I need some help.

Just removed the engine to do a cam and all supporting parts. After removing the heads I saw that the pistons are convered In black stuff.

The engine has like 10k miles. The heads were reused. Never touched. Could the valve seals be bad allowing oil into the cylinders?

The engine was bored .030. Someone told me I probably have piston slap. And the piston to bore clearance isn't right. I'm not an engine builder but I remember when I measured, the ring clearance was perfect. Cross hatch looks good in all 8 cylinders.

I don't know how to post pictures.

 

It could be valve seals or the valve guides also.

 

Is there a way to check valve guides?

 

If the heads are removed from the engine, look for side to side movement of the valve tip as an indication of excessive wear of the guides or the valve stem. Your machine shop would have the necessary tools to properly diagnose the problem .