So, Ive just spent the last couple of hours seaching the forum for some cross reference information on various heat ranges of spark plugs. I thought I remembered seeing a thread a year or two ago that gave a listing of a few different part numbers for US plugs that would interchange, but I wasnt able to find it.

I DID, however, manage to find a nice little chart of cross references of NGK, Autolite, AC Delco, and Champion race plugs here http://www.dragstuff.com/techarticle...reference.html

I used this site http://www.sparkplugs.com/ to get the thread pitch and heat range of the different plugs in order to see which matched up to the OEM plugs.

The problem Ive run into is that all of the plugs listed on this site with a descent heat range have a 19mm reach, while the OEM sparkers have a ~21.5mm reach. I dont know if this difference has anything to do with the OEMs being the flat, 4 electrode type and the race plugs being a overhead electrode (that would have to be cut and bent to side fire to work)? 2.5mm seems like an awful lot when it comes to something like this. Am I wrong?

Alex

 

The iridium plugs i use are overhead electrode. I have no problem with them @ 32k miles still good as new.