SB-Chevy
Eight plugs block the oil return holes in the lifter valley above the camshaft, redirecting oil to the front and rear return galleries. Oil is returned to the sump area without dumping onto the crankshaft to eliminate lost horsepower due to increased windage.

BB-Chevy
Four stainless steel mesh screens are epoxied in place over the lifter vallry holes to contain debris insted of letting it enter the oiling system. Oil flow is not restricted or redirected.