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Rb26 Rod Bearing Clearances

Blue32

By Blue32,
in Engines & Forced Induction

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Blue32 Experienced

Blue32

Posted
Posted

After rebuilding my RB26 with the following specs I have spun a bearing on no 2 after 2000kms. All of the other bearings are also hammered - and I believe it may be due to a clearance issue.

Here are the specs:

Aries Pistons and rings (86.5mm)

std rods with ARP bolts

ACL Race series bearings

STD oil pump (start the flaming....) oil pressure = 20psi hot at idle up to 80psi odd at high revs (ie good oil pressure)

Trust baffled sump (insert type, not weld on)

Castrol 10W60 edge syn oil

2xoil coolers

external filter block

Tomei head oil restrictor

The engine ran strongly and made good power (high 300rwkws), the knock recorded (pwr fc) was always <35, AFR always logged and spot on via laptop and wideband.

They should be the related specs required - please ask if you require more info.

My engine was built with around 2.5 thou clearance on the rod bearings, although the factory spec as per the manual is 0.8 - 1.5 thou. I am wondering if the greater clearance of 2.5 thou has killed the bearings and what clearances people are using in similar built motors of the same horsepower.

I am looking for ideas from people with EXPERIENCE / and or ENGINE BUILDERS of 400rwkw RB26 engines here - please don't post if you don't know what you are on about!!

Any help is greatly appreciated, I really don't want this to happen again!!!!

Cheers,

Andrew

Blue32

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MYRB30 Rising Star

MYRB30

Posted
Posted

Mines no fire breather, but my big ends were set around 1-1.5 thou and the mains I set at 1 thou. I was bit worried that the mains could have been tight, but it was with in spec. I have since completed 30,000km plus.

My Vl turbo done some 100,000km and I set the mains closer to 2 thou and the mains similar I think.....

My first imression was that 2.5 thou sounds rather loose for an RB engine. Remember that NIZPRO run what are considered to be tight clearences, like 1-1.5 for both mains and big ends...

Other than contaminated oil (or surge), detonation and clearence issues bearings are generally issue free.

I totally sympathsize with you.

9krpm Mentor

9krpm

Posted
Posted (edited)

Andrew, you are fairly fast at Mallala and your engine failed at the track. Have you consider other causes especially oil surge with your setup?

What oil pump and oil cooler have you been using? What was your oil temperature when the engine failed?

With the amount of g force you are doing around Mallalla, the Trust baffle insert may not be enough if you have a high flow pump. I think a Trust sump extension kit will help your oil surge

Edited by 9krpm
unique1 Mentor

unique1

Posted
Posted (edited)

i run 2 thou on a 420rwkw rb26, has made over 450rwkw on dyno and no dramas with bearings. Im using acl race series if that matters. Has been running for 8 months with no problems. I got this clearance reccomended to me by a well known rb26 specialist workshop so i trust them 100%

Edited by unique1
Blue32 Experienced

Blue32

Posted
  • Author
Posted
i run 2 thou on a 420rwkw rb26, has made over 450rwkw on dyno and no dramas with bearings. Im using acl race series if that matters. Has been running for 8 months with no problems. I got this clearance reccomended to me by a well known rb26 specialist workshop so i trust them 100%

What oil pump are you running? I am starting to believe I may have had an oil delivery problem.......as well as the large clearances

BezerkR32 Veteran

BezerkR32

Posted
Posted

your clearances are not the problem, but your machine shop should have advised you on what to run. usually run larger clearance when revving engine harder, i agree that you might have starved it. also Castrol WTF. how did you measure these bearing clearances?

What oil pump are you running? I am starting to believe I may have had an oil delivery problem.......as well as the large clearances
unique1 Mentor

unique1

Posted
Posted (edited)
What oil pump are you running? I am starting to believe I may have had an oil delivery problem.......as well as the large clearances

jun high volume oil pump, gets around 27psi at idle and 80psi or so at full rpm when warm, i rev to 8500rpm usually. I also run the same oil as well (castrol edge 10w60)

Edited by unique1

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