The OHC oiling circuit is unique. Those two threaded and plugged holes in the head are for the lash adjuster oil gallery. The pressure in that passage MUST be held to 10 - 15 PSI, no matter what you are getting at the oil pump. Piping oil into this passage will be destructive to the engine unless you have an in-line 10 - 15 PSI regulator.
The "hour glass" that Miles refered to is the oil pressure regulator tube in the cylinder head. It is in-line with the oil flow between the oil pump and the camshaft. The camshaft has holes in each lobe that are actually metering holes. The cam is designed to "spray" each of the followers. The oil flow through the camshaft is used to determine the pressure in the lash adjuster gallery as the oil flows through the pressure regulator tube.
The oil pressure regulator is VERY sensitive to the pressure coming from the pump. Too much pump pressure is a very bad thing; too little isn't nearly as detrimental unless it drops below 10 PSI.
The factory specs on the OHC oil pump pressure is 31.0 +/- 5.0 PSI.
There is no additional port in the head nor the camshaft housing that allows you to pump more oil to the top end. Internally, it looks as if the engineers at Pontiac were going to take main bearing oil pressure from the mail gallery and run it to the camshaft housing around the second-to-last head bolt on the passenger side. This is one of the places we've been investigating as a possible location for additional oil flow to the camshaft WITHOUT having an external pipe or manifold.
To keep the top end happy, make sure the cam is thoroughly cleaned out. We clean out the main oil passage with a shotgun brush and lacquer thinner. Each lobe metering hole is a .040" (1.0 mm) diameter hole with a slightly larger pilot hole (the dimension escapes me at the moment). These should be cleaned out by hand with a 1.0 mm drill held in a pin vise and turned by hand. Making these holes biggers will cause too much oil to collect on top of the head. If you have weak valve seals this will result in excessive oil consumption.
Excessive clearance between the cam journals and the cam housing (caused by wear) will have similar results. Jerry Woodland had a run of 4-Bbl. cams made with slightly over-sized journals that reduced the problem. Others may still have these cams around. We've developed a couple plating processes to do the same thing; one for the cam and one for the housing. (We also have similar approaches to the oil pump housing and gears, but that's another thread.)
I'm sorry to hi-jack a thread which was obviously for a V-8 oil pump. For that application, the Melling 54-D is your best bet. If you insist on a high pressure oil pump that will simply wear out the distributor gear, go for the 54F.
Believe it or not, the hole in the block that lines up with the oil pump is usually in the wrong place, and should be enlarged and chamfered when you do a rebuild.
