I believe that Champion either changed their spark plug numbering system or their recommended plug type sometime prior to 1979 and so current plug types differ from what is listed in the FSM. What used to be J12Y became J14Y and what used to be XJ12Y became RJ14Y. These would be used on New Yorkers, Imperials etc. The J10Y or XJ10Y specified for the 413 high performance engines in the letter cars became RJ11Y. This information is from a Champion publication I have from 1979. Carl Bilter _____ From: Chrysler300@xxxxxxxxxxxxxxx [mailto:Chrysler300@xxxxxxxxxxxxxxx] On Behalf Of Ronald Kurtz Sent: Friday, February 18, 2011 3:36 PM To: Jonny Mattsson Cc: chrysler300@xxxxxxxxxxxxxxx Subject: Re: [Chrysler300] Spark Plugs Hi, Jonny: Can you be more specific about the year and application of your 413? According to my files, A42 is equivalent to a Champion J12Y (the lower the Champion number the cooler the plug, it's ability to transfer heat resulting from combustion to the cylinder head quicker than a "hotter" plug. Cooler plugs are used in high performance engines.) Champion specs for a 413 list a RJ14Y for standard applications and a RJ11Y for high performance applications. A J10Y or A32 is recommended for a 1959 300E. For your info: R = Resistor plug J = First prefix letter for thread size - thread reach (3/8 inch) and hex size ( 13/16 inch) 14 = Heat Range Y = Gap style - protruding nose Since R,J and Y are given for a 413, the heat range is determined by application. If you run your 300 frequently at high speeds, a cooler plug is recommended. If you drive the car occasionally, I would suggest a hotter plug. Please advise the year, car and carburation: 1 or 2 4-barrel carburators. Maybe we can zero in on the right heat range for you. Other, more experienced club members may have additional or better information. Best regards, Ron Kurtz E# 292 ________________________________ From: Jonny Mattsson jonny.mattsson@xxxxxxxxxxx <mailto:jonny.mattsson%40hotmail.com> quicker To: chrysler300@xxxxxxxxxxxxxxx <mailto:chrysler300%40yahoogroups.com> Sent: Fri, February 18, 2011 3:01:50 PM Subject: [Chrysler300] Spark Plugs Hi group, Some time ago,spark plugs questions has been asked,guess I delete them. However,the 413 engine specifications says Auto-Lite A-32 or Champion J-12Y. I have a package of Auto-Lite A-42. Can I use them? or what is your choice today. Jonny Mattsson Sweden [Non-text portions of this message have been removed] [Non-text portions of this message have been removed] [Non-text portions of this message have been removed] ------------------------------------ To send a message to this group, send an email to: Chrysler300@xxxxxxxxxxxxxxx To unsubscribe from this group, send an email to bob@xxxxxxxxxxxxx or go to http://autos.groups.yahoo.com/group/Chrysler300/join and select the "Leave Group" button For list server instructions, go to http://www.chrysler300club.com/yahoolist/inst.htm For archives go to http://www.forwardlook.net/300-archive/search.htm#querylangYahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Chrysler300/ <*> Your email settings: Individual Email | Traditional <*> To change settings online go to: http://groups.yahoo.com/group/Chrysler300/join (Yahoo! ID required) <*> To change settings via email: Chrysler300-digest@xxxxxxxxxxxxxxx Chrysler300-fullfeatured@xxxxxxxxxxxxxxx <*> To unsubscribe from this group, send an email to: Chrysler300-unsubscribe@xxxxxxxxxxxxxxx <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/