Broken valve stem

[Jlmatt]

This is my first post to this great site. I have never worked very much on engines so my mechanical knowledge is rather limited. My boat is a 1961Pearson Triton, which I acquired almost 2 years ago. It has been sitting on a trailer in my driveway all that time but now I started working on it. I removed the head and the manifold to clean the water passages and try to free 2 stuck valves. I was successful with one of them by soaking PB blaster and gentle tapping. The other is really stuck. I tried twisting it and it snapped flush at the valve guide. Now what do I do? I drilled a small hole in the center so I could put a nail and tap on it but it still does not move.
My question is: how hard can I pound on it without risking to crack the block? Or should I try drilling more with bigger bits? I don't want to damage the guide if I don't have to.
The valve is the one at the very back and there is a little bit of rust on it.
The previous owner replaced the block because at one point water came in from the exhaust. So it appeared to be a late model block with the original head and no thermostat.
Jean-Luc

[Don Moyer]

Jean-Luc,

When a valve is stuck so hard that it will not yield to tapping and rotational force without breaking, it is a signal that you have little hope of removing it by prying from below by using the top of the tappet for leverage. You reach a point where you risk damaging the tappet or the camshaft itself. You will have to drive the valve stem out with a long drift punch, possibly from the bottom upward if the fracture zone of the valve stem has developed a bend.

Unfortunately, this means that the engine will have to come out and be disassembled down to the point of removing the cam shaft and tappets. With respect to your concern over damaging the valve guide, a valve guide can be replaced rather easily. In fact, the guide may slide out with the stem if it is really stuck that hard.

Don