norbs, I can understand about the grooves looking small to the eye, but then that 0.080" hole they recommend also looks small to the eye
Seemed to me that they were trying to restrict the amount of oil to the drivers side lifters (I think those are the only things fed by that gallery, or are the #2, 3, 4 cam bearings fed from there too? I always forget), to force more oil to the rods and mains. I guess the lifters don't need that much oil.
Seems like if you had the gallerys joined at the back and deleted the grooves and such up front you'd accomplish the same thing; the rods and mains would always get priority over the drivers side lifters. Is that what you've got? You said the holes in the #1 cam bearing are clocked so that the passages are covered up, so there is no transfer from pass side to drivers side via the groove in the cam? Only by the grooves on the backside of the cam bearing? (you know, you could ask the guys at TA their thoughts, since they are the cam bearing providers. They should know if the grooves alone are sufficient). If you aren't using the holes in and out of the #1 cam bearing to transfer oil to the drivers side gallery, if I was you I'd try to find a cam without the groove in it, to reduce wear on that bearing.
Whatever the case, I don't see that line in the back hurting anything. While Ruggles, et al said that drilling the smaller holes in the cam bearings helped oil pressure, I'm not sure why, the lifters are going to take what they want to take. Unless those tiny holes dropped the pressure a lot in that gallery... I can see that helping pressure, if the small holes in the cam bearing made the drivers side gallery run at 15 psi when the passenger side gallery was at 25 psi... that would explain a lot. Essentially the same as putting a restriction orifice in the gallery feed passage. Your line is counteracting that, of course, but again I don't see it hurting anything. If that's how the small holes were supposed to work then maybe you lose a few psi at idle, but if the rest of your system is up to snuff, I doubt it.
Now, on the topic of pressures being the same everywhere in the system... I hate to bring it up again, but it just isn't so. Fluid doesn't move without a reason. The reason is that the pressure is higher at one end. If the pressures are the same, there is no flow. Whether it is inside an engine or in a city water system. Now the pressure difference can be small, no doubt about that. In the grand scheme of things the distance between front and back of the block is only what, 15"? Across that short a distance even a very high velocity might show only 1/2 psi drop. But that pressure drop is there, it HAS to be. I don't know about your eyeballs, but mine are not calibrated to see a half pound difference on a 0-50 psi or 0-100 psi gauge. If you put a differential pressure gauge on there I bet you'd see it though. City water system, same thing. You can have as big a pump as you want, but there *is* a difference between pump discharge and the last tap. You might have a 24" main that only gives you a couple of pounds drop over a half mile, but the pressure difference is there. As a guy that has had to survey water systems (not city water, but cooling water systems, essentially the same concept), trust me on this. If you had a 10" main instead of a 24", do you still think you'd have the exact same pressure at the last faucet as at the pump? What if you had a 6" main? Or a 2"? If not, why not? It's the exact same principle. Its just a lot harder to see the pressure difference in the big pipes.
John