The main and rod bearings are from my 3k total mi stock 8 psi FI Z engine.

The finding is a heavy or hammered wear pattern at the top and bottom center rod bearings. Only one of the mains looked abnormal.

My engine machinist who has worked for Keith Black and is a writer for Sunnen equipment said it was due to the rod flexing and stretching under load.

In summary, any loads over stock maybe harmful to our engines health, So let the forged internals begin!!

I will not stay away from the "dark side"

 

One more angle... the photo does not tell the whole story well.

 

They look like they have seen better days. The mains that came out of my stock 6000 mile motor barely had the grey surface coat removed from them. At least yours weren't down to the copper yet

 

Good lcuk flexing those Pauters

 

Maybe in a vice

 

EXCELLENT PICS and post..thanks for sharing. This could be why even properly tuned engines are snapping rods and spinning bearings....at relatively low boost levels.

 

Good info. What oil were you running?
Thanks,
Gary

 

Thanks GQ, that's the reason why I posted the photos to inform everyone in the FI group of what maybe going on in the VQ before she BLOWS!

A lot of lost engines maybe attributed to bearing failure in the early stages.

Once a bearing spins it's hard to tell what happened, rod, rod bolts, detonation.

What came first???

I have changed my oil and filter first @ 600mi second at 1500mi GTX 10-40 then the last time at 2600mi W/ Castrol Syntec.

 

I have been studying the technical specifications for the Z's bottom end. I was surprised to discover that Nissan engineers allow a connecting rod BEND tolerance of .0059" (large) and a .0118" (very large) TORSION specification. See picture below.

For comparison, the main bearing to crank specification is for a clearance no greater than .0028"

This tells me that they allow a large(r) amount of variance in what makes a connecting rod acceptable. Curious.

I'm also wondering if .0028" on the mains is enough gap to allow satisfactory lubrication.

For anyone that is doing an engine build-up, I would highly recommend that you read and understand pages EM121 thru EM135 in the service manual (2004 version). I know you would like to believe your builders follow all these specifications (piston, ring, crank/rod bearings).

 

hmmm... thats strange...

From the pictures only... i cant see it in person...
The bearings I took out of my engine looked exactly like that... and one of them was worn more than the others...

crap.. too bad i already threw them away and i took pictures of everything but that as I took my engine apart...

I even remember looking at the bearings and going.. "oh thats why you change them each time.."

And my engine only had 90 something miles on it.... <-- not a mistype on mileage.. wish i could go get them...

did anyone else check your bearings after you took them off?

 

Does anyone know what the different Grades of the bearings mean? They show grade 0 through grade 2 available for the bearings, is it material or dimension differences?

 

I just answered my own question, the manual says the grades are for diameter needed based on the crankshaft dimensions, so I guess that if your crankshaft didn't get wear you just used the same grade bearings.

 

What are the aftermarket options for main (engine) bearings? Also, about the grade... Will the individual assembling our engine know which to use by lookin at our crank?

 

Yes the manual says the crank will be stamped with the grade.

 

Exactly what I was going to say. This AMY very well the reason that well-tuned engines like mine just went... who knows... without datalogging, we really cannot know for certain why a given engine goes.

 

Hey Gurgen,

Sorry what happened with your motor, I am the guy that was at Technosquare when they were replacing your oil jets.

 

Oh hey... Good to have met you. Thanks for the sympathy...