Got a box fully of RN9Y plugs at a local mopar sellout auction. I can't seem to find the cross reference of what these are actually for. /6, small block? Mopar?

I run RN12y, I think in my 440, so I'm guessing not big block.

Thanks
Chris

9 is colder than 12. Everything else is same.

Originally spec'd for an early 340. It is a cold plug. these would also fit a slant six but would be too cold for a non race app. your 440 would have RJ12y plugs (or another number but the letters would be the same) & a C after the Y on some of those types denotes a copper core (not sure what that is exactly but that is the definition). EDIT it might mean it is a non resistor type.

The R equals resistor, the N stands for 13/16 body in 3/4 inch reach, the 9 stands for the heat range and if it had a C after the 9 it would have a copper core center
They where used in 340 and can be use in 426 hemi motors, they can't be used in any of the later after market BB aluminum heads like the Indys, B1 or eddy and 440 sourcedue to the machining around the spark plug hole, those heads need the RC type plugs like the RC9YC. Which is the same plug with the 5/8 body
The iron OEM BB heads use the J series plugs which are 1/2 inch reach with the 13/16 socket size body

^^^ Good info

A plug with the letter "R" somewhere in the part number is a resistor type plug. Nearly every plug produced in the world today is a resistor plug, so much so that non-resistor types are usually the ones labeled.

NGK has a very informative website which goes into great lengths about plugs.

Non-resistor plugs create interference that spans a wide range of frequencies. This includes police, fire and rescue, TV, radio, CB radio, my electronic defibrillator, basically anything feeding into an amplifier that has a long run of unshielded untwisted pair wire. It affects the electronics under the hood as well.

Spark energy is definitely not steady, it acts much more like Alternating Current (AC). Add AC and high voltages together, and they quickly move out of the "intuitive" range.
I believe the interference has something to do with the shape of the waveform of the spark energy. It is much like a square wave, which consists of a series of odd order multiples of the parent frequency.

One of the interesting factoids from the NGK site is that any spark plug made after 1970 was most likely to have a copper core. This was to aid in heat transfer up the center electrode. The copper core is encased in a nickel jacket.

The phrase "Copper Core" was an advertising slogan, much like some ads for mid-'60s cars touted seat belts as standard equipment, even while they were mandated by the government.

R.

Good stuff Dog, could you repeat that please.

Years ago i called Champion, asked for an egineer, and inquired why the 1994-1995 8L V10 had 9 heat range plugs and the V8s had 14 heat range. After chatting for a bit, he more or less admitted that 9 was the proper heat range for towing duty but the 14 heat range plugs produced slightly less pollution in the cold start portion of the EPA emissions test for light duty engines.

Magnecor has a good write up about RFI from wires and plugs. I have their CN maximum reduced RFI series of wires to help out the Shortwave reception of a Becker Mexico car radio. Too bad there are almost no worthwhile international SW stations to listen to now.

It's hard to believe your telling mopar people how to decipher plug numbers. Old Champion charts are still around(ebay). Cab, how long have you been talking "plug numbers".. 50 years,60 years? I use Champion N6 to N10s on drag Hemis. R(resistor) doesn't mean a thing unless it has a radio.

I was taught to not use retracted gap plugs on any N/A gasoline motors where projected gap plugs would fit, I still do that
The coil or magneto knows exactly how much resistance it has to over come to fire the spark plugs, correct?
Have you ever ran a MSD 7 series ignition box without using resistor spark plug wires with non resistor spark plugs?
If so how did that work out for you?
My first MSD 7 missed horribly until I got the resistor spark plug wires installed on my old NHRA stocker
The other MSD earlier 404 series race boxes didn't mind having solid core wires with non resistor spark plugs, ran good, lasted a long time
I should have read the instructions on the new MSD 7 race box first before using it
That mistake caused me to chase a intermittent miss between 5200 RPM to 5600 RPM for most of a year (8 NHRA races)
I do now use retracted gap plugs on my E85 race motor with a MSD 7AL2 box and coil with resistor plug wires per many recommendations from many other E85 racers
To answer your question on my age I got the hot rod bug in 1963, I've had it bad ever since

It should be more widely known that
increasing resistance in the wires and/or plugs
lengthens "burn time" of the spark.

Resistance, inductance and capacitance of the ignition system components all matter.

Try "souping up" the performance of your computer
by cutting out all the resistors on the motherboard
and replacing them with "high performance" copper wires.

Got me laughing with that one!

Trouble is, most of us are DC guys operating in an AC world.

I second the Magnecor website as full of real information. My Magnecor wires are the nicest ignition wires I have ever handled.

R.