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Step 1. Completely disassemble the pump, inspecting every piece for unusual machining marks, burrs or casting irregularities. This includes the removal of the plug that secures the oil pressure spring (pry it out or drill a small hole and use a slide hammer to remove it)
Step 2. Secure the pump housing in a vice with soft jaws, and carefully radius and blend the oil port with a Dremel or porting tool. The port-to-block exit should be ported out to the diameter of the gasket.
Step 3. Mic the thickness of the two rotors and lap the thickest piece on 180-grit wet/dry sandpaper until the two pieces are matched in thickness.
Step 4. Install the rotors in the housing and check the clearances as follows: rotor to rotor .003" to .006"; rotor to housing end .002" to .004"; rotor to housing, internal .006" to .011".
Use a rotary flapper wheel to increase clearance on the inside of the outside rotor to increase clearance on housing for the outside rotor or to increase clearance on housing for the outside rotor. To decrease clearance on rotor to housing end, lap housing on 180 grit wet/dry sandpaper. Do the same to increase clearance except sand the rotors. Take your tim, and check clearances often. It's a lot easier to take more off than to add it back. Make sure the sandpaper is on a flat surface and use generous amounts of water or cutting oil.
Step 5. Once the proper clearances are set, use a dremel or high-speed rotary file and put a slight chamfer on the edges of the rotors, both top and bottom.
Step 6. If you have the bucks and the time have the rotors coated with one of the slick processes provided by HPC or Poly Dyn. This will significantly improve the life of the oil pump. If you are a road racer this is particularly important to you.
Step 7. Lap the inside surface of the end plate on 280 grit wet/dry sandpaper secured to a flat surface. Alternately, valve lapping compound on a flat steel plate or thick piece of glass can be used. It is very important to get this piece smooth and flat.
Step 8. Clean all pieces thoroughly with Tide soap and a bottle brush. Flush all pieces with plenty of water, then rinse with clean varsol or spray with a water displacing fluid like WD-40.
Step 9. Reinstall the stock oil pressure spring. Shimming the end with two (2) 3/8" SAE washers. This will bring the oil pressure up to 100 PSI cold. A new plug should be installed. These are generally available at any aut parts store that carries Dorman Freeze Plugs.
Step 10. Reassemble the rotors, coating each generously with petroleum jelly. This will ensure immediate priming.
Step 11. Install the end plate using grade 12 bolts that have been drilled for safety wire. Safety wire the bolt heads.
Step 12. Clean the pump-to-block mating surfaces with lacquer thinner. Install the pump to block with a new gasket using grade 12 studs with nuts and bolts that have been drilled for safety wire. When installing the oil pump be sure to include a new competition oil pump driveshaft. This is cheap insurance against high-rpm failure.
The oil pump driveshaft has a retainer disc on the distributor end that prevents the shaft from being pulled out of the pump when the distributor is removed. Failure to observe the correct installation procedure (retainer end into distributor shaft) will become apparent the first time you attempt to remove the distributor and the shaft takes a bath in the oil pan. When the pump and shaft have been properly fastened, recheck the pump shaft one last time and then safety wire the pump to the block nuts and bolts.
