MadUsa1

The head gaskets need replacing on my 2.5L hawk eye STI, after 33k miles of road and occassional track use.

I have been advised to have the bottom end rebuilt at the same time because apparently the bottom end tends to go soon after the HG is replaced.

Does this make sense or should I just go for the HG replacement?

I plan to have the car mapped for about 330 / 330 on standard turbo, exhaust and intake.

Alan Jeffery

I would always advise that it's a viable option, especially with a 2.5.
Most of the work is getting it to the short block stage, so it isn't a killer to say "the hell with it" and just keep going!
Being fair, the power figures you seek wouldn't normally trouble it, but the fact of it being bare in front of you helps the decision making process.

MadUsa1

Thanks for the reply, I fully understand the whole "while the engine is out" thing, but there's a fairly massive price difference between a stock HG replacement and a full forged re-build.

I've been quoted about £1400 for a hg replacement with cosworth gaskets and ARP studs.

A full re-build with forged pistons, race bearings (but standard crank and rods) will come in at around £3400.

Has anyone ever heard of a bottom end going on a 2.5L engine running 330 brake???

birchy2010

iTrader: (12)

Worth a read

https://www.scoobynet.com/scoobynet-...-failures.html

All about risk reduction.

MadUsa1

yeah, I've seen that post but I assumed the later 2008+ engines were simply weaker than the 2006 engines, is that not the case?

birchy2010

iTrader: (12)

i personally know of 2 WRX 2.5's that have failed when in standard form so doesnt appear so

ditchmyster

iTrader: (7)

another 2k is a bit steep considering it has not failed, so no modine no oil pump, what miles, is it close to cambelt and water pump time, i would shop around if i were you, ok maybe wise to replace all these parts while it's out but as i have discovered ther is a lot of sh1te talked about these cars, and if your staying close to standard it's not necessary to go the whole hog, and there are still no guarantees if you do.

DantheMan2605

Sorry to hijack,

MY 06 sti is at 47k, never tracked, just fast road use. Seems like my HG is going too. (black sludgey coolant, drinking more and more oil, rad cap overspilling coolant, rad fans come on quite a lot when not moving, even when ive been off boost.) I flushed the coolant and it returned after around 600 miles.

Ive had many HG tests carried out all have come back negative, ive have been told the rad hoses are breaking down, the oil cooler has split etc... Fed up of not getting to the bottom off it. Ive taken it off the road for now, and will be going for silicone hoses and a rebuild, seeing as the engine will be out for gaskets i will be upgrading pistons, rods, bearings, oil pump, oil cooler, etc...

My not so near future aspirations are around 400-450. So it makes sense that whilst the engine is out to have it done (or at least inspected in your case). The last thing you want is to do is have it out twice, even if you are looking for a lower power figure, you never know what trouble the 2.5 will throw at you next. Especially with their history.

Good luck, Dan

alcazar

iTrader: (2)

But what you have quoted is for fully forged? yes?

Yet you started out by saying replace bottom end? To me that just means bearings.

Get a quote for that, see how it goes, it's only usually the bearings that cause trouble after a HG replacement.

Midlife......

iTrader: (2)

I'd be tempted to stick in some better pistons like Mahle Powerpak to hopefully prevent ringland failure and take it from there.......

Shaun

MadUsa1

Thanks for the feedback guys.

I have decided to go with just the HG replacement at this stage. This will cost £1250 including the cosworth gaskets, ARP 11mm head studs and a head re-fresh plus all ancillaries and labour.

The alternative would've been something like £4300 for a forged engine with nitrided crank, uprated rods and forged pistons.

I don't plan to run much more than 330 bhp for the next couple of years so no need to throw the extra £3k at the engine at this stage.

Besides, since the weak spot on the 2.5's is the HG, seems a bit pointless spending so much money strengthening every other area of the engine.

I may well have to eat my words if I get a nice fat bottom end failure in a few months, but that's a risk I will have to take.

happydude303

iTrader: (1)

you could by a forged lump of some one on here for 1500 quid second hand

MOTORS S GT

iTrader: (2)

I'm with Alan on this. i would not take on a 2.5 head gasket issue with 33k on the clock without a look at pistons & bigends, on a 2.5, it has enough mileage to suffer ringland issues already, as already said with engine out & heads off your only looking at another hour to check it out, at worst to clean,rebuild with seals etc, 4 hours labour if everything is ok.