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Without the halo girdle in place, the windowed main webs are clearly visible. Note also the oil restrictors installed in the main bearing saddles. There are more restrictors in the lifter bores (an absolute necessity when running a solid roller in an Olds) and drilled lifter galley plugs (front and rear) to lubricate the timing chain and distributor gear (respectively). Also, the oil pump passage was ported, and the Melling pump received some of PolyDyn's anti-friction coatings too. Oil control is absolutely critical in a performance-bred Olds, and doing it right is key to keeping engine oil limited to the valvetrain and in the bottom end where it's needed most. The block's final bore dimension was 4.381-inches.