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Head To Sump Oil Flow?

700HP-GTR33

By 700HP-GTR33,
in Engines & Forced Induction

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700HP-GTR33 Mentor

700HP-GTR33

Posted
Posted

Hello all,

Re-build in progress...RB26.

Tomie restrictor(1.5mm) on the way...thanks Sean :(

Not looking for a sump extension but more of a modification.

This has been a discussed topic but not much information on hear for my liking.

It reducess pressure thus creating less blow-by

and helps maintain a good level of oil in the sump which at high revs can be low causing problems

Has anyone drilled the head and sump to improve the flow of oil?

If so, what size oil return lines did you use?

Where is the best location and height to tap into the head?

Where would it be best to return the line into the sump?

Pictures would be great if anyone has them.

Also am unsure if this mod is good for any other RB Motor.....sure it would not hurt.

;)

Thanks

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R31Nismoid Grand Master

R31Nismoid

Posted
Posted

People have gone external oil drain (plenty of threads/pics about it now)

IMO, as long as the restrictor is fitted, for a street car you wont ever have a problem.

You only would really need a external drain if you ran a super volume pump (JUN etc) but even then, plenty of people that dont have external drains and running without issue where restrictors are properly used etc etc...

You don't actually 'drill the sump' in those words, the sump is where the oil ends up.

If you mean boring out the sump... thats a waste of money.

700HP-GTR33 Mentor

700HP-GTR33

Posted
  • Author
Posted

Ok,

So if you have a Jun,Tomei high flow oil pump fitted then this is a must.

You would then consider an extended sump.

I would think though this would be an great alternative for cars with a lot of blow-by

and hitting the rev limiter often with out the restrictor in place or extended sump.

Especially if they don't want to remove the head to fit a restrictor.

Tapping a 10mm hole into the sump and threading it would be an easy job to do.Or am I mistaken?

It may not even need to be 10mm...this is why I ask...it could be 5mm....or even 4,3.

R31Nismoid Grand Master

R31Nismoid

Posted
Posted
Ok,

So if you have a Jun,Tomei high flow oil pump fitted then this is a must.

no... it could be considered. I wouldnt say a must at all being there are PLENTY of cars without external drains with high volume pumps (they would have restrictors and so on)

There aren't many that use it.

Adriano Grand Master

Adriano

Posted
Posted

You can drill the stock oil returns from 8mm to 9.5mm (3/8 inch) with a long drill bit. Also drill out the 5 holes in the sump that go from the back of the sump section to the main area from about 1mm to about 4mm. Lastly you can fit an external return to the back of the head. Another idea which i will soon be investigating is a breather in the crankcase, to remove the blowby that prevents the oiol travelling down the drains.

msnismo Grand Master

msnismo

Posted
Posted

o i see. yes, you drill out the tiny little 2mm holes in the sump, (where the driveshaft tube runs over) to 8mm or as big as you can go.

also a oil return is a must, even standard pumps will still fill the rockers up. ideally a -12 (16mm) or bigger is best for the oil return from the head. just making it as compact as you can is the hard bit given the clearance at the rear of the head.

dave here. (to4gtr)

700HP-GTR33 Mentor

700HP-GTR33

Posted
  • Author
Posted
You can drill the stock oil returns from 8mm to 9.5mm (3/8 inch) with a long drill bit. Also drill out the 5 holes in the sump that go from the back of the sump section to the main area from about 1mm to about 4mm. Lastly you can fit an external return to the back of the head. Another idea which i will soon be investigating is a breather in the crankcase, to remove the blowby that prevents the oiol travelling down the drains.

Drilling the stock oil return makes a lot of sense, 9.5mm would be an added improvement but

what is the most they can be drilled out. Dave though has suggested these can be drilled out to 12mm.

How far can you go?

The drilling out the 1mm holes is suggested by Tomei when fitting their

oil baffle plate they though suggest 6mm. Dave has gone one better and has suggested 8mm.

How far can you go?

I believe maybe with the stock returns drilled out to 12mm, Sump return oil gallery 1mm drilled out to 8mm

combined with a Tomei 1.5mm oil restrictor may just work when the engine is out.

It would be great to have though a quick fix solution to this problem with an extra return line, maybe

picking up oil 3/4 of the way up the head 10 to 12mm line returning back into maybe 1/2 way up the sump.

Experimenting with the idea that we could vent this also to our existing catch can may lower bottom end pressure

which always ends up blowing your dip stick out on a dyno run.... :) .That is if you haven't tide it up.

Anyway, I hope this helps others

700HP-GTR33 Mentor

700HP-GTR33

Posted
  • Author
Posted
What does your engine builder have to say about it all?

Have they even built RB's before?

Yes my engine builder has built many RB26 motors.

This thread is to help myself and others make decisions on

approaching RB Oil control issues.

I now have a better understanding and knowledge after posting this thread.

It will add to the great data base on here. :cool:

700HP-GTR33 Mentor

700HP-GTR33

Posted
  • Author
Posted

In my application I have decided to keep my N1 oil pump.

Fit a Tomei restrictor,1.5mm.

Drill out the sump holes(5) from 1 to 6mm and

increase the oil line return size to 10mm.

No sump extension..not needed..add 1 litre more oil if going on track/drag.

I will not be hitting the rev. limiter much (Set it to around 8K using all forged bottom end)as it is a road car which hardly gets track or drag use.

R31Nismoid Grand Master

R31Nismoid

Posted
Posted
Yes my engine builder has built many RB26 motors.

This thread is to help myself and others make decisions on

approaching RB Oil control issues.

I now have a better understanding and knowledge after posting this thread.

It will add to the great data base on here. :(

We already have such a thread, and its been around for quite some time (As linked in the FI Guide)

http://www.skylinesaustralia.com/forums/Oi...ui-t110680.html

So if thats all this thread kinda serves... Then we dont need two threads on the same thing

Cheers

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