Excessive oil out rear-most pushrod tube

[Lonnie]

I have a restored '48 panhead and have an extremely irritating problem. The rear pushrod tube has a bad oil leak which I cannot seem to stop. As background, in order to try to increase the oil pressure at idle, I have changed the oil pump on two separate occasions, 1st one being the original '48 pump, then a '49 pump, and now a '66 shovel iron pump with the chain oiler hole
plugged. While that has been resolved with the latest pump (tho not 100%), with each change the leak at the rear tube has gotten worse. It has a rare set (never seen another) of the early aluminum-style lifter blocks but in iron (not a converted hyd. lifter set). Running knucklehead-style lifters with built-in adjusters and alum. pushrods.
I have tried every pushrod gasket known to man, made sure the sealing surfaces are slick, stretched the spring in the tube even. Nothing seems to help.
I know there is a dam attached with a screw between some of the cooling fins on the head under the pan that was a dealer install, done to resolve some over-oiling issue, but I thought that was just to keep the oil from puddling around the guides.

Help.
Lonnie (again)

(This "Be a Man, Ride a Pan" thing is killing me).

[Kojack]

I'm no expert on pans (or anything for that matter) but it seems like you may have some type of internal oil leak. An oil pump won't build pressure if there's no resistance to it. You're installing progressively stronger pumps with little change in pressure. It also sounds like the rear pushrod tube is being filled with oil. If something is causing the rear head's rocker assemblys to be over oiled the rear pushrod tube will fill up first. I'd check the rear head for excess rocker clearance or something else that would bleed off oil too quickly. I understand that there are some plugs used in the end of the rocker shafts, maybe one is missing. Then you can cleck the rear lifter block to make sure the drain slot around the lifter isn't plugged. Maybe some of the real pan mechanics can come up with some other tips.

[koanes]

You may have a problem with oil return thru the head, cylinder or case. Wrong base gasket or blockage somewhere. If just the exhaust pushrod tube is filling and not the intake, I think Kojak is on the money with his thought that the oil drain slot it plugged with carbon, a chunk of push cork, or something. I would love to know what the story is with the iron blocks, I have had a rear block in my tappet block stash for years and have never ben able to find a matching front.