Cheers!

Personally, without seeing it in the flesh, is that all you see is carbon buildup that extends onto the top flat rim in places...........

What ppl seemed to forget to ask is... Why did I get HG failure?
With not asking they just go the route of having the HG replaced.

Then in a short space of time something else rears its ugly head.

Which was the problem in the first place.

my hg went on one car a year later the bottom end , so paid twice in effect , second car hg went bottom end sounded fine but i said do the whole thing , a crank bearing was on its way out so lucky i did , crank was saved , he said failure rates in a 2 litre after hg done about 25 per cent , failure rates on a 2.5 about 75 per cent fail within a year , the bores tend to become oval after around 80k miles so need a rebore but a minimal rebore , the valves normally need adjusting too , nothing to say it will go but in my books not worth taking the risk so just get it done in one hit , the first car went around 90k miles it’s now scrapped but hit 193k miles and engine is still running fine , don’t forget to get arp bolts done , if it has a sensible tune with not too much boost that helps too , real shame there are issues on the 2.5 as it’s a great engine , forging just gives that extra piece of mind , but it’s not cheap at around 5k£ to get it forged , i just look at it long term if i’m keeping a car for 193 k miles it’s worth doing , that’s three rebuilds i’ve paid for now , just wondering when my latest fsti 2.5 engine will go , it’s running like a train now , money now saved for a possible failure

I'm not talking about the black, you can clearly see material nibbled away and holes in the skirt.

May well find crank bearings gove up the ghost in very short order as well. Sounds like it needs a full strip down and refresh

In reality when the pistons were carefully cleaned up there was one microscopic flaw on one crown edge which may well have been corrosion the biggest killer of engines due to short run condensate and standing. She is still running well 10k on from the head gaskets and head skim rebuild.

As a point of clarity there isn't any 'skirt' visible in the photos. There may well be holes in the skirt but the pistons were not removed so we will never know!

:thumb:

My bad description, the raise ridge round the upper face of the piston. But pot Mark's in the metal are clearly visible

Just a camera artefact with all the carbon. It was just a machined finish all over even at 10x magnification with a spy glass.
No cracks in the heads either.

This is exactly why Paul Finch wont do a head gasket without inspecting the bottom end.

got any pics of them after being sorted? the one at the top could well be carbon, i would be totaly amazed if the others are just camera affects


https://cimg2.ibsrv.net/gimg/www.sco...76807f199.jpeg

https://cimg7.ibsrv.net/gimg/www.sco...3930faa04b.jpg
This is det, no det on the pistons in the thread.

eh? det isn't only blowing sections off the piston. So if it isn't det, what are the chunks missing from the piston as highlighted?

The bits you have highlighted are carbon,the pistons have far too much carbon to be any det going on, first sign of any high cylinder pressure / heat incidents would burn off all residue carbon, only leaving a fairly clean piston, the above all have high oil consumption symptoms.
The single indent you also highlight is piston position mark.

If so then i stand corrected, so if its not det, whats nibbled the edge off the rim of the piston? because that is def an indent rather than a build up

I can see what you mean about the nibbled part of the piston, but I am sure its standing proud of the surface not indented, most of the high oil consumption 2.5 pistons have identical carbon deposits.

carbon bits arnt important so rather irrelevant. its those pesky nibbly bits

Time you invested in a decent screen. Those are all carbon/ash deposits and stand proud of the crown I wish now I had taken a picture of the clean pistons!

interesting video from the US,


I keep people saying why don't US cars fail, but the vid highlights the same issues in the US as here

The states had all the class libel issues , where subaru was paying out a lot and where basically told to accept liability for the engine failure issues , shame the uk issues have not been accepted as subaru’s fault

My MY11 has just suffered headgasket failure at 64K, will have to see what else needs fixing when the engine is out and may as well get the clutch done at the same time.
Only spotted it because of a slight performance drop when overtaking on a dual carriageway, noticed the temp gauge up at hot. But really don't know how far I'd driven it in this state.
Looks like it might only a water gallery to cylinder leak, oil still looks good, am in touch with a couple of local Subaru specialist, who get good reviews on here, so will get it sorted and have some real gaskets fitted.
Doesn't matter how you treat them, and mines had a cushy life, but if you have naff parts installed from day 1 it's just down to luck, thank you Subaru.

get the bottom end done too , it’s a false economy to not get it done , it will sound and appear fine but only stripping it will reveal the wear and tear , forged pistons plus arp head bolts and cosi hg , the bottom end failure rate is around 75 per cent on a 2.5 v about 25 per cent in a 2 litre , ive been there before twice where bottom end appeared fine and it was not , first time it went within a year , second hg fail i said do the whole lot , one bearing crank shell was on the way out but crank was ok

I can see what he means, so wouldn’t say the new screen comment is totally fair. Even looks like there’s holes nibbled out and the shadow drops in to said holes.

Only thing that could give that illusion is if the lighter part is actually lint from a rag or something and it gives the effect of it being holes.


https://cimg8.ibsrv.net/gimg/www.sco...7e6e821b84.jpg

abre , what area do you live in , down south there is subaru4u , fb tuning , paul finch motorsport , just to name a few good ones , i’m sure they are many others out there , it’s worth using a trusted builder as there a rebuilders 😁and rebuilders 😕😢 out there

Take it from me those are white ash deposits that sit proud of the crown and have black carbon surrounding them. When the pistons were cleaned there weren't any flaws in the machined surface. The engine is still running on skimmed heads for those that are interested and still has only ever seen V-power in its 10years of life.

Thats great and all but I was just making a point it looks like damage & I could see where he was coming from. “Time you invested in a decent screen” just seemed a bit aggressive of a reply that’s all.

Hi VXR2010
I live up in Saddleworth which is between Leeds & Manchester & there are a few recommended builders to choose from, like Richard Henry, HDC & CAMS all with a good Subaru reputation.
It will be getting either Cosworth or RCM head gaskets & will have studs fitted as well.
I've discussed the bottom end with all of them & depending on who I choose, the plan is to first see what the compression's like, then see what the bores & pistons look like before taking their advice on whether to split or not.
I have no plans to take the power over it's current 320, but I do want to have a good reliable engine as it's my daily drive. So if there's any doubt it will be having the bottom end done.
Also going to assume at 64K it'll be needing a new clutch, so could be quite expensive!
Andrew

I recently rebuilt my 08 STI engine in almost standard trim. The clutch plate was showing signs of wear but flywheel and pressure plate were fine. I replaced just the friction plate, release bearing and flywheel bearing. The parts are available separately from a main agent at a reasonable cost too. Being a road only car and not on big power, the standard clutch is well up to the job.