Racing Beat Oil Cooler Line question
 

Hey guys I had a question about these lines. I went to put them on my car today and ended up snapping the fitting to the cooler (return line from the cooler to back of engine). I know the usual reason for this type of failure but I don't know if that's the case. I hand tightened the fitting and turned it about another quarter turn. I used a 10" wrench and I could not have used more then 30 lbs of force. i don't know if the fittings were defective or if maybe I over torqued them? Main reason I'm confused is the fsm says 40-51 ft lbs. Is it different for these lines? I've searched quite a bit and only found info on building lines, where to get them, etc etc. Any help is appreciated.