It was recomended in the DC Racing books to block oil to the lifters when using a roller cam or solid lifter cam . You teamed the gallery on one side and installed a copper tube , and then used a peeling tool that you inserted in each lifter bore, and then hammered it to round the bore back out so lifters would fit . The other side of the block , you installed a plug in the gallery . I did this on all my race 340 engines . If your engine is done this way , you could probably manage to get the tube out , but make sure you get the plugs out of the galleries , and reinstall proper ones in correct locations . Or actually , on that side with the tube , you really only need to open the hole back up at each lifter bore .