ok.....ive installed my battery in the trunk of my car.  now when its hot....it wont crank. i have it grounded back to the motor with 2/0 wire. is the wire not large enough? heat soak on the starter?what do you guys think?  

I just mounted my battery in my trunk and used a 2 cable straight to the frame and then a ground strap from the frame to the motor.  I've had this way for the last month and haven't had any problems.  If you need to just add another ground strap.  

This is the same setup I'm using in my Camaro too. One negative cable from the battery to the frame in the trunk. And then another ground cable from the engine to the frame up front. Been working great for 2 years. Check out this article over at Hot Rod for the right way to wire up a trunk mounted battery: http://www.hotrod.com/projectbuild/1970_dodge_super_bee_engine_install/