Sup. I was wonderin exactly why its so damaging to a motor when the headgasket blows. Cus i know a lot of time people just replace em. But what kind of damage can occur when it does blow? I saw a post explaining hydrolock and kinda figured that that was what happens to motors when the headgasket blow. The reason I ask is because my moms F.O.R.D. wouldnt start and according to the shop it blew its gasket and the head is warped. They said it would be like 1000 just to replace the gasket. I figured that I could get it home, pull the head, get it milled and corrected and replace the headgasket for much cheaper. But what other damage might be done that I would have to worry about? Again I'm just wonderin this about any motor cus it would clear up a lot of questions i had concerning blown motors and such. Thanks in Advance!!

 

Its not always just the head that needs resurfacing. Usually when a head gasket blows the car overheats. When a car overheats the rings have a tendancy to fry. If water was getting into the pistons it could have done a number of things. Burn a hole in the piston, fry the rings, smooth out the cylinder walls, burn a valve, warp the head and or block blah blah blah. A lot of damage could happen. You could hydro lock the motor but that would have to be a serious leak. In most cases all you need to do though is surface the head(and its a good idea to check the block as well) and put some new head gaskets and bolts in it.

 

If the motor hydrolocked it could be any number of problems. Hydrostatic lock, hydraulic lock or hydrolock occurs when liquids, typically water, enter an engine cylinder. This can occur from a coolant, oil or fuel leak, but the chief cause is drawing water into the engine through the air induction system. Engines must employ a compression stroke to compress the charge (usually an air/fuel mixture). Liquids are incompressible, the presence of a liquid in the engine cylinder during the compression stroke generates super high cylinder pressures.

Abnormally high cylinder pressures can bend and break pistons, piston pins, connecting rods, crankshafts and ruin bearings and can crack or break cylinder heads and engine blocks.
Hydrolock may occur while the engine is running, the work of the compression stroke being supplied by engine's rotational inertia. Or a liquid may leak into the cylinder while the engine is being stored; the work of the compression stroke will be supplied by the starter motor.

In short Hydrolock=bad

Your mom's car is a different story though. If a headgasket is left blown long enough, it could lose enough compression to the point it won't even turn over.
I couldn't tell you if what is wrong with her car from here. If you aren't qualified to do it, pay somebody who is.