I'm about to buy a 1995 Saab 9000 cse turbo 5 speed and the guy said he did a head gasket and he turned it over and the chain "got caught somewhere" and snapped. I've never heard of this happening... is this something these engines do in assembled incorrectly? I understand there are 2 chains? I'm just gonna pull the motor and replace both and I'm gonna redo the head gasket because he obviously doesn't know what he's doing, I'm wondering what parts I should order? if I'm gonna need any special tools? thanks in advance! P.S. ill check the valves...