when you raise the exhaust port your motor will make power at higher rpm which also means less low rpm power . If your jugs are ported your exhaust was already raised and if you add another .040" you might have to get off and push the fucker to get moving shee'll rip your arms off up top though .
get a printable degree wheel from google , glue it to something solid ,bolt it to your crank and tell us how many degrees your exhaust is open