Modern Engine Blueprinting Techniques. Mike Mavrigian

       With the intermediate shaft and pump in place during test fitting, verify that the intermediate shaft has a bit of vertical endplay. If it’s too long, this places stress on the distributor and pump.

      If you’re dead-set on smoothing the rough cast surface in the lifter valley, simply spend a few hours with a bunch of abrasives on a die grinder. That way, the Glyptol doesn’t contaminate the engine over time.

      Various specialty shops offer excellent oil-shedding coatings that provide a slippery surface to speed up oil travel. This type of coating can be applied to crankshaft counterweights, rods, the inside walls of the oil pan, and the inside wall of the timing cover. This application also helps to sling off oil from rotating parts to reduce parasitic drag.

      With that said, for a street engine, don’t mess with any of these mods. It’s a waste of money, and chances are high that you’re not going to see any benefit. For a race engine, though, anything you can do to speed up oil return and reduce oil-cling drag from the outer surface of rotating parts is a good thing.

Intermediate Shaft

      If your engine uses the distributor to drive the oil pump, an intermediate shaft provides the connection between the distributor shaft and the oil-pump input shaft. For performance use, opt for a high-quality aftermarket shaft made of hardened steel or chrome-moly steel.

      The shaft has either a male hex profile or a slot at one end and a drive tang on the opposite end. The slotted end engages to the distributor and the male tang end engages to the pump. In most designs, the intermediate shaft must be installed from the bottom of the block. The shaft is likely be designed to keep itself captive in the block, so that it can’t be accidentally pulled out during a distributor removal. If the shaft has a hex body along the full length, it likely includes a stopper clip that prevents it from pulling up through the top of the block. Be sure to install the shaft before installing the pump.

      During test fitting, with the block upside down, install the intermediate shaft and the oil pump. Carefully engage the pump-driven shaft to the intermediate shaft. Snug down the pump with its mounting bolts. You should be able to wiggle the shaft up and down in relation to the pump’s driven shaft. A bit of vertical endplay ensures that the shaft isn’t in a bind, placing undue pressure on the distributor and pump. Endplay clearance of around .060 to .080 inch is typically acceptable.

High-Pressure High-Volume Pumps

      Bearing clearances create restriction to the flow of oil, which creates pressure. The oil pump produces oil flow and is regulated to promote pressure. Larger bearing clearances reduce pressure and flow. In turn, a pump with higher volume and higher pressure is required. Oil viscosity is also a factor. In very general terms, lower viscosity oil or lighter weight oil needs tighter bearing clearances. Larger clearances are better suited to higher viscosity oil.

      About 10 psi for every 1,000 rpm is the desired goal. It’s better to have higher oil volume and acceptable pressure than low volume and high pressure. If your oil pressure starts to drop at high RPM, it’s an indication that a higher volume pump is needed. If you don’t have enough volume, you can’t generate enough pressure. Want more pressure? You need more volume. If you’re running loose bearing clearances, say, in the .0035- to .004-inch range, you definitely need a higher volume pump in order to create more pressure.

      A higher volume pump moves more oil under pressure. Pressure drops occur as the oil leaks past the bearings. You want enough flow to keep up with the pressure loss. Any additional pressure (after overcoming oil leaks) causes the pressure relief valve to open and dump excess oil straight back into the block.

      In a gear-type oil pump, oil pump gear length affects volume. The larger (longer) the gears, the more volume. Pressure regulator springs (which can easily be changed) allow you to adjust when the pump’s bypass valve opens (valve opens earlier, lower pressure; valve opens later, higher pressure). For example, Melling’s small-block Chevy M55 standard volume/standard pressure pump has 1.200-inch-long gears and is regulated at 55 to 60 psi. The M55A standard volume/high-pressure pump has 1.200-inch-long gears and is regulated at 75-80 psi. The M55HB high-volume pump, which has a 1.500-inch-long gearset, is rated at 70 psi.

      If pump pressure is too high and the engine has tight bearing clearances, the pressure rises until it finds an escape path. A pressure relief valve in the pump releases pressure. Otherwise, pressure can rise to the point of bursting an oil filter. Certain engines can benefit from a high-volume pump, such as old Ford big-blocks that have cam-bearing priority oiling, which tend to starve the mains.

      In a nutshell, if the engine is modified from OEM stock form, a high-volume pump should probably be your choice. In a stock engine that doesn’t need higher volume, you could do more harm than good, since you may be bypassing oil constantly, which increases oil temperature. In a dry sump system, it’s easy to obtain more pressure, since you don’t have a weak intermediate shaft to worry about (some dry sump systems run as much as 90 psi).