Drilling out a broken valve guide in an old 216 head with some rust ?
I've read posts here about removing valve guides by pressing (that is what the shop manual recommends) or by “tapping”. The concern is breaking the head casting. I haven't heard much about drilling out these guides. Is that safer than pressing or tapping/pounding, or does it create more problems?
The head is from a 1947 Chev sedan with a 216 cu in engine. It had valve work at a machine shop, but the engine “kept bending push rods”. It was removed, wrapped in a cotton cloth, and stored on top of the engine, with the hood closed - for about 40 years.... It was in surprisingly good condition - lots of surface rust but no deep corrosion. All valves were seized in the guides, but most were coaxed free with repeated penetrating oil and tapping over a week. These valves now move freely, and the valves and seats mate tightly. But two intake valves were severely rusted to the guide, and these two guides (cast iron) broke when removing the valves.
I'd like to take this head to our local (small town) machine shop to clean and assess for cracks, and if ok to replace the guides (should they replace them all ?), grind the seats, and install new valves.
Because the guides may be well rusted to the head, I'm concerned that pressing them out may break the casting. Is it reasonable to ask the shop to drill them out?
Would sure like to hear the wisdom of you who have the experience.
Thanks for any advice.
Jim
PS - the head is to go on my 1950 GMC 1/2 ton with a 216 engine, which is running great (compression 105-118 psi on all 6 cylinders), but has a cracked head leaking coolant. Temporarily repaired with JB weld.
