Broken ring

[defiance]

So I pulled the old 440 out of storage today - freshening up to sell to get more money for the new one   - It's basically stock, bored .040 over, but previously had a head gasket failure.  So I spent weeks trying to figure out why it kept overheating...  Long story short, when I figured out that this engine needed to be pulled out, it ended up being the catalyst for a MUCH more aggressive build starting with a fresh (unbored) block.
ANYWAY...
As I'm pulling it apart, most of the cylinder walls are essentially perfect - the engine was last rebuilt in '98 or so, but it's actually only had a couple thousand miles since then.  But one had a small up-down scratch.  Not deep at all, and I'm certain it can be honed out...  but the point being, ok, need to pull the pistons now to hone...
Lo and behold, the top ring on that piston was broken in half.  Which I'm sure is where the scratch came from...
But having never dealt with bad rings (other than just old worn out ones that start leaking oil and causing smoking), I have two questions:

1) - what normally causes rings to break?  Keep in mind, this was a low-compression, basically-like-stock build.  I actually dyno'd the car at one point and it had low-200's in hp.  Of course, that may be because it had no compression in one cylinder, but the point being it was never intended to be a strong build...  So I can't think of what could've cause the ring to break like that...

2) - What are the symptoms of a broken compression ring?  I'd guess loss of compression in that cylinder, but since the entire ring was still there (just in two pieces) and the second ring was fine, would it have been dramatic?  Also, anything to do with heat?  Or anything that might have cause the head gasket to fail (or vice versa)? 

As I said, I know the solution; I'm ordering new rings and rod bearings (figure I'm taking them out anyway, might as well replace the bearings while I'm here); I just want to further my understanding of 'what went wrong'.  Thanks for any insight!

[beedees]

Broken during installation 99.9% of the time. Detonation CAN break rings, but is very rare.....usually if thats the case, the piston is cratered.

[defiance]

hm...  no damage to the piston or anything...  That would be pretty disappointing if it were broken during installation; the guy that built it is supposedly really good

[beedees]

Sorry, it happens. I was in the business for 25 years.....don't ask me how I know.

[Rolling_Thunder]

Broken during installation 99.9% of the time. Detonation CAN break rings, but is very rare.....usually if thats the case, the piston is cratered.

   agreed...    99% of the time they are broken during assembly

[defiance]

So it's one of those things that just happens, not necessarily a sign of neglect?

heh - now I'm going to be paranoid about broken rings for the rest of my life

What about symptoms?  Is it pretty much just compression loss usually?