Head studs: how broken is broken?
 

Today I managed to remove the first two studs from my block with only a moderate amount of grunting. But when the second one came out, I noticed that it appeared to be sheared-off at the end. On further examination, the first one looked sheared-off also. The second shear looked fresh; the first looked like it had been like that for a while. Neither sheared off flush: they both had to be unscrewed from the block once they became loosened.

Both studs have about 5 of the coarse threads remaining (the block end). Both measure a little above 2.5 inches, and I see that the ones Moyer sells are 2.75".

So I have two questions: should I drill out whatever is left, or is 5 threads deep enough to just mount new studs in the existing holes? And if I do drill them out, will I see a cavity down below? I think I read that they extend into the cooling passages, so would I see that?

Fortunately, this is a leisurely rebuild and I'm in no hurry. But any advice on best practices, and best chances for success, would be appreciated.

Pictured below are the studs, including an end-on view of the one that looks like the shear is not fresh.

https://www.moyermarineforum.com/for...pictureid=2141

https://www.moyermarineforum.com/for...pictureid=2142

Were they close to the exhaust manifold side of things?

Yes. As I face the engine from the manifold side, these were the two left-most studs, at the manifold/flywheel corner of the block.

I will let the boss explain, answer #2:

https://www.moyermarineforum.com/for...19&postcount=2

All your head bolts but one should end up in the water jacket. So if you see something at the bottom, it should not be there. Based on previous discussions, I would assume that your studs are not broken, just very corroded from being in contact with salty water, and what you think could be the bottom of a broken stud, is just solidified crude/goo/rust.
I would recommend first to take a screw driver and a hammer, and bang whatever is at the bottom of those holes. 90% chance you will go through that bottom crap and end up in the water jacket

Studs are generally considered usable until they corrode down to about three threads left. At that point, it is highly likely that they will strip out under torque.

Thanks Edward. I've heard that "three threads" number. I'm planning to use new studs, so I'm more worried about the holes, and whether I can just put the new studs into a hole that might be obstructed.

Right you are! I used a thin metal rod and a light mallet to tap the hole in the corner, and it broke right through. The hole to the right of that yielded a little, but didn't seem to go anywhere straight down, though I was able to poke through to the oblong cooling passage next to it. Obviously those two need to go somewhere else besides connecting to each other. I'll look around for a diagram of the cooling passages.

Thanks!

OK, I took two more studs off this evening. They came off pretty easily...leaving their tips about 5 threads deep down in the block [EDIT: what I mean is that I have a hole five threads deep, and at the bottom of that hole is a bit of broken stud]. So it looks like I'll be getting some left-handed drill bits. Doesn't seem terribly concerning at the moment. I'm just glad the engine's not in the boat!

I'm using a half-inch socket with a long handle. Any thoughts on whether it's better to use something smaller so I'm less likely to overpower it? I guess the logic would be that if a smaller wrench doesn't move it, I'd add some more penetrating oil and time rather than breaking it. Just a thought.

In another thread from long ago, Mr. Moyer said:

But I am seeing something very hard and grey at the bottom of these holes, and the studs definitely have a sheared-off look to them. Hmmm...

https://www.moyermarineforum.com/for...pictureid=2143

If I understand this, you have a small piece of broken stud at the bottom of the hole? Rather the trying to unscrew it all the way up , can you just screw it down and out into the water jacket?

Great. Good luck for the rest

as underlined by Don:
"""2) Can I assume there are blind holes there (in certain stud holes)?
The only cylinder head stud hole that does not enter the water jacket is the one in the center of the head on the reversing gear end of the engine. This is the stud hole that one of the coil bracket bolts intercepts.""

Generally they come out. Gently working them back and forth, both directions is a good policy removing any bolt you think might be rusted in place.

That might be easier, but I don't know anything about that cooling passage, how big it is or where it goes. Shouldn't I be worried about getting a chunk of metal in there where it can't be retrieved?

https://www.moyermarineforum.com/for...pictureid=2144