My spark plugs are kissing the top of the piston dome. I have a TF A460 head with pistons that were supposedly designed for that chamber. The plugs are hitting just to the point of pushing the ground strap to the center electrode. I had Autolite 3923 plugs installed. I am looking for a plug that doesn't have the porcelain sticking out of the plug, thus making the plug a bit shorter. I planned to try the NGK R5673-8 plug. From the photos it looks like it is a possible cure. If I cannot find anything shorter I will have to put a 14mm copper washer under the plugs. Does anyone have any recommendations?