4.4 timing chain
 

I have an 540 I that has 120 k with a blown timing chain. My question is repair it or replace the whole engine. Are the heads wrecked what else is gone wrong inside. not sure what is the best move. could use some advice

You most likely need to remove the cylinder head and check the valves. If the timing chain snapped, some of the valves probably hit the tops of the pistons. This is one of those things where removng the heads is the only way you're really going to get a definitive answer to the problem.