Rb30 Pressurising Sump...

[cactus]

Hey guys,

Hoping someone might have some advice.

I have an RB30/25, series 2 block with a series 2 RB25 head (turbo). head is standard with poncams, motor is built with 8.9:1 comp ratio, 20 though bored and thats about it. I havent installed oil restirctors or anything like that. Have good oil pressure, good compression, and motor is strong. One issue I have though, is the motor seems to be pressurising the sump. I can't work out why...

A lot of the time it has blow oil out the side of the sump under full load. Not sure what info anyone needs, but any ideas as to what it could be and how to fix would be greatly appreciated.

Cheers,

Matt.

[Duncan]

how have you set up the cam cover breathers?

[MBS206]

What do you mean out the side of the sump?

[cactus]

What do you mean out the side of the sump?

Sorry, wrote that in a rush yesterday... blows the seal between the block and the gasket and starts shooting oil from there.

Bigger breathers on the cam covers, with 18mm lines to a catch can which has a decent filter on top. This reduced the amount of pressure, but still having issues.

[toddlls]

Dont know whether this would work but what about putting a pressure relief valve in sump that circles back to a sep catch can-just a thought

[Bliksem]

Suprised its not blowing the dipstick out first... Sounds like excessive blow-by to me... have you done a leakdown test?

Edited August 31, 2010 by MintR33

[r33_racer]

what was your piston to bore clearance and ring end gaps?

[James_03]

Do your comp test again and tell us what it gets per cylinder.

Can't possibly have good comp with that much blow by, unless something like the vvt drain has been plumbed into the inlet or something.

[cactus]

Do your comp test again and tell us what it gets per cylinder.

Can't possibly have good comp with that much blow by, unless something like the vvt drain has been plumbed into the inlet or something.

Wouldn't have a clue what the clearances are, I didn't build the motor. If it was blow by, wouldn't there be heaps of smoke coming from exhaust as a result of oil burning where it should'nt be? Dipstick is fine, its just the sump-block thats having issues. Motor is in good nick, recently had the head off (while installing cams I made a boo boo), and bores were fine. Pistons do have a lot of play, but apparently they (according to setting provided with pistons, being CP make) require this...

Will do a comp test, but motor is very strong. Doesn't blow much oil at all/doesnt use any oil, until it starts squirting out the side lol.

VVT/head drain T's into turbo oil return.

[Duncan]

It's RWD right? no 4wd sump adapter?

I can only guess it's not caused by blowby if compression is good and there is plenty of breathing. Possibly only happens when the motor is running because when it stops the oil drains back to the sump below the leak?

Pull the sump off and make sure both surfaces are flat, and well sealed with gasket goop.