What would cause low compression on bank 1? Cyl1 = 85psi cyl3 = 110 psi cyl5 = 90psi cyl7 = 100 psi. Bank 2 cyl2 = 135psi cyl4 = 150psi cyl6 = 145psi cyl8 = 150psi. Bank 1 valvetrain looks good. Bank 1 exhaust is not restricted. I know it seems unlikely but is... Login to read more.