My daughter's 2008 TSX started running rough and few minutes later died. She killed the battery cranking it. I charged the battery and cranked it over. It sounds as though the engine spins freely without any compression. I'm guessing the timing chain either broke or jumped a couple of teeth. How likely is it that the engine is destroyed? I can buy a used (46k miles) JDM engine for it. What is a JDM? Am I better off rebuilding the head and installing a new timing chain on the wrecked engine? (About 120 k miles)?

 

JDM stands for Japenese Domestic Market.
there's no benefit from grabbing a Japenese motor...
so, yes..you are better off rebuilding the head and installing new timing chain..

check first with compression and leak down test.