These anodized aluminum lifter valley vents for small block Chevy's offer positive crank case ventilation to the upper engine. Eliminates lifter valley oil drain-through to the crankshaft and resultant increases in wind-age and also eliminates debris from falling into the camshaft/lifter area or worse between the connecting rods. Unlike pipe plug or screen kits which only do part of the job. STEF's lifter valley vents provide all the functions listed. Once the OEM vent holes are tapped to 1/4" N.P.T all eight 2 1/2" long valley vents install easily via the 9/16" hex head machined at their top.