engine mounts?

I noticed that the driver's side engine mount's main bolt (the huge one that you can get to from underneath the car) was loose. I tried to tighten it with a 1/2" breaker bar but had no luck. I soaked the heck out of it with WD-40 and let it sit for a few hours...I beat on it with a hammer...tried to tighten it again...nothing will budge the darn thing! And it's a fairly new motor mount, only 20,000 miles on them. I replaced them both when I put the new motor in just a few years ago. The bolt & nut still look like new, no rust or corrosion. I was lifting up the right side of the motor with the big bolt even moving up and down a little in the slot it goes through in the chassis, and nothing will budge. Even tried to loosen it some, and then tighten it. Still nothing. Any clues on how I can crank this engine mount down tight with out using a cherry picker to lift, or move the motor around some? I'm stumped.