It is all about oil control. In the case of drilling and installing the tube, it is about a controlled oil bleed. This is normally done as a race modification.
(READ! High RPM) Once the tube is installed and peened, you’ll need to drill a hole in the tube (debur the drilled hole and the peened tube,) to control how much oil is bleeding out of the hole. From what I remember, (what I read others did...) the hole is .060 or less. I’ll let the actual engine builders take it from here.
You could install the roller cam without this mod, however, spinning the RPMs up isn’t what I would do. Where the limitation is, I don’t know.
