Yes, it's a square plug...unfortunately (Ifound out the hard way) it is slightly smaller than a 1/2" drive, and very soft steel! I was reluctant to use heat because I thought I had read somewhere that it was risky around a cast head. Of course to make things more interesting, it is only about an inch behind the #4 plug, and under the cowl. Guess I'll try the PB Blaster. The other method I tried was to run the engine until the head was hot and added liberal doses of liquid wrench....Obviously to no avail!
