i have a sbc crate motor with about 30 hours on it total. the number 8 plug was black and overed in carbon and i noticed it started using oil everytime i took the boat out. i did a compression check and all cylinders were 140-150, number 8 being one of the higher numbers. i pulled the heads and all cylinders looked perfect with grayish color, except number 8. it was caked with carbon. the engine never smoked and after inspecting the valves for that cylinder, it didnt look like the guides were worn or had oil getting past them. there was no scarring in that cylinder, still had crosshatching in it.
i want to put a cam and heads on it this winter, this engine has very low hours on it, but dont want to blow it up. it didnt do this until the last 3 times i had it out. it gets run hard and had been spraying 150 nitrous to it with cast pistons (i know), if i chipped a ring land or something of that nature, would it be obvious without removing piston? would the compression be down on that cylinder. any advise? if its not scored could i drop in forged pistons and run it? need to be honed anyway? is there anything else it could be, other things to check?