Advancing Cam and cylinder pressure

Hey guys, so i finally know how to degree a camshaft my question now is, my buddys slant 225 has a 268 duration clifford camshaft headers 4 barrel all that nice stuff. but he is only cranking out 120PSI at each cylinder evenly so im guess his compression ratio is around 7:8- 8:1. Motor is over cammd not much low end but decent top end but i was telling him what if we advance that same camshaft 4 degrees what would the cylinder pressure rise to? Slants need more torque. My question is if we advanced his camshaft 4 degrees would he be able to build at least some decent pressure or should we just start milling that head