Two or three beers, one missed shift equals witness marks in the pisons Are the current pistons any where near the top of the block or are they way down, the reason I'm asking is to try and determine how hard the valves touched the pistons. Are any of the valves bent slightly or at all? If so I would replace all the pistons to avoid the possibly of cracks in the piston tops and skirts that you can't see, cast pistons can and will disentergrate(SP?) once they are cracked or fractured