What spark plugs came from the factory, and what are best with a pulley mod? And what is the best way to gap Iridium plugs?
Their were three plugs that came from the factory for the ’03/’04 Cobra. They were the AGSF12FM1, AGSF22FM1 & AGSF32FM1. The ’12s’ would be first run. The ’22s’ would be the mid run. And the ’32s’ would be the latter run. I believe that 2004s got the ’32s’. The first run AGSF12FM1 Motorcraft plugs are one heat range colder than the latter two. NGK TR6 plugs are hotter than the 12FM1’s, however, these plugs as well as the NGK TR6 IX and Denso Iridium plugs seem to work well for chipped cars with a pulley. The NGK TR6 and TR6ix/TR7ix (Iridium) plugs are very popular. Note that a spark plug’s heat range has nothing to do with how hot the plug burns. The heat range refers to the plug’s ability to transfer heat out of the combustion chamber. A TR6 is a hotter plug than a TR7. Here is a link to a very good article which explains it pretty well. http://www.ngksparkplugs.com/techinf…000&country=US According to NGK, the TR7ix’s are iridium and the BR7ef’s are copper and also they are a non pr
