You can blow a head gasket or the head can crack or be warped.
Nothing good, I can tell you that. Anything from a warped head, cracked head, warped block, cracked block, and basicly, a blown engine.
Bit of a tricky one ... It all depends on the condition of the cylinder head. If the cylinder head is warped then replacing the head gasket won't solve your problem. A warped cylinder head can be skimmed (if not too badly warped). If the cylinder head is badly warped then it would be much easier to replace the head than fit another engine.
First of all how do you know your head is warped cracked or no good lets start at the beginning
Generally, engine problems such as a blown head gasket or warped head.
Top of the engine (head) damaged by overheating and bent so it does not seal properly
A bad head gasket , a warped head usually from overheating , would allow engine coolant into an engine cylinder
engine coolant getting into an engine cylinder from a bad head gasket , cracked or warped head
bad head gasket , warped or cracked head
engine coolant is getting into an engine cylinder , from a bad head gasket , warped or cracked head
The head, along with everything above it, will have to be removed. If the engine overheated then the head could be warped as well.
If the engine has gotten really hot, not long at all. If you're having overheating problems, you may have a warped head and/or a leaking head gasket.