Correct Plugs for XPAG Engines

[Skip Burns]

Reviewing recent comments on the proper plugs for T-Series car engines, a reliable indicator is the number embossed on the top, forward right side of the head. If the number is 22592, it takes a 14 mm, 1/2-inch reach plug. Later heads had different numbers and, as far as I know, they all take 3/4-inch plugs. If you're not sure, make a small bend in the tip of a wire. Reach down into the plughole and measure it. NEVER, NEVER PUT THE WRONG PLUG INTO THE WRONG HEAD. Having said that, there is one exception. I know of several instances where 3/4 plugs have been installed in heads stamped 22592 for improved combustion. A cursory examination of an installed 1/2- inch plug in a 22592 head reveals shrouding of the tip of the plug; i.e., the plug doesn't reach far enough into the head chamber for optimum combustion. The trick is to install two copper washers between the plug's base and its OEM washer. This allows the plug's tip to extend slightly further into the firing chamber, yet still avoid plug/piston interference at TDC. Cheers, Skip (TB 0340)