Haunt

Hello

I have a 2008 WRX STI hatch.

I think my head gasket is on its way out. The overspill bottle is filling all the way to the top when hot, leaving visible patches of coolant in the engine bay and It’s not going back into the radiator when it cools down. I’m having top the coolant in the radiator up every few days to stop it overheating and when I take the cap off the overspill bottles bubbles up. The systems been pressure tested and new thermostat and caps fitted. The oil and the coolant is not a different colour and the car does not overheat when under boost either.
Is there anything else it could be.

I may at some point in the future get it to 400bhp, it’s currently at 360. Is that possible to get that with a semi closed deck reforge or would I need closed deck conversion.

If I decide not to increase the power at all is there any benefit having a semi or fully closed deck over a standard rebuild for the head gasket?

Apologies for the long post.

Vxr2010

oh dear been there twice before , if it was me i would stick with the power you have , limitations are strength of gear box , and sound reliability , i saw a cs400 with a cracked liner , not saying you can’t do more power but i would not , the issue you have is if 2 litre hg go then there is a 25 or so percent chance the bottom will go within a year , a 2.5 it is more likely to be a 75 chance of bottom end failure , the two rebuilds i have had on a 2.5 , the bottom end failed within the year , no extra power added , cost me twice , the second 2.5 that hg failed bottom end sounded fine , i said do a full rebuild , i think it was number 3 bearings starting to go , crank shaft was ok , sorry in reality budget for a full rebuild ☹️if you stay at 360 pistons rods i think are good to 400 or so , definitely do arp head bolts 👍

Haunt

So would semi closed or fully closed reforge fix the potential bottom end failure issue?

adam.pah

If it's a head gasket then you need a full rebuild as Vxr says. It won't be cheap but that's the reality of owning a 2.5 engine.
I would speak to Alyn at AS Performance to discuss your options, he can tell you the best route to go and how much things will cost. I hear so many stories of people getting rebuilds that just don't last that I wouldn't even shop around nowadays.
I've had friends use Enginebuilder with good reliability too.

NOSSY_89

Looks like he has a STI @Vxr2010 so power could be upped a lot more before the gearbox becomes a concern.

There are two different things there mate, semi closed deck and fully closed deck. These are different to forging and in theory when you do a fully forged rebuild you tend to change the bearings. So you're changing the part before it fails. You would have to do this any way if your bottom end goes. The benefit is you can save the crank so you save yourself money there.

Speak to Alyn at AS Performance. @domino46 had a rebuilt hatch so he could probably give you some idea of what was done and other stuff to consider.

Vxr2010

i can not give as much advice on the heads , i’ve never changed mine for any thing else , i think heads having minimal input on bottom end life , good map , not too much power , a good set of pistons , acl crank bearings , add a lot to making the bottom end better , heads wise as above use studs not bolts , i’ve heard some cars running 700 odd bhp , but it’s a curve of how much power v reliability , and how your mpg is , the more power the more likely things go wrong and engine does not last as long , my cars are Fsti , less prone to hg or bottom end failure but they still fail which is why i have a spare forged engine , as they are running around 330 to 340 bhp , plus it’s a different engine to the impreza sti , a small turbo so not much lag and up to 35 mpg , run more power more mods needed and more fuel used , mines a daily so works well as it is for me as it is 👍

Vxr2010

sorry did not see the sti part 👍 len at subaru4u is good , richard at Fb tuning is again very good ,as above use a recommended engine builder is very important , even now seeing it’s a 6 speed i still would run it at the power you at ,as i said with mine they are daily drives so mpg and reliability are up there for me , all i’ve done on mine sports down pipe cat and a re map , and coilovers , my mates Fsti he threw a bigger turbo at it etc, not long later crap mpg then the engine failed he regretted it all 👍

Haunt

Thanks all for the advice. 👍

yeah, I think I’ll stick with my 360bhp as it’s a daily driver also, don’t want the hassle of potential problems that come with higher power.

Will look into a standard non forged rebuild 👍

adam.pah

Tbh, I don't think there's a massive saving in not going forged. Most of the cost is labour and ancillaries, the main engine components probably don't add much. It might be worth having the machine work done for 14mm head studs at the very least.
Do it properly, with a decent builder and you'll be trouble free. Try to cut corners or save a grand by using someone less reputable and you'll end up having problems. Trust me, I learned the hard way!
You probably need to budget £5-6K for a decent build. Pay once, cry once, move on.

NOSSY_89

So @adam.pah is correct. If you're going down the route of a rebuild you might as well go forged. A large amount of the cost is labour. Try and leave room for added power. You want some headroom at least rather than have to rebuild the engine to take an extra 50bhp. 14mm head studs seems to be the way to go.

Vxr2010

you will need forged pistons , but probably not rods , but don’t need to raise the power 👍

Vxr2010

forged pistons as the 2.5 especially the sti ones have the ring land issues so very unwise not to change them , block will probably need a minimal re bore so forged pistons will drop straight in 👍

adam.pah

To raise power you're starting to get in to the territory of changing turbos, intercoolers, injectors, fuel rails, etc.. It starts to get expensive then. The difference between a 360bhp car and a 400bhp car is negligible given the cost and bigger turbo means more lag, so if this is a daily I think 360 is a nice power level on balance of things.

If you really want something faster my money would be to swap to a twin scroll setup instead. I have both and my twin scroll is the faster point to point car on the road even though it has slightly less power; the TS has more torque though. Most people wouldn't do this though because you lose the 'burble'.

NOSSY_89

You could get away with a much bigger turbo due to the extra displacement. With it being a hatch the injectors and top mount should be fine. Also no need for fuel rails to be changed unless you wanted to. But like I said keep it where you are but leave enough headroom for more power later.

Haunt

Had some quotes from TDR which is nearby to me.

Normal rebuild £4602

Forged Engine at £6345

Forged Engine closed deck conversion £7590

True, If spending I’m that kind of money anyway I may as well go forged.

Would the forged closed deck conversion be worth going for? I’m not after big power gains, But I guess it would be stronger and less potential problems later?

adam.pah

Mark has a good reputation and I believe is doing some of the RCM builds nowadays.
The good thing about having it done there is they will build AND map it.

Hawkeye D

Depending on mileage, you may want to factor in a tougher clutch - mine is an ACT and has been fine. I'm no launcher though.
I agree with above, full build with bottom end bearings replaced. I think ACL have stopped making them but I could be wrong. My bottom end bearings are now Mahle.

I had a nice 2.5 STi forged build after HG's, then 45k miles later it suffered a cracked cylinder liner. It would splutter on start up, white coolant smoke like you wouldn't believe. Then overnight so much coolant got into cylinder 1 that it just hydro-locked and wouldn't turn over with the key or manually with a bar and socket on the crank pulley.
Man that was a bad day I can tell you!

Gutted, but **** happens. Second build saw a brand new block, kept the standard crank and 45k miles Manley rods, rest was refreshed with new Mahle pistons as my old block was honed at first rebuild so old Mahle pistons were fine in terms of condition - but were a hair too big for my new block, ARP studs, Cosworth HG's and so on.

I'm on 342hp and 410 lb-ft

Something to be mindful of if you do forge it, you will most likely get fairly noisy piston slap when cold starting. Can sound awful on a cold morning, but it goes away once the pistons have expanded with heat and are a slightly tighter fit in the bores. All normal, harmless, and goes hand in hand with forged pistons, but can sound scary lol

NOSSY_89

How are you getting on mate.

I was at the garage the other day and bumped into the owner. I spoke to him a while back and we got talking about performance rebuilds and he mentioned he doesn't do performance cars anymore so didn't pass on his details to you. He used to build race engines and one of his N/A builds got the record for fastest in its JDM class. Anyway when I spoke to him I mentioned about your car and that it was a 2.5. He said while its out get it forged. He does loads of rebuilds and even did my Uncle's car. The original engine went bang due to dealership negligence and they threw so many excuses to get out of it. Any way this guy rebuilt it when every other garage said they wouldn't touch it and only option was to buy a new engine from the dealer. The engine was spot on after the rebuild.

The owner had a Range Rover in for a rebuild and I've seen merc, bmws etc there. I normally have a social chat with him so speak about cars, rebuilds etc. People who know me know how sociable I am lol.

Won't do that middle man business so if you're interested let me know and I'll pass his details on to you. Then you can speak to him about spec etc so he can price it all up. Plus he is in Brum.