Hi Bob and all, Thanks. It is the temperature of the exhaust manifolds and heads that is of primary concern and not the working cooling capacity of the radiator and cooling system. Those with exhaust manifold gasket replacement issues should be the first to think about these cooler plugs. My original fix was electronic ignition with a remote control where I found myself retarding the timing to deal with pre-ignition and poor gas especially on road trips where lower and lower octane was my only option. This previous fix caused multiple EM and VC gasket replacements. It also contributed to the early demise of a rebuilt engine after only 22,000 miles. Valve guides started to leak bypassing oil, 2 "black death" cylinders. EM and VC gasket replacements were always repetitive issue. The engine was rebuilt to the original 10.1:1 specs with no 99 octane gas to run in it. Another new fix was to water heat/cool the crossrams like the 300-F Gran and 300-H rather than have the super heated exhaust gas boil the ethanol containing gas. But that is the subject for another "College of Hark Knocks" treatise. Tony [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/