4 replies to this topic

[andywilson]

hi all

 

as some of you may know, i'm putting a z20let into my kit car.

I was doing a balancer shaft delete so removed one of the crank journal thingys and saw this:

 

 

 

first time I've ever seen anything like that.

anyone know a likely cause?

 

pistons looks fine, bores look fine, oil looked fairly clean, nothing suspect at all about the engine.

I've inspected all the others and they look fine

 

 

also...I think I know the answer to this... but is it possible to just replace this half of the bearing?

 

thanks, andy

[Nev]

Blimey. Just replacing 1/2 a shell rather than having that ripped up thing must be way better surely ?

[Dave E]

We found one of my shell's was the same when the engine was stripped down. The reason for my rebuild was boost passing the piston rings which meant the turbo wouldn't hold the proper pressure. This also had the side effect of overheating the oil and its that that we believe was the cause for the shell delamination.

[andywilson]

hmmmm, tis a strange one.

 

I agree Nev, you'd think it would be better, however having one half of a shell worn and one half new may have some adverse effects? not sure really

 

I think i'll stick half a replacement 1/2 shell in there and see how it goes. soon as it's in and running i'll do a compression test to see what the rings are like.

 

thanks chaps

[Nev]

@Dave, I wonder why only one shell would delaminate, surely all would blue/discolour and start failing in a similar way? I reckon it might be due to oil starvation on that journal for some reason. With that in mind Andy, it might be worth poking a wire up the oil hole and clear out any possible debris. Also, if that is the central bearing (which it does look like), it might be sideways pressure on it causing the side of the shell to be stripped, as the central bearing acts as a thrust bearing. Worth checking for lateral (end to end) play in the crank...

Edited by Nev, 22 July 2013 - 09:13 PM.