Pacbrake upgrade 60 psi valve springs, sold in a set of 6. **2 sets needed to do all 12 valve springs if you want to run 4000 rpm.
"PacBrake strongly recommends installing heavy duty (60 psi) exhaust valve springs with their exhaust brake on 1988-1998 12 valve Dodge Cummins for optimum braking power. The factory exhaust valve springs are not rated to retain the pressure the PacBrake puts forth on the springs."
ALL PRICES ARE IN CANADIAN DOLLARS