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Rb26 / 30 Knocking Sound W/ No Load, Big End Bearing? [Vid]

ST240

By ST240,
in Engines & Forced Induction

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ST240 Enthusiast

ST240

Posted
Posted (edited)

The oil light came on idling at a red light the other night after some hard pulls, however my pressure gauge did not show a loss in pressure when the light was on (what causes the oil light to come on? Is it strictly a pressure loss? I later tinkered with the plug and it may or may not have been loose). I was a few blocks away from the house and I noticed this noise.

The sound in the video only shows up at around 2500 RPM briefly. It also doesn't seem to really be there when the engine is cold. Tomorrow I will cut apart the oil filter to see if I can find bearing flakes.

I'm really scratching my head as to what that noise could be. Almost sounds too rapid to be a big end bearing. But the fact that it's not there when it's cold is a little unsettling. I've also read on lots of RB forums guys think the sound is coming from the head, which this one does, and it ends up being a big end bearing. Any ideas?

Funny how I bagged the living shit out of this engine all summer last year and the first few hard pulls this year she gives me problems.

Edited by ST240
GTScotT Grand Master

GTScotT

Posted
Posted

Funny how I bagged the living shit out of this engine all summer last year and the first few hard pulls this year she gives me problems.

Thats a common thing to me, lots of cases i know where a motor has been dormant for a while and then restarted without fresh oil and its given way. I think the old oil dries up and causes things to seize (like lifters) or oil starve to things like rod bearings.

I havent heard the vid yet as im at work, thus cant comment on that im sorry.

AngryRB Grand Master

AngryRB

Posted
Posted

get a piece of pipe and put your ear to it and test where the noise is,

could it possibly be a worn bearing in one of the pullies? i have this noise on a falcon ute but its constant , pretty sure its a bearing noise from worn pully.

kitto Mentor

kitto

Posted
Posted

Yeah, sounds like one of the rod bearings has just started to spin, but it doesn't sound overly bad.

I'd pull the motor out, rip the sump off, inspect all the bearings and crank. You never know you might get away with just replacing the shells if you havn't scored the crank.

ST240 Enthusiast

ST240

Posted
  • Author
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Pulled it apart tonight. I immediately knew what happened when the bearings were clamped on the journals.

SDC11370.JPG

Nothing a ballpeen can't straighten out.

SDC11371.JPG

Hey guys, it's ok if my bearing shells look like bacon, right?

SDC11372.JPG

At least the journals look ok.

Yep. She starved of oil :(. I think I remember the corner that did it in actually, a sharp U-turn at about 7k. Lucky it was on the street and not a track where I may not have noticed it. I also forgot to overfill the sump. f**k! Damn RBs and their starvation issues. A few more hard pulls and it might have been a different story.

This is how THREE of the six big ends looked lol. But at least the journals look half decent and can be reground. But in the spirit of this build I may even gamble and just polish them up, new shells, and slapper back together. Experienced guys, what do you think?

  • 5 weeks later...
ST240 Enthusiast

ST240

Posted
  • Author
Posted

Ok so I rebuilt this thing. And the exact same timeframe, its f**king knocking again.

What the hell could be starving my bottom end of oil so consistantly? Am I missing something!? I've only driven it hard a few times and I've kept the revs down. Theres also 6L in the sump.

What the hell could be causing this???

R33-RB26DETT Proficient

R33-RB26DETT

Posted
Posted

when you rebuilt it did you add an oil restrictor to the head?

Also did you add an external oil head to sump drain?

Both of these mods will help to ensure that oil isn't kept just in the head and that your bottom end isn't starved.

Rolls Grand Master

Rolls

Posted
Posted (edited)

Did you personally build it yourself or get someone to do it? Did you measure all of your clearances or did you just slap it together?

100% it is oil starvation? same bearings gone as before? could there be a blockage?

Edited by Rolls
ST240 Enthusiast

ST240

Posted
  • Author
Posted (edited)

I have the rear feed blocked and the front restricted down to 1.5 mm. No head drain though... I didn't even have the restrictors before I swapped heads.

Yes I did build it myself. And I did check the clearances. They all within, barely, but still in spec. I've built this engine before and I raced it two seasons with the RB25DE head without an issue. I didnt change anything on the bottom end and I it somehow died right after I put the RB26 head and new manifold on it. The reason I think it's starvation is almost all the big ends were cooked to varying degrees, and the mains were starting to go too. But maybe it isn't starvation.

Someone on another forum is suggesting if the crank isn't straight it can do this. Surely it would have to be knocking quite badly to wreck the bearings this fast?? I do have one of those special bosch sensors that I can listen with, but I havent recently. I'm only running 16* at 8.3:1. I maybe have driven 100 km on it, and had only a handful of hard single gear pulls.

Edited by ST240

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