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.

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;
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

cheers

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.

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Can a mod sticky this? Or even start a sticky thread re: oils?

Oil is the most important thing - and the more people aware of this, the better


Thanks

it goes into the FI guide like most other good threads

ill do it tomoz

any chance that someone would have a pic of the rear of the cyl. head, so we can see where the welsh plug is that can be adapted for the extra return line.

thanks for all your help with everything sydneykid

we do appreciate all the hours you spend answering pm's

out of question r32 rb25de pump would require 1 oil feed blocked off and the other being a 2.0mm feed?

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?

Craved - you can't miss it if you are looking at the back of your head... so to speak.

*Sends SK a pm regarding oil control*

kidding, kidding..

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.

cheers

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.

cheers

hahahah ok

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.

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.

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

]

A table would be GREAT, go Gary.

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.