One of the most challenging valve guide changes I've done was on an air cooled Porsche 914 with six individual cylinder heads tied together with two overhead camshaft carriers. The bronze guides were .008" bigger diameter than the holes in the aluminum heads they were supposed to fit. I made a special driver that would seat the guide at the proper depth in the head when it was driven home, and put the guide and the driver into a freezer overnight. Next morning, I'd heat the head with a torch and drive the guide in quickly. "Rinse and repeat!" It took 12 days to get all the guides installed! I was on my own with that one, as none of the machine shops around town would attempt the job!
Jerry
