**jay**

iTrader: (1)

Looks like the shock of detting has caused that piston to fail, not so good mate hopefully the rods are fine and you get it built back up again.

I had cosworth pistons in my v3 running 520bhp but they were really noisy even warm but could have been the way it was built.

ossett2k2

iTrader: (9)

Thanks jay
I'm going to start building up this standard donor block so I can get back on the road,I will still have to use my big turbo,injectors etc but I will just put a safe map on there.
I can take my time then and do a slow build over the summer.
I will do a bit more reading up on the cosworth stuff but it's a good name for quality so my best option looks like trying to get hold of a matching piston for the build.
From what I can see and feel,the rods look ok and there is no play in the bearings.
I'm itching to split the block to see everything in the flesh but need to get running asap so will have to wait.

johnlogie

iTrader: (4)

Doesn't look pretty mate.

gazney101

iTrader: (5)

I've got cosworth pistons and rods in mine and it's very noisy, has been from the beginning. I think omega are regarded by many as top quality pistons but cosworth has the bigger name. I don't believe they make them in house though, possibly made in China.
Be sure to have the rods and crank inspected and checked for ovalling.
Good luck

ossett2k2

iTrader: (9)

You're not wrong there mate,made a bit of a mess

Cheers for the tips ganzey,would I be able to check or would they need to be inspected by a specialist?

dj219957

bore looks like it has scores to me.

Steve Whitehorn

iTrader: (13)

Different pistons expand to a lesser or greater extent once they get heat in them.
So some need more room in the bore to expand.
I have had engines with many of the different types in inculding Omega (which are a quality item)

How quiet an engine is ...is obviously also often down to how well it is machined/built.

So given that an engine is a good one and has been built with the right tolerances
The quietest forged piston I have come across are Mahle.

I would also add that certain Cosworth stuff is made elsewhere and then branded Cosworth. I am not saying it is not good, as they have a quality brand name to protect.

Omegas in my experience were quite noisy when cold and they needed a bit of room to expand and sounded as sweet as once warmed up and the thing was being thrashed. (It is a while since I have had any in a Subaru engine...so a builder that has used them recently would be better placed to comment)

Steve Whitehorn

iTrader: (13)

Also make sure you flush the cars system out. Small bits from the engine failure could have worked their way into all sorts of places...so methodically check everything and even bin the odd item if need be

ossett2k2

iTrader: (9)

Couldn't feel anything but I see what you mean when I look at the pics again,as its damaged at the bottom of the cyl then it will be getting scrapped anyway.

Will do Steve thanks,going to take my time with the build.
This donor short block should keep me going for a good while,I will clean my heads and sump up as they will be needed for the donor
Not sure if I need to use my Modine as I'm twin scroll,will look into that.
Also might use my oil pump too,not sure yet?

johnlogie

iTrader: (4)

Rich, remember that I had the head gasket go on my block so if at least do a flush with may be some cheaper oil. The modine on that block has done about 5k. Pump, not got a clue, probably original

ossett2k2

iTrader: (9)

Will run some cheap semi synthetic and do a couple of oil changes over a few weeks then put some decent oil in.
I will leave that modine on then mate if it's only done 5k
Do you know if there's any difference with twin scroll cars modine or would the one on your block be ok for my setup?

johnlogie

iTrader: (4)

I honestly don't know mate

gazney101

iTrader: (5)

Are you planning on using a temporary block that's previously had head gasket failure? if so you may regret it as the bottom end will soon follow.
Yeah you can check and measure your components yourself but I would send them to an engineer to be on the safe side

ossett2k2

iTrader: (9)

Yes ganzey the donor block suffered head gasket failure.
I know most people advise to refresh the bearings after a head gasket has gone but time and funds won't allow this right now,I will just have to take the chance and hope I'm lucky.
I'm sure there are plenty of cases where head gasket failure doesn't always lead to the bottom end failure so I will just have to keep my fingers crossed.

JDM_Stig

iTrader: (3)

I know it might be daft but for the money it will cost to drop this temp block in( gaskets etc arent cheap),
wouldnt it make sense to buy a cheap ****ter for a while, then you can do the imprezza at your leisure and properly.

ossett2k2

iTrader: (9)

Good advice mate and I will defiantly be taking my time and using quality updated items to rebuild the forged block.
But I've only paid £48 for standard oem head gaskets so all in all it will come in at under £100 to get this donor up and running,plus my time and a few scraped knuckles which I don't mind.

JGlanzaV

iTrader: (3)

I would heed the advice regarding bearings.

Ask any engine builders on here about bearing failure after HG. There is a reason they refuse to do just headgaskets.

You will end up with a car off the road in the near future I am sure, and end up in exactly the same situation as you are now. Honestly the best advice is buy a ****ter and don't bother with the temporary block.

It will end up costing twice as much and it is essentially money down the pan. I'd rather have something reliable and build the scoob up as and when and do it properly.

In all my years of modifying cars, the one thing I have learnt is temporary never works. Build for permanent.

ossett2k2

iTrader: (9)

It's defiantly not ideal JGV but I now have all the parts,gaskets etc.
If I bought a runabout+insurance+keeping the Scooby insured it's going to work out at more than £100.
I'm not ignoring advice as it all makes sense but I've started building up the temp engine and the gaskets I've bought can't/won't be used on the forged build.
I suppose I'm not paying for any labour so that's a big chunk of money saved,also have all the equipment needed plus I'm getting quite good at removing the engine now.
Like I say fingers will be firmly crossed and hope for a bit of good luck.

JGlanzaV

iTrader: (3)

I hope it works out for you Rich! Fingers crossed

The Rig

iTrader: (13)

Why do big ends fail if not replaced at the same time as new head gaskets ?

Slightly more compression on old bearings ?

Cheers

gazney101

iTrader: (5)

Overheating causes big ends to oval and warp

JDM_Stig

iTrader: (3)

maybe its if the water and oil mix, causing the oil not to lubricate correctly ?
If its just blowing into the water system under pressure you may not get the same problems.

BrownPantsRacing

iTrader: (6)

To be honest I'd been told the same about bottom end failure after head gasket failure, but can't remember the reasons why. From memory it was mostly down to contamination in the oil causing premature wear on components.

Steve Whitehorn

iTrader: (13)

Fingers crossed. Hope it all works out.

(If you have a change of heart and do decide to do the bearings.
I have couple of good instructional vids on my PC sat here)

ossett2k2

iTrader: (9)

Nice one Steve,the vids will come in handy for when I get around to the forged build so will give you a shout

On inspecting one of the other pistons I have found fracture lines in exactly the same place as the one that failed! So I won't be reusing them now.

edsel

iTrader: (2)

I have mahle pistons in mine and you wouldn't know theyre in there even when cold. I reused the modine on my build but It wasn't a blown engine just worn out and badly built. I placed a magnet inside the modine to see if there was any swarf and vacuumed the inside using a small peice of pipe. How did you measure for the head gaskets? Because I wasn't confident measuring and didn't trust the local machine shops I handed the long block assembly and machining to a pro. His labour charges were a very small part of the build. He also supplied parts at similar oft. Lower price to what I could buy them online.
Check the crank hasn't been ground and fitted with os bearings, subarus don't respond well to ground cranks. Reusing the oil pump shouldn't be an issue as long as the prv isn't sticking.

I've yet to be convinced that subaru engines can be built on a tight budget. A diy refresh with rings bearings gaskets and a hone is going to cost over a grand.

ossett2k2

iTrader: (9)

I just went for standard 1.6mm gaskets edsel.
It's a standard donor block I'm using with my standard heads so was thinking this would be ok.
This is just for short term,saying that it might be in for a while?
As I need a new block and now after inspecting one the other Pistons I have taken out,it has fracture lines in the same place the other failed so they will be going in the bin too!
Might just end up saving for a proper pro build for long term,need to have a think.

ossett2k2

iTrader: (9)

Well finally the engine's built back up and I fitted it today,all done

I still have to wait a little longer to turn the key tho.
Was hoping for my delivery from opie today,oil,filter,coolant but sadly it didn't turn up

Guess I've waited this long so a few more days won't hurt,proper looking forward to driving it again

bustaMOVEs

iTrader: (31)

Well done dude, bugger you cant start it though, not wise with no fuilds

JGlanzaV

iTrader: (3)

make sure to prime it first by removing the crank sensor...