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Jan 23, 2011

RB26 Oiling : Oil Pumps : Oil Restrictors : Oil Pan Modifications

The oil pump is the engines heart. Oil is its blood.  Carrying good stuff to all the parts in the engine, taking bad stuff away.  If the heart fails, the engine fails.  In the case of an RB26, when something goes wrong, you normally have a rod exit the block. When that happens, you end up with a lot of scrap metal. To avoid large, expensive pieces of scrap metal, you should read though a few of the items I have posted below.

This is what happens when you spin a rod bearing at 8,000 rpm on the road course
That same rod, which is usually #2 due to oil, also took out the oil pan. Trash, everything
  • Oil pump
  • Spline drive oil pump gears
  • Oil restrictor
  • Oil Jet Squirter
  • Oil pan baffle plates
  • Oil pan modifications
  • Oil pickups
  • Oil drain back
  • Accusump
  • Cam Cover
  • Catchcan
  • Dry Sump - Street car 

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

Oil flow diagram for RB26dett 

Oil pump

A cool fact about the oil pump, its not generally possible to replace in the car due to the oil pump relief valve being in the way. Also to get the oil pan off, you need to drop the subframe. When you drop the subframe, nothing supports the engine.

Its a much easier job to take the motor out. A few people have changed them in the car. I have changed them in the car, but after the rig supporting the motor slipped one time, I will never do that again. 450 lbs of motor crashing down on my head is not how I want to die.

Why do the oil pumps fail?

  1. 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. 
  2. 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. 
  3. Bad design. The flats of the drive are at the small side of the gears
  4. Going oval. We have seen the gears go oval. Mostly related to install, and cavitation. 
Types/Brands of pumps

  • Stock
    • Probably lasted 25 or more years
  • N1
    • We have had lots of N1 failures, we don't see them as an upgrade
  • Nismo
    • Not the same as the N1 pump. We ran the Nismo on the R34 race car, it is a good pump
  • JUN
  • Broken Jun gear at the flat
    •  Some people swear they are strongest, they would be wrong. 
  • Greddy
    • Had failures
  • HKS
    • Good pump
  • Reinik
    • Strong gears. Group A cars used Reinik/Reimax
  • Tomei

    • Tomei Oil Pump
    • Largest gears. Three piece gear. 
  • Dry Sump

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. 

Late drive - Notice the wear on the flat spot. Compare the width here to the early drive shown below.

This is a "late" oil pump drive on an RB26 crank. Notice the wear area on the flat. 

Spline Drive replacement gear set 
Spline Drive Gear installed on RB26 crankshaft

The Spline Drive gear set was launched in 2014 after a long R&D process to offer a product that not only improves the over all strength of the pump gears as upgrades for the N1 and OEM pumps, but also changes in the way in which the gears engage with the crank. As per Toyota’s 2JZ GTE engine the best solution would be to incorporate a spline engagement which would totally eliminate the underpinnings of Nissan's troublesome flat drive design.

The RB26 is a legendary engine in its own right and an iconic powerhouse amongst enthusiasts and tuners all over the world. One aspect of the engine that is considered its Achilles heel is certainly the oil pump. Over the years there have been reports of numerous failures where the inner and sometimes the outer gears have broken during hard use of the engine be it on the road or on track or drag. Contrary to popular belief the wider nose crank which was introduced on BNR32 models from Feb 93 onwards and standard on BCNR33 and BNR34 models, while reducing the possibility to a degree did not eliminate the issue fully.Various attempts were made over the years to address the issues, Tomei, Jun, Greddy, HKS and Reimax (Japan) and Nitto (Australia) all made uprated pumps with bigger diameter and thicker pump gears to increase flow and overall strength which is much needed on track or on a high revving RB26 to ensure the engine has ample oil supply and durability. However they are based on the flat drive design.
Tomei oil pump with Supertec Spline Drive

Nissans own OEM pump (81mm outer pump gear) as supplied from the factory along with the N1 pump (77mm) utilise gears made from sintered metal which is weaker than billet steel equivalents. The Nismo pump is a steel version of the N1 with same flow and pressure. Reimax offers a billet steel gear upgrade kit for both OEM and N1 pumps, but upon testing we found clearances to be greater than stock N1, OEM and Nismo pumps, which in our view would increase potential failure.

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

Modifying the Oil Pump Housing

This is something that we were looking at recently. A pump doesn't like to do two things. It doesn't like to have to pickup, and push a fluid. It likes to do one thing. We think that some of the restriction to the inlet of an RB pump causes some issues. Check out these modifications done to a JUN pump. 

This video from Real Street Performance shows Jay go over how to take apart and inspect a 2JZ oil pump prior to installing it on an engine.  While an RB isn't a 2JZ, they both are similar style of pumps, and what goes for 2JZ generally goes for RB. 

Oil restrictor

Located in block. Limits the amount of oil that flows to the head. As the RB26
is solid lifter, it does not need as much oil up in the head as a hydraulic lifter RB25.

Stock 2.0mm
N1 1.2 mm (some of the newer N1 blocks seem to have a 2.0mm restrictor)
Tomei 1.5 mm

Oil Jet Squirter

The pistons in the RB26 have oil cooling channels in them. The oil squirters direct oil at the holes/channels in the pistons. Along with OEM, Reinik and Tomei both have oil cooling channel pistons.  

Oil Jet Squirter - 11560-05U10

Swinging oil pickup

  • Special Nismo part
  • Was used in the Super Taikyu spec motors
Swinging oil pickup in an RB26dett







    Oil pan baffle plates and modifications

    Stock RB26 oil pan. Front differential is on the right side.
      Its 2024 and guys like Robetro from Rav Performance have some great data and video of oil pressure logs on an RB26. This data is pretty scary, even on a stock car with stock pan. Add a modified car, and your oil pickup is probably seeing a lot of air on acceleration. 

    Did you watch the video? Are you going to add an extended sump? Are you thinking about an Accusump? 

    Extension on left side of the pan. This is a Nismo baffle plate

    Subaru owner removing RTV from an RB26 oilpan

    Extended sump on Australian GT-R

    Greddy Oil pan extension installed. I do not like that the oil drain bolt is the lowest thing on the car

    Greddy Oil pan extension installed. I do not like that the oil drain bolt is the lowest thing on the car

    Greddy Oil pan extension installed. I do not like that the oil drain bolt is the lowest thing on the car

    Oil Drainback

    Oil drainback for rear of RB26 head

    Some people modify their RB26 to return oil that accumulates at the back of the head directly back to the oil pan. Some will return to the oil drain, others to other places on the engine. You can buy an oil drainback here.


    The Accusump is an oil accumulator that stores a reserve of oil under pressure. Under conditions of a drop in oil pressure, the oil that is in the Accusump pressurizes the oiling system. Once the oil pressure comes back up, the Accusump
     fills back up


    Cam Cover

    The cam covers, or valve covers in an RB26 have breathers at the back of the engine.  An RB26 moves a lot of aerated oil around in the engine and though the top of the engine. An oil catch can, and baffled breathers are important to prevent oil contaminating the intake air.

    Stock valve cover baffling at the top. Nismo N1 baffling at the bottom.

    Camshaft splash plates from Boostdoc

    R34 N1 Super Taikyu catchcan setup

    Oily air sucked and burned in the engine, lowers the effective octane of fuel. It also coats the inside of the inlet manifold, intercooler piping,etc, and can end up with deposits on the valves. So, what happens if you just take all that "junk" off, and just put a breather on? Well under vacuum, air will enter the engine through the breather.  No big deal. No problems normally.  However under boost, air from inside the engine, will try and move out of the engine.  This would be no problem if it were just air, but its not.  It has oil suspended in the air. So even with a breather filter on the engine, you will have oily air come out the breather.  This oily air will get all over your engine compartment. For one it creates a big mess. For two it is flammable.

    Read more:

    Dry Sump

    Why do you need dry sump? If you have to ask that question, then you probably don't need it. It is seriously for the 2% of people out there that exceed the capacity of their oiling systems. They are expensive, complicated, and belt driven. However they are the most positive way to insure you have oil pressure at all times. There is a reason that all serious race engines use some kind of dry sump to ensure oil pressure. 

     Imagine an engine. Imagine G-forces. 1 G is the force of gravity. Many cars can accelerate with more than 1 G. Laterally we can see over 1 G. Braking we can see more than 1 G.  Oil is the fluid that cools and protects components in the engine. It carrys away the bad stuff (dirt, debris), and is a non compressible fluid between the rotating and stationary parts of the engine. In the case of a rod bearing its rotating and reciprocating, but you get the idea.  At 1 G, laterally, imagine standing the engine on its side. Where does all the oil in the pan go? It all goes to the opposite side. Now if you are turning big RPM, and the oil pump is sucking up as much oil as it can, what happens when it sucks air? At some point it runs out of oil in the pan. This air, supplied to the oiling system is compressible. Things happen like the bearings and rotating equipment comes into contact. If this happens enough, we spin a bearing. Heat turns the spun bearing into mush. Spin it long enough and that same heat weakens a part, and if you are unlucky enough, it ends up looking like the engine at the top of this post. 

    A dry sump setup actively scavenges oil from the engine. So not only is it picking up from the pan, it is pulling oil from certain sections of the engine. It takes this oil that is scavenged and puts it in a oil tank. The oil tank helps to separate any air from the oil and then maintains a positive head of oil on the supply side of the dry sump pump. Air is the enemy in the oil system. Keep it out, your bearings will thank you for it.  Dry sump isn't for everyone. However if you are big into circuit, or drag racing, I highly recommend it. If you can't afford to do it right once, then you certainly can't afford to do it twice. 

    Dry sump on a street car R32 GT-R
    Dry sump pump

    Ross Dry Sump

    Ross dry sump pump. Also visible is their damper with crank trigger. 
    Four Stage Dry Sump pump. 1.5" Pressure. 3 x 1.75" Scavenge with integral regulator. RB25/26/30 configuration
    More information on the Ross dry sump kit
    Modified RB26 oil pan. 4 stage dry sump pump. Pulley and Belt. Bracket. Cam trigger, Crank trigger

    Some more dry sump pans

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