Re: AC 43LS Spark plugs

Posted by Owen_Dyneto On 2007/4/13 13:04:53

Frankly I'm reluctant to rely on old plug recommendations as the changes in gasoline composition, flame temperature and propogation have changed so much. So I usually take a current recommendation from one of the plug makers. Autolite's site is among the easiest to use, and for my 56 Packard they recommend Autolite 66 for a non-resistor plug (my choice). I've also used Champion RN14YC with good luck. You don't say if your upgrade of a 55 to a 56 V8 involved changing heads but I guess you know there were different plug requirements when they went from machined to cast heads (see Service Counsellors for info). If I still had the 55 heads, I'd hop onto Autolite's site and get their recommendation for 1955.