What temperature does an engine block crack?

Answer 1

Marine engine blocks will crack when the water in its passages freezes and subsequently expands. If the passages are full of water inside an engine, the frozen water needs somewhere to go sotheoretically it makes room by cracking the block, hence making it bigger. If an engine was subjected to a constant 32 degrees over long enough time to freeze entirely that would be enough. However, the manufacturers install "freeze plugs" in key spots so they give before the block. This buys some time. A few cold nights wont crack a block, but winterize the engine with antifreeze before the long cold winter sets in.