Where would the block be cracked if water froze? I am assuming the pass side

but none are visible,all freeze plugs(new) look good and in place. #3 cyl had water in it.

There was water in #3 cyl. Could it possibly cracked the head and not the block?

Doug that would have been my guess. And welcome to the site!!

Thanks Tom. I have access to another Z for parts so the head would be no prob. I am toying with a 5.0 swap or a Grand National turbo V6(got a complete one)

When the Z engine overheats the head ends up warping. Usually causing the head gasket to fail and allowing water into the #3 or #4 cylinder. If you had a cracked block wouldn't the water be leaking on the outside?

It could be cracked anywhere in the water jackets I guess. It hasn't been overheated,it has only been driven in his yard after installing the rebuilt motor but he didn't put antifreeze in it or drain it.

That's why I was asking since I saw no water to outside. Thought it might not have hurt the block.

If you are in coastal Ga, I don't believe it has been cold enough for long enough this winter to have that issue.