A buddy of mine had his 350 water freeze solid over the winter because a friend of his put straight water in it doing some other type of repair (instead of a water/coolant mix). The car has been sitting since then. What should we check to make sure the engine is okay? Just change the coolant and oil and start it up? I think the freeze plugs might have pushed out (will replace if needed). How potentially screwed up could the engine be? Does it need a full rebuild? Thanks!

You need to check it carefully...as you know water expands when it freezes and the block or a head could be cracked. Hopefully, the freeze plugs did their job and saved the block though!!! Good Luck.

The block could be cracked.

I'd say you should put a pressure tester on the cooling system and find out if it holds pressure or if it leaks. Track down the leaks and bypass them or repair them.

You will not have to rebuild the engine. If the block is damaged you just need a new engine.

You need to check it carefully...as you know water expands when it freezes and the block or a head could be cracked. Hopefully, the freeze plugs did their job and saved the block though!!! Good Luck.

"Freeze plugs" are actually core plugs from the casting. They are not there to protect the block from freezing. Although they do often push out from the expansion of water, they won't project the water jackets from cracking the block and/or heads. As someone else said, pressure test the cooling system before you start it.

Agree with go2fast -- many years ago I had a small block that had water rather than anti-freeze in it and it sat over the winter. When I saw the freeze plugs pushed out, I decide to just go ahead and pull the motor. When I took it apart the block had a crack in it that ran almost the entire length of the lifter galley. If I were you, I would pull the motor just to be safe.

Check along the pan rail about 1" up near the drain plug. Thats where they will usually go first, then in the lifter galley

go2fast is right on - those holes are there to facilitate removal of the sand from the casting process. I've seen dozens of blocks with airtight core plugs and huge freeze cracks. Good luck - hope you got lucky!

Any water in the oil?? You might find your answer quickly there.

Water in the oil is s asign if the engine runs. If the block is cracked externally, water wont get in the oil. Pull the engine and get it checked out. It doesnt look good.