No, a battery will never increase horsepower it's simple physics and principles of engine operation. Take your car to AutoZone and let them hook it up to their electrical system tester, they do it free and it tells you alot of things. Check out
http://www.summitracing.com , Optima sells several small, powerful batteries. Also, I'd suggest moving your battery to the trunk, it makes the 240 have ALMOST 50/50 weight ration.