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Discussion Starter #1
hi guys,

my friend bought a gtr & recently built a new engine for it (rb26/30). he is not computer literate hence why i am stuck doing the run around & research for him :)

when the engine was built, we ran it for 30min & it had a strange sound at 3000rpm when free revved which was at crank speed & the noise disappeared after 3200rpm. drove around the block & noise would start @ 3000rpm & continue as the revs get higher.

the engine was stripped, found it was way over full with oil and these are the big end bearings out of it, what are the opinions of people as to what would cause the noise and marks, i.e. oil level too high?



 

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look to me like they were built to tight and very bad oil as in poor assembly, the blueing is heat build up, you can see on the shells where they have been binding..
 

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A dirty build, looking at the scoring, and bearings clearance too tight. Plastigauge these shells and see how tight they are.
 

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Discussion Starter #7
i was under the impression that these acl bearings are in fact heat treated from factory hence the blue colour?

some of you have referred to oil being the problem - are u referring to oil starvation here?

i have done some research & found that too much oil will cause 'cavitation' where the oil turns into a shampoo, this then starves the engine for oil as the oil pump is moving oil & air pockets
 

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The blue colouring on the backs of ACL race bearings is normal out of the box, also a little colouring on the bearing surface is also normal, nothing to do with any heat from the engine.

Rob
 

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Discussion Starter #9
how about the deep marks on the 2nd and 3rd bearing in
the first picture, any thoughts?
 

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Bits of crap if you ask me. How did you over fill the engine with oil? Did you not check? Unlucky though mate on the build, hope it goes better next time :)
 

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The blue colouring on the backs of ACL race bearings is normal out of the box, also a little colouring on the bearing surface is also normal, nothing to do with any heat from the engine.

Rob
spot on...finally someone posted who can actually read bearings. If it was oil starvation and excessive heat the bearing faces would be black and not just a localised silver colour.

bit of foreign matter in the engine hence the scoring.

a few of the bearings are wiped which i would say has occurred due to not correctly priming the engine (turning engine over with key while CAS is disconnected is not an acceptable method)

there appears to be concentrated loading which over filling could be the possible cause.
 

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Discussion Starter #12
this is the thing - the mechanic added oil to the engine & my mate noticed it was overfull but the workshop said this is ok.
30min later, engine noise was discovered & they didn't even think or imagine extra oil would make this sound...engine builder dropped the oil from the sump & it had 10.5ltr! the big sump can hold up to 7.5ltr
 

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lol thats a big over fill. Does the builder know what he is doing. Because it looks like he's made a few mistakes to me. Over filling engine with oil, not cleaning engine properly before build and then keeping it clean, not primeing and oiling everything up when installing the bearings, and thats what you know about.
 

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Major contamination and generally nasty. Those divots i suspect would have been there before assembly.
Send bearings and oil sample to acl and they will wright a report(normally at no cost)
Jason.
 

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Another note although bearings have obviously had contaminants thru i doubt you would get any audible "noise"
More than likely what you were hearing was caused by crank etc slappin the oil.
Jason.
 

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Discussion Starter #16
do you think that excessive oil level can make that rattle noise though @ 3000rpm?
if i describe it, sounds similar to a spun bearing but obviously not a spun bearing

also the marks on the bearings, are they are a result of excessive oil?

here is an explanation of the noise to understand better:
 

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With plugs out I'd say it was "acceptable" for most although I agree, there definatly are better ways.

Rob
 

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Sorry for OT post, but what is an acceptable method?
we inject oil under pressure through the oil pressure sensor fitting. Removing the oil cap and looking at the cam bearing for oil seepage will confirm the system is correctly primed.

this is the safest method...so in my opinion the only 'acceptable' method.

but everybody has different ways of doing things.

i bet the plugs were in Marko's friends engine and id assume the most wiped shells were rods 1 and 6.
 
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