Alright i'm sure this issue has been covered, but since the search is broken I guess i'll ask again cause its driving me crazy. I've got a 355 block with forged pistons in it. I'm getting ready to bolt the heads on but I want to make sure my engine isn't toast before I even start. The problem is that I can actually move the pistons back and forth within the cylinder. It's not a lot of movement, but I don't know what is an acceptable level. I have read that forged pistons expand in the bores more when they are heated, so they will have a little more movement than cast pistons when cold. How do i measure the movement, and what is an acceptable level so that the engine will run right and not be burning oil due to excessive wear on the cylinders, or the rings?

 

Check skirt clearances with a flat feeler gauge.