How can i get b out of my 2 kicker L7 12"?

i have 2 kicker 12" L7 2 ohm subs. amp is a kicker zx1500.1. 1.5 farad capacitor. 2 batteries. bigger alternator. the box i have was made specially to fit in the back of my 82 camaro so it probobly is only like maybe 1 cu ft per sub. they like quit out wen i turn it up. they kick a little but when i turn em up more they just quit out till i turn em bak down. what should i do?? some say port em???