Wont start, Engine cranks but wont start even with starter fluid

So to take it back to the start, the van was overheating but I didnt have the money at the time so I just kept adding water to it. It just died on me one day and I have not been able to get it started again. I replaced the head gaskets(there was a couple quarts of water in the oil pan), I have tested that it is in the right position, there is spark and there is fuel. So that is a compression issue correct? What could this be? I was told that I now have valve problems and should just replace the motor. I dont know why but that seems wrong to me. Even if it is a valve couldnt I replace it?