Bore has tiny gouge in rebored cylinder wall (worried)

[RB25Detonator]

Hi guys. I got my RB30 block back from the machinist like 3 weeks ago. I just started cleaning the bores and noticed a tiny gouge (what ever you call it) in one of my bores. The block had a rebore of +1mm to suit 87mm pistons and torque plate hone. Originally it was going to have a +0.5mm rebore but machinist called me up saying the scores were too deep to clean the bores up so then I had to purchase +1mm oversized pistons and they bored and honed to that. 

I can feel it definitly with my finger nail. I reckon it's about 0.2 or .1mm deep probably. I'm worried now. I want this build to last years as it will be my daily streeter. Will this cause damage to my rings and/or cylinder bores?

[GTSBoy]

Yup, that's f**ked.  Corrosion pit, by the looks.  Needs to be bored out.

[RB25Detonator]

Aw shiet. I was kinda thinking it would be.
JB weld it by smearing small layers on the pit? Lol
I really dont wanna rebore it again. Im gonna measure how deep it is today with a dail bore gauge and see what my machinist have to say

[Ben C34]

I would not be happy with that, but out of curiosity is it low enough that the rings even go over it? 

[RB25Detonator]

12 hours ago, Ben C34 said:

I would not be happy with that, but out of curiosity is it low enough that the rings even go over it? 

It sits 70mm down the bore.

 

The pit is 0.1mm deep. Bores have been machined with a piston to wall clearance of 0.04mm to run my hypatec RB30ET 87mm pistons.

fml. dont know what to do at this point...

 

 

[Ben C34]

1 hour ago, RB25Detonator said:

It sits 70mm down the bore.

 

The pit is 0.1mm deep. Bores have been machined with a piston to wall clearance of 0.04mm to run my hypatec RB30ET 87mm pistons.

fml. dont know what to do at this point...

 

 

Well that sucks. Add more boost and hold it on the limiter to show it who is the boss   ...

[admS15]

Just send it..

[AngryRB]

Man thats shit, how can they not see that, im no expert but even those hone marks look rough.. 

Im interested what piston to bore clearance they did as hypatec pistons dont expand much..

[RB25Detonator]

7 hours ago, AngryRB said:

Man thats shit, how can they not see that, im no expert but even those hone marks look rough.. 
Im interested what piston to bore clearance they did as hypatec pistons dont expand much..

 

0.04mm clearance which is just above the minimum clearance of those hypatec pistons of 1.5thou.


I've left my machinist an email. Just waiting on what they'll say. So theres no other option than reboring it right?
No one's tried a little tac weld then grind down with dremal and rebore/hone? Lol bare with me, this is my first engine recon and im just trying to lay out some options

 

Edited April 8, 2019 by RB25Detonator

[RB25Detonator]

[emoji23]

[RB25Detonator]

Can anyone confirm this?

[Ben C34]

24 minutes ago, RB25Detonator said:

Can anyone confirm this?

Well it's not low enough for the rings to not go over it, but in the scheme of things it probably wouldn't matter. I would be leaving it alone before trying to weld it, that's just mental.

I can't see how it would cause damage, but it's not nice knowing it is there, you will always be thinking about it for the rest of your life....

[Duncan]

Depends on how big a problem it is for you if the engine fails.

If it fails, you have written confirmation from the engine builder that this wouldn't cause an issue, ie their problem to fix. Depending on their attitude they might do the right thing no problems and fix it, or you might have to fight which can be expensive.

Alternatively, if you are pushing it hard and can't accept anything less than perfect, you need to bore it out another .5mm.  But that would be at your cost as you provided the block which had pitting that was uncovered during machining, and you will need new pistons and rings as well. Expensive but you get piece of mind.

I'd have to say, I wouldn't be happy that the shop didn't tell me about the problem (either because they didn't see it or because they didn't want to pass on bad news) before it left so I could decide what to do.

[RB25Detonator]

Yeah. If the bores were 86.5 with that pit, i would have gone back and told them to clean it up by taking another .5mm off to make it 87mm. But these bores are already 87mm and i dont even know if there are 87.5mm pistons out there for RB30 (and if there are, i bet their expensive). Plus ill be left with about 3mm of cylinder wall thickness. So yeah your right, would be expensive journey.  This is a cheapish build for street use. The hypatec pistons and rings only costed $300. Using stock rods, crank with collar and neo head with usual bolt ons. Will be limiting revs to 6500 and will probably only expect 250-300kw with usual bolt ons. Its ment to be my daily for driving to and from work ect... that i want to last for a long time as i dont have time to open it up again. But i guess im just going to go ahead with the build and just be prepared to open it up again (hopefully not).

If the rings catch onto that gouge/pit, what items should i expect to get raped? Will crank and bearings still be ok? I would imagine it would shatter the rings and probably the piston and bore (hopefully wont lock rotating assembly?) I dont really mind if bores get damage cos blocks are cheap. 

Thanks guys for your inputs!

Edited April 9, 2019 by RB25Detonator

[admS15]

For that sort of use and power i wouldn't worry about it. It wont effect anything other than you know its there.

[Ben C34]

Don't stress about the rings catching. I hereby give it internet mechanic approval.

[Duncan]

6 hours ago, RB25Detonator said:

This is a cheapish build for street use

Then personally I'd take the chance and run it.

[admS15]

Ive put 2 stroke bike engines back together with worse cylinder defects than that and never had an issue with rings catching.

If it bugs you, get hold of another 30 block and have it bored to suit your pistons. Your only loss will be the $ you've spent on machining and time.

Personally I'd just use it.