Jump to content
SAU Community

Recommended Posts

Circuit, drag or drift RB’s with excess oil in the cylinder head, not enough oil in the sump, oil in the catch can, wet sump, oil surge, lack of oil, big end bearing failure etc

I get about 10 X PM’s a week from guys with this problem, I have posted up what is required many, many times. But still the guys want a solution after they have assembled the engine, it is in the car and they now have a problem. Well the bad news is there isn’t one solution. The answer is to do all of the steps when you are assembling the engine and then you won’t have a problem. There is no one magic, off the shelf solution. Buying a brand name restrictor, sticking it in the block and expecting that to fix the problem on its own is naive at best. Similarly fitting a baffle in the cam covers may overcome the catch can problem but it will still leave the others. :P

On the circuit race cars we take a 5 step approach in controlling the amount of oil that is trapped in the cylinder head and/or blown into the catch can; :D

1.Block off one oil feed in the block (RB26’s have this standard)

2.Fit an appropriately sized restrictor to the other feed. The size of the oil pump is one of the determinates for the size of the restrictor, ie; a high flow, high pressure pump needs a smaller restrictor. Constant higher RPM needs a smaller restrictor etc.

3. Fit an external oil return from the rear of the cylinder head to the sump

4. Drill out the oil return galleries in the head and block

5. Machine around the oil return galleries to facilitate access for the oil

It seems to me that many guys do #2, and some maybe #1. If you haven’t done #3, #4 or #5, then please remember that they are cylinder head off jobs. Drill out the oil return galleries in the head and block is pretty much self explanatory. As is machining (die grinder) around the oil return galleries to facilitate access for the oil to the return bgalleries. The external oil return fits to the rear of the cylinder head at the Y, there is a welsh plug there that you can remove and replace with a fitting. Then braided line to another fitting in the top of the LHS sump wing if you have one. If you don't, then you should for circuit and drift work.

I have tried to include every commonly used word that I can so that this post pops up when a search is done on this problem. Maybe that will cut down the PM's to only 5 a week :(

:D cheers :D

PS; this post is not designed to stop people asking questions via PM's, maybe just reduce the repetitive ones. Plus it will hopefully save people a lot of money pulling the cylinder head off to do what is easily done for very $few when the engine is being built in the first place.

Edited by Sydneykid
  • Like 2
Sk in your experience do RB20's and 25's suffer this problem as much as RB26's? or is it more related to the greater grip and g's that a GTR creates causing the problem? or is there a design issue across the whole RB range?

Yep, it's all RB's, the block, oil feed and return systems were designed for ~6,000 rpm occasionally. Circuit, drift and drag means higher than that rpm and for longer periods of time.

:P cheers :)

  • Like 1
For the oil return on an rb26, can you add a fitting to the standard sump or does it need to be a custom sump? Thanx

If you are maintaining sustained high rpm for long periods (such that it affects the oil return) then I would respectfully suggest that a sump upgrade is necessary.

So to answer the question, yes you can. Since the crank turns clockwise (looking from the front) plumbing the oil return into the top LHS of the sump would be logical. That way it is feeding into the partial vacuum created by the crank spinning.

:dry: cheers :)

Edited by Sydneykid
  • Like 1
Craved - you can't miss it if you are looking at the back of your head... so to speak. :)

hahahah ok :dry:

i had a look at the head before i left for work .. there are 2 welsh plugs there.. both rather large..

any details on the process of getting a fitting in there? sizes?

look like about an inch i diameter for the top one, and slightly larger for the bottom one..

do you tap into,braze on a fitting to the welsh plug or run something the full size?

Thanks SK.

I've had my blocks head oil return honed to improve oil flow however the actual head hasn't been played with.

My heads being pulled off next uni holidays, I will then drop in one 2mm restrictor and block the other.

I'm still a little concerned blocking off one restrictor with a hydraulic head being predominately street driven.

Thanks SK.

I've had my blocks head oil return honed to improve oil flow however the actual head hasn't been played with.

I'm still a little concerned blocking off one restrictor with a hydraulic head being predominately street driven.

yeah same, thats why i was thinking the 1.5mm x 2 with the extra return line in the back of the head...

i'll be getting the head and block returns "matched" the help as wells as a hone on the block feeds.

Do remember Craved that you have an extra oil feed from the VCT were as I don't.

I would feel perfectly safe running an R33 VCT head with only one block oil restrictor. As essentially the head is then receiving oil from 1 x 2 mm and 1 x 1.2mm oil feeds.

The R32 RB25DE head on the other hand doesn't have a vct oil feed.

I ran running 1 feed by my head bloke (Chris Milton Engineering) he was concerned with the hydraulic head receiving oil from 1 feed.

He said on a prior rb30det they did ran a vct r33 head they left the rb30's standard 1.8mm restrictor in place, blocked off one and obviously ran the vct feed supply. It was fine.

I didn't have my motor built by Milton Engineering as they wanted too much.. I almost fell out of my chair... Only the head was rebuilt as they had previously had experience with them.

In a round about way I am asking Gary if he has ran an R32 RB25DE head with only one oil feed for a duration of time without experiencing issues.

Gary has mentioned the R33 head but not the R32 head.

was my understanding that the VCT feed didn't lubricate the head, only pressurised the inlet cam VCT unit, then drained directly back down and not out in the head to feed the lifters and lubricate the cams etc... i could be wrong of course.

I don't know if the vct feeds the lifters with oil pressure, the only real way to tell would be to some how trace the oil galleys in the head.

I'll be doing this with my r32 head, I'd assume both oil feeds are joined and not seperate.. For example not joined oil galleys: rear oil feed supplys the rear cam bearings and lifters, front oil feed supplys the front cam bearings and lifters.

Do remember Craved that you have an extra oil feed from the VCT were as I don't.

I would feel perfectly safe running an R33 VCT head with only one block oil restrictor. As essentially the head is then receiving oil from 1 x 2 mm and 1 x 1.2mm oil feeds.

The R32 RB25DE head on the other hand doesn't have a vct oil feed.

I ran running 1 feed by my head bloke (Chris Milton Engineering) he was concerned with the hydraulic head receiving oil from 1 feed.

He said on a prior rb30det they did ran a vct r33 head they left the rb30's standard 1.8mm restrictor in place, blocked off one and obviously ran the vct feed supply. It was fine.

I didn't have my motor built by Milton Engineering as they wanted too much.. I almost fell out of my chair... Only the head was rebuilt as they had previously had experience with them.

In a round about way I am asking Gary if he has ran an R32 RB25DE head with only one oil feed for a duration of time without experiencing issues.

Gary has mentioned the R33 head but not the R32 head.

The R32 RB25DE cylinder head requires oil flow the same as an RB20DET cylinder head. The questions are still the oil pump flow and pressure, the rpm commonly used and the length of continuous time that rpm is used. Plus what work has been done on the oil return system. So it’s not a simple one size answer, it’s more a 3 dimensional table. If I have time I will make up a rule of thumb table and post it in this thread.

:laugh: cheers :P

The R32 RB25DE cylinder head requires oil flow the same as an RB20DET cylinder head. The questions are still the oil pump flow and pressure, the rpm commonly used and the length of continuous time that rpm is used. Plus what work has been done on the oil return system. So it’s not a simple one size answer, it’s more a 3 dimensional table. If I have time I will make up a rule of thumb table and post it in this thread.

:) cheers :D

]

A table would be GREAT, go Gary.

  • 2 weeks later...

regarding restrictors and such, what kind of restrictors should one use on a rb20 using a n1 oil pump?

also ive a shot the back of my head and not sure where i should fit the external drain, advice on both q's is always appreciated.

post-9364-1144374319.jpg

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now



  • Similar Content

  • Latest Posts

    • The average previous owner for these cars were basically S-chassis owners in the US. Teenagers or teenager-adjacent. I often tell people that neglect is easier to fix than something that was actively "repaired" by previous owners.
    • Update 3: Hi all It's been a while. Quite a lot of things happened in the meantime, among other things the car is (almost) back together and ready to be started again. Things that I fixed or changed: Full turbo removal, fitting back the OEM turbo oil hardlines. Had to do quite a bit of research and parts shopping to get every last piece that I need and make it work with the GT2860 turbos, but it does work and is not hard to do. Proves that the previous owner(s) just did not want to. While I was there I set the preload for the wastegates to 0,9bar to hopefully make it easier for the tuner to hit the 370hp I need for the legal inspections that will follow later on. Boost can always go up if necessary. Fitted a AN10 line from the catch can to the intake hose to make the catchcan and hopefully the cam covers a slight vacuum to have less restrictive oil returns from the head and not have mud build up as harshly in the lines and catch can. Removed the entire front interior just shy of the dashboard itself to clean up some of the absolutely horrendous wiring, (hopefully) fix the bumpy tacho and put in LED bulbs while I was there. Also put in bulbs where there was none before, like the airbag one. I also used that chance to remove the LED rpm gauge on the steering column, which was also wired in absolute horror show fashion. Moved the 4in1 Prosport gauge from sitting in front of the OEM oil pressure gauge to the center console vents, I used a 3D printed vent piece to hold that gauge there. The HKB steering wheel boss was likely on incorrectly as I sometimes noticed the indicator reset being uneven for left vs. right. In the meantime also installed an airbag delete resistor, as one should. Installed Cube Speed premium short shifter. Feels pretty nice, hope it'll work great too when I actually get to drive. Also put on a fancy Dragon Ball shift knob, cause why not. My buddy was kind enough to weld the rust hole in the back, it was basically rusted through in the lowermost corner of the passenger side trunk area where the wheel arch, trunk panel and rear quarter all meet. Obviously there is still a lot of crustiness in various areas but as long as it's not rusted out I'll just treat and isolate the corrosion and pretend it's not there. Also had to put down a new ground wire for the rear subframe as the original one was BARELY there. Probably a bit controversial depending on who you ask about this... but I ended up just covering the crack in the side of the engine block, the one above the oil feed, with JB Weld. I used a generous amount and roughed up the whole area with a Dremel before, so I hope this will hold the coolant where it should be for the foreseeable future. Did a cam cover gasket job as the half moons were a bit leaky, and there too one could see the people who worked on this car before me were absolute tools. The same half moons were probably used like 3 times without even cleaning the old RTV off. Dremeled out the inside of the flange where the turbine housing mates onto the exhaust manifolds so the diameter matches, as the OEM exhaust manifolds are even narrower than the turbine housings as we all know. Even if this doesn't do much, I had them out anyways, so can't harm. Ideally one would port-match both the turbo and the manifold to the gasket size but I really didn't feel up to disassembling the turbine housings. Wrapped turbo outlet dumps in heat wrap band. Will do the frontpipe again as well as now the oil leak which promted me to tear apart half the engine in the first place is hopefully fixed. Fitted an ATI super damper to get rid of the worn old harmonic balancer. Surely one of the easiest and most worth to do mods. But torquing that ARP bolt to spec was a bitch without being able to lock the flywheel. Did some minor adjustments in the ECU tables to change some things I didn't like, like the launch control that was ALWAYS active. Treated rusty spots and surface corrosion on places I could get to and on many spots under the car, not pretty or ideal but good enough for now. Removed the N1 rear spats and the carbon surrounding for the tailpipe to put them back on with new adhesive as the old one was lifting in many spots, not pretty. Took out the passenger rear lamp housing... what do you know. Amateur work screwed me again here as they were glued in hard and removing it took a lot of force, so I broke one of the housing bolts off. And when removing the adhesive from the chassis the paint came right off too. Thankfully all the damaged area won't be visible later, but whoever did the very limited bodywork on this car needs to have their limbs chopped off piece by piece.   Quite a list if I do say so myself, but a lot of time was spent just discovering new shit that is wrong with the car and finding a solution or parts to fix it. My last problem that I now have the headache of dealing with is that the exhaust studs on the turbo outlets are M10x1.25 threaded, but the previous owner already put on regular M10 nuts so the threads are... weird. I only found this out the hard way. So now I will just try if I can in any way fit the front pipe regardless, if not I'll have to redo the studs with the turbos installed. Lesson learned for the future: Redo ALL studs you put your hands on, especially if they are old and the previous owners were inept maniacs. Thanks for reading if you did, will update when the engine runs again. Hope nothing breaks or leaks and I can do a test drive.
    • No those pads are DBA too  but they have colors too. I look at the and imo the green "street" are the best.
    • I’m not sure what happened I told them about sonic tunes free OTS tune and the next the I know .. I was booted..   To funny 
×
×
  • Create New...