Fwiw, regarding Autolite plug numbers:
Numbers with an odd beginning, ie: 75 are NON resistor.
Numbers with an even beginning, ie: 85 are resistor.
In this case both are 14mm short reach ( 3/8 inch ) plugs with the same heat
range. The heat range is the second digit...the 5. A hotter plug would be
a 76 or an 86, a colder plug would be a 74 or 84. You will probably NOT
find the colder plugs readily available on the parts shelf.
For the B and RB series Mopar engines the 85 is probably the most common
Autolite part number. If you had the need you will find the next hotter
plug the 86 is still very common. Non resistor plugs are becoming a thing
of the past but if one had occasion to need them you can still find them.
As an aside, and from recalling a recent thread, regarding Champion numbers:
R is for resistor
J is for the physical dimension of the plug ( 3/8 short reach )
12 is the basic heat range
C is for Copper
Y is extended tip as I recall.
Most of the big block engines in the imperials would use a RJ12C or RJ12YC
plug, the extended tip helps keep it from fouling. This is again probably
the most common plug for our applications, and then the RJ14 series for the
next heat range.
If you had a 318 / 360 series LA engine, you would want a 65 or 66 Autolite,
or a RN series Champion.
The sad part of this entire thing is that the part number keys are in the
back of the plug catalogs, presuming that the parts droid at the store
actually HAS a paper catalog at their disposal and someone actually either
took the time to teach them how to interpret the information or the
counterman actually took the time to browse the book.
Take care
Mikey
62 Crown Coupe
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