For the most part for stock and "lightly" modded cars, all spark plug threads lead to........the stock lawnmower plug.
Spark Plug 101
SPARK PLUGS
Champion - RC12LYC
Gap to .038
Here is the breakdown for the Champion part number:
R= 14mm Thread, Gasket seat
C= 3/4 Inch Reach
12= Heat Range
E or LY= Projected Tip
C= Copper Core
CC= Double Copper (Copper core AND Copper Cored Ground Electrode)
FIRING ORDER
Driver side:
1-9 odd
Passenger side:
2-10 even
Champion “Regular Class” - Traditional #RC12LYC (what’s in there from Mopar)
Champion “Super Class” - Single Platinum #3034
Platinum center electrode, resistor plug, 14mm, 3/4" reach, 5/8" hex head, .290 core nose projection, copper core. **
Champion “Premium Class” - Premium Gold #2412
Gold Paladium performance plug, resistor plug, 18mm, .460" reach, taper seat, 13/16" hex head, extended electrode gap & core nose projection. **
Gold palladium - Gold is an excellent conductor of electricity, which makes it well suited for a performance plug. However gold is also a very soft metal, therefore the gold alloy is mixed with palladium, (a much harder metal), to form a premium fine wire performance plug with increased ignitability and durability.
Autolite Single Platinum #AP985 **
Autolite Double Platinum #APP985 **
Bosch PLATINUM #4203 **
Bosch PLATINUM+2 #4308 **
Bosch PLATINUM+4 #4428 **
Bosch SUPER PLUG #FR9HC **
Denso 5018 QJ16HR-U
GAP .035
** It is still not suggested that platinum plugs be used on vehicles with nitrous injection (from Champion’s website)
There have been instances where the platinum tip has lost its bond to either the center or ground electrode when they were used in a motor with nitrous.
The spark plug can help maintain the optimum combustion chamber temperature. The primary method used to do this is by altering the internal length of the core nose, in addition, the alloy compositions in the electrodes can be changed. This means you may not be able to visually tell a difference between heat ranges. When a spark plug is referred to as a “cold plug”, it is one that transfers heat rapidly from the firing tip into the engine head, which keeps the firing tip cooler. A “hot plug” has a much slower rate of heat transfer, which keeps the firing tip hotter.
An unaltered engine will run within the optimum operating range straight from the manufacturer, but if you make modifications such as a turbo, supercharger, increase compression, timing changes, use of alternate racing fuels, or sustained use of nitrous oxide, these can alter the plug tip temperature and may necessitate a colder plug.
A rule of thumb is, one heat range colder per modification or one heat range colder for every 75–100hp you increase.
In identical spark plug types, the difference from one full heat range to the next is the ability to remove 70°C to 100°C from the combustion chamber.
The heat range numbers used by spark plug manufacturers are not universal, by that we mean, a 10 heat range in Champion is not the same as a 10 heat range in NGK nor the same in Autolite. Some manufacturers numbering systems are opposite one another.
For domestic manufacturers (Champion, Autolite, Splitfire), the higher the number, the hotter the plug.
For Japanese manufacturers (NGK, Denso), the higher the number, the colder the plug.
Remember, CHAMPION PLUGS GET HOTTER THE HIGHER THE NUMBER, COLDER THE LOWER THE NUMBER.
Say you are starting with a RCJ7Y
if you want a COLDER plug, you would use RCJ6Y
if you want a HOTTER plug, you would use RCJ8Y
Here is the breakdown for the Champion part number:
R= 14mm Thread, Gasket seat
C= 3/4 Inch Reach
12= Heat Range
E or LY= Projected Tip
C= Copper Core
CC= Double Copper (Copper core AND Copper Cored Ground Electrode)
http://www.championsparkplugs.com/sparkplug411_champion.asp
