Jump to content
SAU Community
  • Welcome to SAU Community

    Welcome to SAU Community, like most online communities you must register to view or post in our community, but don't worry this is a simple free process that requires minimal information for you to signup. Be apart of SAU Community by signing in or creating an account.

    • Start new topics and reply to others
    • Subscribe to topics and forums to get email updates
    • Get your own profile page, build reputation and make new friends
    • Send personal messages to other members.
    • See fewer ads!

    Consider joining our newsletter for the latest content updates

    Click here to register


Rb30 Gurus, Need Help! Lots Of Oil!

Recommended Posts

Hey everyone. I know theres a lot of info on this site but im having a hard timing finding some solid answers to my issue. and i figured i would also take this time to show off some of my build i have been working on this winter. Heres a rundown and whats happeneing.

This motor has been properly broken in, runs beautifuly, and pulls like a bat out of hell. With that said though i think theres some oiling issue going on. I attended a drift event last weekend and after some high rpm beatings i noticed my catch can being full of oil. not blow by, but regular oil. on normal crusiing, and quick WOT pulls to the 7k rev limit i barely have any condensation or milkly blow by in the can.

i'll post some pictures of my setup and a list of what i used in this build to give everyone the info. But i think what my conclusions are telling me is that this motor is still being given too much oil and not draining properly.

setup includes.

rb30 block and crank

fully balanced rotating assembly with crank collar fix

Nismo N1 oil pump

acl bearings,

manley rods

cp 8.5-1 pistons

tomei 1.5mm oil restrictors in block

all ring gap was measured a million times, rings were oriented correctly.

RB25det head

stock hydro lifters

supertech head kit, springs, 1mm oversize valves, titanium retainers

tomei rb20 cams 260 8.8mm lift

tomei cam gears degreed to spec

cometic MLS headgasket

spool head drain located on back on head going into a tee fitting for the turbo oil drain -10 an line

relocated the stock rb25 front head drain to a welded on bung on oil pan


running a greddy oil filter sandwich plate with -10 an lines to a oil cooler.

oil catch can is two -8an lines running off stock rb25 cam cover holes to a can with breather filter on top.

i guess im just not sure if this pump is just too much? or my drains are not flowing correctly? this pump sees about a 30 psi at idle at 180 deg F oil temps, close to 100 psi at 5k. ive been consdering putting a RB25 pump back in, im just not sure where to go from here if anyone has any suggestions i am all ears! the motor ran so well but im afraid to put any absuse on it till this issue is cleared up. i figured with the restrictions and the rear head drain i wouldn't have any problem but like i said my oil catch can was almost full of straight oil after about 5 runs drifting. right now i am just running castrol gtx 5-30w conventional oil.

some pics of the setup so everyone can see


Link to post
Share on other sites

Your problem is excessive blow-by and its stopping the oil in the head from returning to the sump in a regular manner, both your crankcase internal vents and internal head drains are working as vents so the oil is being trapped in the head and then being blown out your cam covers lines into your catch can.

You want to put a breather line off the inlet side of your sump -12AN is a good size, above oil level and run it directly to your catch can. Your cam cover lines should be atleast -10AN.

  • Like 1
Link to post
Share on other sites

have you put the external oil feed into the front of the head? I have 1 1.3mm restrictor middle blocked VCT feed 1.5mm spool head drain in its own drain to the sump and a 9litre baffled sump. on the street it pumps no oil in the can and on the track it will pump 500ml for the day. next time I was thinking of going to 1mm or 1.2mm restrictor just for the track work it dose.


Link to post
Share on other sites

Seems you are in the US or Canada?

Is the Castrol GTX you refer to a full synthetic, or mineral base with synthetic fortifiers? Suggest a change in oil spec, use the mineral base oil, and go to a 10W60. I'd think the piston rings are not yet bedded properly (particularly if chrome rings are used), and it shows as blow-by when you flog it at an event. You just can't run the engine hard enough/long enough on the road for it to show up.

As per other posts, bigger vent lines to the can, and oil feed restrictors to the head somewhere around 1.3-1.5mm would be a great help.

The catch can looks a tad small, but change/modify it to take a second breather filter. If the cross-sectional area on the filter necks is larger than the breather lines from cam covers then you reduce tendency for a venturi effect that can drag oily vapours straight out through the filters.

Bottom line is change a few things and persevere.

Link to post
Share on other sites

two restrictors. 1.5mm

the oil is a conventional mineral base oil.

i will agree i think the catch can is too small. i will look into making a bigger one with dual breather vents.

no oil drains were drilled out.

im confused as to why the rb25 never had a problem with this, why does the rb25/30 have this issue?

Link to post
Share on other sites

Your rings on your cp pistons are not sealing as good as the oem ring set on the factory pistons when it was just a 25.

Link to post
Share on other sites

On my RB30 I run 2 x 1.0mm restrictors. The back of the head drain (I don't have one) does stuff all except perhaps pressurise the cam covers making things worse. I have two lines from the sump as the RB30 seems to whip up a storm in the sump. one line goes to the top of a catch can and the other to the bottom (acts as an oil return). I now get no oil out of the cam covers. I used to have the catch can venting to atmosphere but would get oil mist over the engine bay so now I vent the catch can to a second catch can (a proper oil/air seperator would be ideal) and vent that to my turbo inlet.

Link to post
Share on other sites

how did you guys go about adding a port to the engine block? i already welded one bung on the oil pan for the front head drain, is there a way to drill a hole in the block to add a breather? then run a line to the catch can? i checked compression cold today and it was 125 across all 6 im on 8.5 cr pistons

Link to post
Share on other sites

Took the engine out to put smaller restrictors in and at the same time took sump off and drilled and tapped two holes inlet side as high as possible for the breathers.

If I were you I would use the line you have going to the head and run it to a catch can instead. Those head "drains" are at best useless and at worst part of the problem.

Link to post
Share on other sites

I believe he means the std rb25 VCT drain at the front of the head on exhaust side.

You really need a bung welded on the inlet side of the sump as high as practically possible. I wouldnt drill a hole in the block itself.

Link to post
Share on other sites

Yup exactly. I have the exhaust side drain going to the sump. If you think that's useless ill just block that off and run 2 bungs on the other side of the sump and run both of them to the catch can breather and a drain. My one question though now is what about any actual blow by the can collects? Now it's just going to be mixed with the oil. Isn't that bad?

Link to post
Share on other sites

Leave that drain where it is. It's fine. Just put 1 x -12an weld on fitting on the inlet side of sump and hook that up to your catch can. This will give the excessive crankcase pressure an exit to atmosphere without carrying large sums of oil with it.

Link to post
Share on other sites

cant beleive nobody mentioned cam cover baffles. I just jamed steel whool wraped in a stockings in my factory cam baffles and helped a shit load. no more oil out the breathers just oily mist and water condensation from the E85 when cold. If thats too dodgey for you, buy rb26 cam covers and install some mines baffles. this is realy a last resort but it does help quite alot.

Link to post
Share on other sites

Say what?

What does the colour of the sump matter?

And the inlet side is the RHD driver's side of the engine....where the inlet plenum sits. Exhaust on the LHS.

Link to post
Share on other sites

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

  • Create New...