i have a 1997 grand Cherokee he has about 300,000 miles on him I am currently over seas and my family is telling me the mechanics say the top of the engine needs to be replaced. I don't quite know what that means I don't have the named parts yet all they are telling my family is the top engine, when it starts up its fine but after running for a while blows black smoke and runs rough when on the road for a bit. I don't know how much this is going to cost to fix yet and go home in march I'm thinking of just replacing the whole engine i know he is a old jeep but I love him and don't want to give up. my question is dose anyone know what Cherokee engine years are swappable like can i put a 95 engine into my 97?

 

top end likely means the head, perhaps pistons too? with 300k miles, a top end job is likely not the best idea, as the bottom end ( rods, crank, cam) are likely nearly worn out. at 300k, a new motor is probable the thing to do for long term reliability.