Rb25\30 Marked Bores - Anyone Have An Idea On Cause?

[The Mafia]

Dont suppose you have some micrometers and a dial bore gauge? I thought cast pistons with high silicon content usually run tight piston to bore clearances. Perhaps its .0014" or thereabouts...

Sorry mate, but I will give a mate a call today - he has all of this gear.

[Adriano]

I agree with trent, it will either be too tight a piston to bore, or ring gaps. For your application, i would be running at the higher end of the specs for piston to bore, and maybe add 2 thou to the top ring gap, depending what the spec is. If any of the clearances are less than they should be, i would be asking for the machining costs back.

[The Mafia]

I'm booking the blick into a workshop today. I'll give them a list of things to report.

Hopefully they come back with some answers.

Thanks Trent and Adriano - This information is very helpful.

[DVS JEZ]

any news yet?

[The Mafia]

Sorry mate, no news yet. Work has me flat out, and I'm trying to find time to lift the block out. It's all disconnected, just need to unbolt the gearbox, and lift it out.

[r33_racer]

Any further developments here? Or still been too busy?

[James_03]

Are they 87mm pistons?

Still looks like a factory hone with that much lip on it, don't normally see that on such a fresh motor.

Go back and look at my thread if you can find it, exact same pictures almost and symtoms. Engine builder totally fudged the piston to bore and gave it almost double on myn.

[The Mafia]

Hi Everyone

Here are the rest of the bores before the engine goes off for inspection.

[cactus]

Pulled the head off my RB30DET not long ago and when I inspected my bores they looked exactly the same as the photos you have posted. Engine buildler suggested that it wasnt scoring and was actually fuel lining the boors or something like that ... will be interesting to see what you get back from your engine builder. Mine wasn't using much oil.

[The Mafia]

Here is an update from the first inspection drop off. They are pulling it down this week, but a quick look they said:

The Deck finish was really rough - Too rough for a Metal Gasket (I have a cometic 3 layer)

The pistons could be moved A LOT in the bore - Piston to bore clearance could be shitty

No signs of over heating

Mine compression tested really well. But there are scratches in 2 bores that are too big to ignore.

Will have an official report from them by Friday, then to the next machine shop. They will inspect and then rebore & hone. Friend of mine is a qualified mechanic, build 50+ LS1s (remember the oil burning issue) is going to put it together for me. He's very switched on.

Going to get CP pistons, and Spool rods, balance and assemble. Will re-use the bearings if they are ok.

Time to go, talk soon. Hope you're all well.

[DVS JEZ]

if the pistons could be moved alot doesnt that mean excessive clearance?

could possibly be excessive temps causing the pistons to grow and come in contact with the bore,

so was the marks definately causing issues?

[STATUS]

what were the bearing like? any pics?

[James_03]

Yeah would be interested to see the condition of the bearings.

In any event I would be reluctant to re-use them. If your going spool rods then you will most likely need crank work/new bearings anyway.

[STATUS]

Yeah would be interested to see the condition of the bearings.

In any event I would be reluctant to re-use them. If your going spool rods then you will most likely need crank work/new bearings anyway.

i just wanted to see if they were hammered, could have been some abnormal combustion going on.

[The Mafia]

Hi Guys. Post today is limited because we have no power. Got some pics though. Oil pump pics later tonight \ Tomorrow morning.

Sprry about the delay in getting back to you all. Took the engine to a "workshop" and they said "COme back at hteh end of the week. 4 f**king weeks later I went and got it regardless. No report written up, and wanted payment. I gave them half for pulling the motor down.

f**k some people around this town are USELESS.

Anyway.

I have a few things to report, and some pics.

1. The Pistons look normal, but with weird combustion marks. Clean on inlet side, dirty as f**k down exhaust side. Might be normal actually.

2. Pistons have 0.5 stamped on the top. Nothing else. (Pic below)

3. The Big End bearings look like brand new. No marks, no hammering, nothing. Clean as a whistle.

4. The Oil pump - Has circular marks, which look like too much crank thrust to me.

Anyway - Pics.

Edited January 3, 2011 by The Mafia

[GTRNUR]

Have you had a close look at the hone patern on the cylinders? It seems to be a little all over the place. Its possible the hone is responsible for the rings not bedding in properly, resulting in a lack of lubrication that then caused cylinder gouging. Have a look for more information here:

http://www.hastingsmfg.com/ServiceTips/cylinder_bore_refinishing.htm

[fatz]

Bottom Ron the correct way waround

[The Mafia]

I was wondering the same thing - I asked for hastings rings, and if they are, then I'm thinking they may be.

And, the hone marks definitely look shit, I will bring this up during the real inspection.

[rockabilly]

any news?.

[The Mafia]

Not yet - I can't really afford to send it to the inspection crew just yet. Give me a week or two and I will send it down.

Will definitely bump this post when I get some results.