Broken Piston Ring Found During Tear Down

When I rebuilt the first 340 in my 65 Barracuda, I found five broken rings when I took the motor apart. It ran well (just a street car daily driver), but did have a lot of blowby. The motor had well over 100K on it (had the car since 68, 340 since 73), so I think it was high miles and repeated high rpms that did the trick. Have not encountered any broke rings since.