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Rod And Main Bearings Shrank

Tomei_Powered

By Tomei_Powered,
in Engines & Forced Induction

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Tomei_Powered Rising Star

Tomei_Powered

Posted
Posted

I had ACL bearings on my conrods and main bearings and it all shrank like an mm to 2mm from their actual size when

removed. Bearings can be taken off by just a slight touch instead of sliding them off with some force.

Practically the bearings were just floating.

What could be the cause of bearings shrinking?

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The Dan Grand Master

The Dan

Posted
Posted

The actual cause is heat.

But yes, you are right, lack of oil pressure is the most likely cause for the bearing to be damaged, thus causing the heat when it's grinding away at the crank.

Who built the engine? Or do you not want to say?

darren lewis Apprentice

darren lewis

Posted
Posted
I had ACL bearings on my conrods and main bearings and it all shrank like an mm to 2mm from their actual size when

removed. Bearings can be taken off by just a slight touch instead of sliding them off with some force.

Practically the bearings were just floating.

What could be the cause of bearings shrinking?

basically heat related, the shells are actually made to sqeeze into the tunnel from new . this is called the bearing crush. the shells have lost their crush from a few reasons, 1. detonation

2 lack of oil or starvation

3 clearance problem ,, caused from assembly ,machining etc etc.

if you post up a pic of the bearing surface i can tell you which is the cause..

tridentt150v Grand Master

tridentt150v

Posted
Posted

Is that through the white metal or is it just the light??? How many Km's, normally bearings with copper showing are big mileage and/or abuse or a failed oil pump/no oil in motor.

If its through the white metal, you have a serious oil supply issue.

darren lewis Apprentice

darren lewis

Posted
Posted
Pics

definately oil starvation guys. normal thing that happens is the top end fills with oil cant get back to the sump quick enough. do you have restrictors? do you have a drain from rear of head or a catch can with a drain back to the sump? check oil pump is not broken? what type of oil used? oil cooler?

Tomei_Powered Rising Star

Tomei_Powered

Posted
  • Author
Posted

Sory, its the camera flash.

Bearings ran close 3k mileage.

No restrictors. Problem is, i dont have a catch can.

Oil pump was JUN. Bought new. HKS oil cooler and Motul oils.

This is just crap!

I just wanna find out the cause of it. Least i know whats the problem now..

MrStabby Grand Master

MrStabby

Posted
Posted
Sory, its the camera flash.

Bearings ran close 3k mileage.

No restrictors. Problem is, i dont have a catch can.

Oil pump was JUN. Bought new. HKS oil cooler and Motul oils.

This is just crap!

I just wanna find out the cause of it. Least i know whats the problem now..

High volume oil pump could be the problem. The stock engine already has problems draining oil from the top end, and the high volume pump just shoves more up there and drains the sump more quickly than the stocker.... ouchy

tacker Mentor

tacker

Posted
Posted

I am not sure but i would say that you have had some very fine dirt / grit in your engine either from assembly or ingressed from a oil change.

I am no expert but with a lack of oil pressure you have metal on metal which causes heat and a dis coloring of the copper surface. From these pictures i cant see any real heat discoloring on the bearing. What i see is a good shiney finish which could be from fine particals slowly polishing your bearings away.

What leave me wondering is the marks i can see on the bearing, again hard to tell but they look like dents and there is only one way these can be put into the inside of a bearing shell

The Dan Grand Master

The Dan

Posted
Posted

Ok first of all, the oil starvation is the most likely cause but it still doesn't tell you why it failed.

The oil pump/restrictor/head return is a crock of shit. Nissan don't have issues with any of that shit. Yes, improvements can be made to the system but at 3k on a fresh engine, it's still a crock of shit.

The ONLY time oil control is an issue is if it's an RB26 without sump modifications AND it's on a race track at the time of failure.

3k old engine, so it's likely to be only just finished the run in. The fault can be anything from abuse during run in, to incorrect assembly.

And I don't see how any of you other engine builders can pretend to know the cause while only looking at one single BE cap. The picture quality is too poor and it's only one cap.

It doesn't matter how many pictures this guy puts up, without inspecting every single piece of the puzzle in detail, you are all just guessing.

Swiper the Fox Grand Master

Swiper the Fox

Posted
Posted
Ok first of all, the oil starvation is the most likely cause but it still doesn't tell you why it failed.

The oil pump/restrictor/head return is a crock of shit. Nissan don't have issues with any of that shit. Yes, improvements can be made to the system but at 3k on a fresh engine, it's still a crock of shit.

The ONLY time oil control is an issue is if it's an RB26 without sump modifications AND it's on a race track at the time of failure.

3k old engine, so it's likely to be only just finished the run in. The fault can be anything from abuse during run in, to incorrect assembly.

And I don't see how any of you other engine builders can pretend to know the cause while only looking at one single BE cap. The picture quality is too poor and it's only one cap.

It doesn't matter how many pictures this guy puts up, without inspecting every single piece of the puzzle in detail, you are all just guessing.

hear hear...

Good post Dan, this is precisely why i dont post in these type of threads. Without knowing in extensive detail about every factor its just that a guessing game and doesn't help the OP. Take it to an engineer and get a full report with every engine part inspected. The oil control opinion you also have is something i firmly agree with, we are definately on the same page Dan.

Its like those "my cars running rough threads" when everything from AFM's, coil packs, to tail light bulb blown is mentioned.

Tomei_Powered Rising Star

Tomei_Powered

Posted
  • Author
Posted

Thanks for your input guys.

Will have all the bearings remove tomorrow and will take the crank for balancing. Will have the pics up by tomorrow.

Could it be the crank was moved or bent?

Anyway my specs are below.

Im using a RB26 crank (I think it was from a R34 cos the JUN oil pump fits without any collar issue) with a RB25 block

Wiseco RB26 pistons

GTR Rods

ACL Bearings

JUN Oil pump

HKS Oil cooler

RB25 cyl. head

Ran a good 388whp on dyno and few more runs on street before i felt this oil pressure problem.

Anyway, does a quad plate clutch have anything to do with the oil pressure problem?

I just want to know how and why the bearings failed.

Hope this thread will help others to gain experience and hope it wont happen to anyone of us here again.

Cheers.

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