Kept wondering why I was down on power. Finnaly found out. #8 cyl wall is cracked. I left the coolant in the cylinders maybe wondering if I had a ring issue. #6 leaked all the coolant by and if you push your thumb against the piston it rocks a little. Same thing with #1 it rocks some. The others are solid. It was a used shortblock. Think the rotating assy will be ok to put in a good block with new rings/bearings?

 

Sucks to hear that man. I wouldn't reuse any of that rotating assembly. If there's play when you push on the cylinders, the pistons might be no good. Time to build a 408!

 

That looks like a scratch from debris. When you get it apart, measure and check the pistons thoroughly. If anything you might need some pistons, but the rest of the rotating assembly can be used in another setup easily. Looks like a Manley piston, you might be able to get 1 or 2 replacements instead of an entire set.

Piston rock when the engine is cold is not a valid test for anything really, the crown of the piston is usually .050" smaller than the skirt area, so it will rock as that is how it is designed. The piston skirt is where you set the piston-to-wall clearance from.

 

The more threads i see like this, im starting to realize that my car has this problem. Or maybe im just paranoid :/

 

That sucks, but like Joseph said rocking pistons won't tell you anything. Pretty much all aftermarket pistons are built with some outward taper from the top to the bottom. That's to help deal with thermal expansion. Measuring them is the best way to go.