Stef’s stainless steel thread in Oil Restrictors with inverted
hex are a necessity for late Bowtie blocks, Rocket Olds, Darts, Merlins,
and BBC because they install flush with the back of the block. These
restrictors reduce the lifter / rocket arm oil supply to a 060"
diameter hole and cuts oil volume by more than 70%, diverting it to
where it is needed most - the main and rod bearings. These restrictors
are intended for use with rollerized rocker arm assemblies and solid,
roller or mushroom lifter combos. Parts #7225 includes 3 restrictors
for use with the Rocket Olds. Never use with hydraulic type lifters.