Make sure engine is cold, and check the torque of the plug-if you cannot get it torqued to specs (usually a low number in foot/lbs. on aluminum heads) without actually stripping the plug, adding a thread sealant to the plug may solve it. If it is stripped, you can install a thread sleave with a kit you can buy usually for 35-40 dollars at pretty much any decent parts store, and if the plug hole is easy to get to, they are not hard to install. Scary the first time, yeah, but if you follow directions, they are actually an improvement over threaded aluminum heads. Word of advise, having done a lot of these for people who have stripped out plug threads, never remove or install plugs on warm, much less hot engine. Working on a cold engine is the best chance you have of not messing something up, especially if you are shade tree. If you get something used and are doing the plugs for the first time, being careful is very important-if you turn a plug and it feels very tight, or is noisy, try spraying the plugs with deep creep or pb blaster, let it sit for 5 or ten minutes, and so slow. Once they are out, a light coating of never seaze on the plug threads will make it easier the next time, as much as 100.000 miles later.
