Cast iron is funny stuff- - - - -push on it and it breaks- - - - -hammer on it and it bends. That's how a cast iron crankshaft is straightened after it's had a journal welded. Suspend the shaft on V blocks, find the high spot, and thump it with a lead hammer. Press on it and it will crack or even break. The accepted way of removing and installing valve guides has been with an air chisel and the proper size driver for as long as I've been doing engine machining- - - -a bit over 60 years. I'd much rather salvage an unbroken valve guide by installing a bronze sleeve and reaming the sleeve to fit than stressing the head by trying to replace the guides. The guide liners and reamers to install them are on Ebay for a lot less than a machine shop will charge you, especially one that has a bunch of new equipment to pay for.
Jerry
