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Jan 20, 2018

Oil Pumps on RB Series Engine : True or False

Tomei oil pump vs OEM oil pump

True or False?   The oil pump on an RB series engine will explode if you look at it funny?


Like any vehicle, any mechanical device, there are some flaws with the RB oil pumps. If a car was running for 25 to 27 years with the original engine, original oil pump, and it breaks in a week once a new owner has it, it might not be the car.  There are people out there that believe the pumps are made from glass, which they are not.  For the hundreds of thousands of RB powered cars in the world, there are relatively few failures, but they do fail.  Generally if they fail it is due to over revving, or shocking the oil pump.  The oil pump is driven directly from the front of the crankshaft. It has to suck and push oil, something pumps don't like to do.  At 8k rpm stock, the rev limiter protects the engine on the way up, but not on the way down. Right hand drive car in a left hand drive world. Don't misshift like these guys...

Our NISMO R32 is an early car, with an early oil pump and drive. It has several track days turning 8000+ RPM, and several drag strip days coming off the two step.  We went through more clutches than engines or oil pumps.

Often new engine builds have an oil pump failure. Most of the reason for this would be related to poor engine cleanup, or poor installation. We have seen the blocks align honed, then the oil pump not be squared up to the crankshaft. Since the oil pump is not centered on the crankshaft, it binds on the housing with every rotation. Eventually this causes a failure. We have seen several oil pump gears showing signs of blueing, which will come from poor install. If the engine builder doesn't know what he is doing, of course he will blame the engine, rather than his lack of knowledge.  If you are installing a new oil pump, make sure you check the crank for binding once the oil pump is installed.
RB26 oil flow diagram
RB26dett oil flow diagram

If you are just driving the car around normally, you change the oil, then no reason to be concerned. If you are two stepping at every car meet, pulling 9k rpm, and 35 psi, then an oil pump upgrade is probably in order. Not every car needs a Tomei pump, not every car needs a spline drive, not every car needs a dry sump.  At the low end you are a few hundred dollars in parts, plus engine out labor to get at the pump. At the dry sump end you can be near $10k in with pumps, lines, fittings, pans, filters, belts, and brackets. What you need for your setup, is up to you.

Engine Lubrication and Cooling Fluid Capacities for  Nissan Skyline

Engine Oil Capacity (quarts)
H Level4.24.34.8
L Level3.23.53.7
Oil and Filter Change~ 4.4~4.8~4.9

Coolant Capactiy (liters)

Engine Oil Pressure(kg/cm2, psi)
RB20E~1.0, 14~3.8,54~4.8,68
RB25DE~1.0, 14~3.3,47~5.3,75
RB25DET~1.0, 14~3.5,50~5.6,85
RB26DETT~1.5, 21~3.0,43~4.6,65

There are several reasons for oil pump failure not related to driving, laid out below.

Nismo #500, and the Vert
Why do the oil pumps fail?

  • Installation error. If the pump is not square to the block and crankshaft, it will bind with every turn of the engine. We have seen several failures related to new builds, align honed, and the pump dowels not being modified to ensure the gear clearance is correct. 
  • Cavitation at the inlet side of the pump.  High RPM, long draw. Pumps only like to do one thing, suck or push. You are asking it to do two, which it doesn't want to do. 
  • Bad design. The flats of the drive are at the small side of the gears
  • Going oval. We have seen the gears go oval. Mostly related to install, and cavitation. 
  • Backing plate screwings coming loose.  The backing plate screws can come loose causing a loss of oil pressure. Loctite or stake them in place when assembling engine. 

Oil pump drive

There is an early and a late oil pump drive.  The early drive only very minimally engages the flats on the oil pump gear to drive it.  You can see when Nissan went to the later style pump that the width and engagement about doubled. If you have an early crank, you should think about swapping the crank out for a later crank, or purchasing a crank collar.

Early oil pump drive
Early drive- Notice how much smaller it is than the late drive. Also notice the small shiny spot. That area is the only part that actually engages the pump.  

Notice the wear on the flat spot. Compare the width here to the early drive shown above.

Late RB oil pump drive - Notice the wear on the flat spot. Compare the width here to the early drive shown above.

Oil Pump Gears Going Oval

Jun oil pump gears showing a slight ovalness to them
This is something that we noticed fairly recently with the oil pump gears on the RB26. The inner gear on the oil pump has two flats that are driven on the crank. We noticed that we had some oil pumps that were binding. Measuring at the flats and the opposite side to the flats, the gears appear to be going oval. We have seen it in a JUN oil pump, and a Tomei oil pump.  Both pumps, when the gears were replaced with Spline drive gears, no longer showed signs of binding in the housings.

Tomei oil pump gears showing a slight ovalness

Running a narrow oil pump drive, and OEM oil pump

RB Oiling : Oil Pumps : Oil Restrictors : Oil Pan Modifications
Oil Change and Oil Filter for a Nissan Skyline GT-R
RB26dett Oil Pump Gears Going Oval: Oil Pump Failures

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