Mopar Small Block Solid Roller Lifters for 59 Degree Race Block - New

There is no need to block the oil to either side of the lifter bores if the parts you are using, including the lifters work well together. It depends on the rest of your combination to be sure.

However like any type of lifter, that depends on several factors including the cams lift, rocker arm ratio and the blocks lifter bores condition. Does the cam lift expose the oil band in the lifter, which is more likely as lift grows and if the blocks top of the lifter bores are chamfered from the factory (exposed more lifter at the top), and how worn are the lifter bores.

Blocking/reducing the oil to both tappet banks by bushing the lifter bores or blocking the oil to the tappet bores will certainly maximize oil to the rotating assembly and eliminate oil bleed volume and pressure loss from the lifter bores.

These rockers do have oil band recesses FYI which can be seen in some of the pictures.