You dont have to use an air compressor on a 3800 to change a spring. All you do is take something, i used my dipstick, and insert it into the spark plug hole then crank the engine over by hand till you feel the piston come to tdc. then you can remove the rocker and compress the spring and the valve will at most drop 1/2-1 inch. Then just put a little assembly grease where the stem meets the guide to hold it up while putting the new spring on.