Oldsmobile Oil Restrictor Main bearing oil gallery restrictors
Main bearing oil gallery restrictors reduce oil supply to the top end of engine. set of 4 restrictors for No. 1, 2, 3, 4 main housing bore oil holes leading to the cam bearings. Install restrictors with a 3/8 drift punch, knurling provides an interference fit, use with loctite. Will work with 307-455 EXCEPT 403 engines