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$$ Spun Rod Bearing In Fully Built Rb30 :(

ZT-R

By ZT-R,
in Engines & Forced Induction

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luke gtr Grand Master

luke gtr

Posted
Posted

only the one rod looks to have heat damage.

so, id say blocked oil feed to that rod.

then bearing shredded.

and those pieces have gone through the rest of the motor.

this has caused the damage to the other bearings.

seems like this would be possible.

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ZT-R
ZT-R

Been getting some pic request, so i will just post a few here.

luke gtr
luke gtr

shimming the spring, yes.shimming the plug, no.

NYTSKY
NYTSKY

You can get stock Rb30 cranks here for a cup of coffee plus shipping.

RobertPaulson Newbie

RobertPaulson

Posted
Posted

The heat damage is consistent with running for a very long time after the bearing has suffered complete failure. You've had a temporary starvation of oil at some point. Every one of those bearings shows it. The mains are polished and the bigends definitely show it. The bearings for cyls 1 & 6 are going to be the worst because they are the last in line to get fed oil from the main gallery in the crankshaft. The mains don't suffer the hammering because there is minimal lateral loads unless a missfire or detonation occurs. That's why they are just polished.

The rest of the big end bearings partially survived because when oil supply was regained, they continued to be lubricated. 1 more second without oil and #6 would have looked like #1 does and another 3 seconds and the rest would look like #6 does now or worse.

There is only 0.0001" difference between what #6 looks like and what #4 & #5 look like. That's all it takes. The damage was done and then you continued to drive it for what looks like maybe 1000 miles. You probably didn't hear it due to exhaust noise and the fact you might have been relatively gentle on your new engine.

It's disconcerting that the oil pump hasn't failed. That would be an easy find. Are you sure there is no crack in the inner or outer gear? You have to look very closely (by the sounds of your descriptions you know what you're doing)

Also measure the outer gear in 6 places to make sure it's still round as well as the inner gear if you can.

I don't think this is going to be the cause though.

Any idea what clearances were run?

ZT-R Enthusiast

ZT-R

Posted
  • Author
Posted

The only thing I did was put a few shims on the oil pump to back off some of the pressure. I had it down to 50 at idle and above 100 at 3200. Before it was idling at 80-90psi. Could that have done anything? I did that about 500 miles ago.

Ben C34 Grand Master

Ben C34

Posted
Posted

you can put a shim (washer) under the head of the bolt and it will back it off.

Not a shim under the spring.

of course. Was a bit early in the morning for me!Such a shame to see the damage man. All the best.

XKLABA Grand Master

XKLABA

Posted
Posted

i got a whole running rb30 for $50, kept the block and crank and recycled the rest

was once given a complete bottom end before 30s where done in GTRs and scraped the idea and binned the block

that is a sweeeeeet Z, would love to have one with a 2630 in it, mad skids

every thing that needs to be said has been about the damage, it def looks like oil supply issue where it be a air surge or not enough flow to the bottom end

R.I.P.S NZ Collaborator

R.I.P.S NZ

Posted
Posted

I agree it has been an oil supply problem then continuing to drive,

I supplied just a bare short block and had no input into anything else, such a shame for such a nice car and a forged bottom end.

There's a few things of concern I have seen in the pictures and I've been over everything with the owner in about 50 e-mails over the last few days and am more than happy to help get him going again,

Rob

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