It all depends on the manufacturer of the plug as the marking are unique to them. Here is a link to the table for NGK plugs: http://www.ngksparkplugs.com/tech_support/spark_plugs/faqs/faqcode.asp?mode=nml
AC in AC Delco Spark Plugs stands ALBERT CHAMPION. Alberta Champion lost control of the Champion Spark Co in 1908 and then started AC Spark Plug Co. Ac was bought out by General Motors in 1909. Reference Wikipedia --Flint East
If you mean single Roman letters, they can either stand for numbers or abbreviations.If you mean single Roman letters, they can either stand for numbers or abbreviations.If you mean single Roman letters, they can either stand for numbers or abbreviations.If you mean single Roman letters, they can either stand for numbers or abbreviations.If you mean single Roman letters, they can either stand for numbers or abbreviations.If you mean single Roman letters, they can either stand for numbers or abbreviations.If you mean single Roman letters, they can either stand for numbers or abbreviations.If you mean single Roman letters, they can either stand for numbers or abbreviations.If you mean single Roman letters, they can either stand for numbers or abbreviations.
The unknowns or variables
ID1232132123's answer is: Albert Champion Doug's answer is: Alternating Current
the R stands for Resistor. It is a resistor plug.
Go to the following site (Champion) with the link supplied and at he bottom of the page look at "Manufacturers numbering system" for an explaination. http://www.championsparkplugs.com/sparkplug411.asp
Remove the spark plugs, dump in some 2 cycle oil over each piston, replace the spark plugs, turn the engine over 1 or 2 times, Let the Jet Ski stand for a while.
if your talking about the vin, they represent a variety of things about the vehicle.
X V D C in roman numerals
The passenger side spark plugs are accessed by removing the R/F tire and inner fender well. Make sure to place vehicle on a (jack stand, in park, chock the rear tire) and not just the jack. With the inner fender liner removed, you will be able to see the spark plugs. Gap is .052-.056" 13lb-ft of torque.
Variables are letters that stand for numbers x=5 y=3 j=4 J+X = 9
The letters stand for the German Quotient and Zahlen.