Jun 11, 2014 at 04:52 PM
My procedure for crank installation has always been to install the crank arm bolts as tight as I could and then retighten after 50 miles or so. This bolt gets more torque than any other on the bike, but I never used any special wrench or extra leverage (unlike removing bottom bracket cups where I have an extender). One set of campy crank arm bolts came with some blue loctite on them from the factory. This doesn't seem like a bad idea, especially in your case where they have already shown a predilection to come loose. Use blue (removable) not red (permanent).
https://www.youtube.com/watch?v=ot0Cxmk2aa4#t=67