Engine knock noise

Just bought a 97 trooper 133k miles with engine problems for $700. Its very clean,nice and straight. The previous owner gave me shop report.

Missfire # 6 cylinder. Spark plug had blown out of hole. Installed thread repair sleve as temporary measure. has lifter niose and lower knock. recommend replace engine.

Ive found a used engine for $700. Is it worth it to take a look at current engine or would you rebuild or replace engine without tearing it down to see whats knocking. Thanks, Steve

That lower knock could just be a bad timing belt tensioner and lifter noise could be gummed up lifters which can be cleaned or some worn parts which can be replaced. I'd dig into it before replacing the engine, just for fun.

replace the tensor and search around for some of the tick fixes (most of them are oil additives).