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Discussion Starter #1
Hello,

My car is a 1990 BNR32 (will have new forged internals, new r34 crank, n1 oil pump, GT2860-5 turbos, etc....)

I did quite a bit of searching on this forum. I've decided for my rebuild to go with the N1 Oil Pump, my bottom end will be completely balanced/blueprinted. After all my research it seems people only have issues with the N1 when they don't balance, when they bounce off the rev limter, and/or rev passed 8500rpm.

I was wondering for street car that will see around 10 lapping days a year, what oil restrictor for the head should I put (tomei is 1.2mm), also what should size should I drill the oil return in the head (should I drain all the returns?) and lastly do I need a head drain mod (a drain at the back of the head to the oil pan)? Also I believe that the front oil feed is already block from the factory but some people say to block it, can someone clarify?

Thanks
Mitch
 

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Hi there...
There is only 1 oil feed to the head on a GTR, there are 3 on a RB25 lump as fitted to the GTS... Put the 1.2mm Tomei oil restrictor in the block, extend the standard sump, fit an oil cooler. You can fit the external oil return from the head, I have fitted these before, not sure how much good they do though, but I guess it can't hurt!!! I would recommend a harmonic balancer for use with the N1 pump too...
 

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Discussion Starter #3
Thanks for reply.

I was planning on a ATi Harmonic Damper, its cheap insurance. So you wouldn't put a external head drain? and you wouldn't drill out the oil returns?
 

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Discussion Starter #5 (Edited)
You weren't joking, a nice read! I read pretty much all the pages, read quickly, no one has a definate answer what to drill the oil returns out to. Also some people do certain things and others don't. I feel the optimum setup, after reading that massive thread, is to put a 1.5mm restrictor in the head, put an external drain back from the head (some people just dremel the stock rear drain and make it bigger), drill out oil returns, overfill oil when at the track, and an aftermarket sump baffle (or extenended sump). Does anyone have a clue at what size to drill the oil returns?
 

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To add more confusion my R33 GTR in totally stock form engine wise, at 1 bar, did countless *very* hard driven track days for over a year, with zero oiling issues, I just overfilled the sump to 10 mm over the full line. My new engine has extended sump, Tomei oil pump, external drain and 1.2 mm head oiling restrictor. I intend to set the hot oil pressure to something well under 100 PSI though, which is trivial with the Tomei pump as the pressure relief valve is external. My personal take is too much oil staying in the cam boxes is due to excessive piston blow by, and the head "drain" usually works by acting more as an additional sump breather. I intend doing some flow and pressure differential checks at some stage. There are as many opinions on this as there are asylum seekers in MK though.
 

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yep two feeds...
How can it be 2 feeds into the head if one feed in the block is blocked off or are you just being difficult? :D

A RB25 has 2 feeds, both with restrictors.

A RB26 has just one feed going into the head as the second is blocked off.

Rob
 
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true but it should also help to keep more oil in the bottom of the pan wouldnt it
To a point yes. Out of the cranks vaccuum, but not the head.

However, controlling windage is a good thing. Its only really worthwhile if you can get the one with the teflon scraper that virtually touches the crank. Maximum effect.

You really need a crankcase breather...
 

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I belive a crankcase breather is a god send.

Even when an oil cooler is fitted
It helps keep oil temps down especially in high altitude and high humidity.
As the engine needs to breathe.
 
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