Oh no....Grooves in my cylinder wall!!!!

[PKRWUD]

Not necessarily. The cylinder gets wider the farther down you go, plus the first inch the piston travels sees the most outward force. After that, the energy is directed down. You said the marks weren't deep enough to catch a nail on, so they're young. As time goes on, the grooves should lengthen, but it also depends on what the ring looks like. How many miles are on the short block? Did it recently see nitrous or a blower? Why are you swapping heads?