each, and they had them in stock. BTW it helps if your parts store is in the same building as their regional distribution center. FWIW I beleive the condenser doesn't care about voltage either. Also I was told the resistor going to the coil is to make the points last longer. Many older vehicles would run a wire from the starter solenoid to the coil bypassing the resistor for a hotter spark at start up.
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