I am aware of the issue with 2.5 STi newage HG however what I wanted to know is a car that has had a HG done back to factory spec (by Subaru just the HG not forged or anything) whats to stop it let letting go again ?

Cheers
Raf

 

If done by subaru nothing, and its recommended to do the crank bearings when HG fails on a 2.5.

 

As stated, always worth checking the bearings and replacing. that and the pistons (ringland failure is also common)

 

As said above, needs at least the bearings doing to avoid later issues.

 

Nothing to stop it going again had mine done under warranty and it failed again within 30k miles

I have now saved the £3700 needed to sort it out properly FORGED

I expect subaru only did the bare minimum e.g gaskets, probably didn't bother with head skimming or even check never mind replace bearings

 

as above on the 2.5 crank bearings need doing too but subaru won't do them , uprated hg gasket important plus head studs not bolts or the same thing is likely to happen again , even when all of that is done it still some times goes wrong , and then it's forged time

 

Had mine go at 32,000 miles and it's on it's way again at 68,000 miles, i had ARP bolts fitted when it went the first time, going to forge it this time and hopefully put it to bed for good.

 

what's going wrong with yours at the moment and what was done at 32,000

 

Headgasket is on it's way out again, i had a leaking radiator last year so had it replaced with a Mishimoto one. After it had been fitted i kept noticing coolant was leaking out of the overflow pipe on the top of the radiator so took it back to the main dealers who'd fitted the rad. When they tested it they found the coolant system was being pressurised under boost which is exactly the same symptoms as the first time it went. When i had it replaced the first time i had head skimmed, ARP bolts and steel headgasket fitted.

 

have u changed the pressured expansion tank cap for a 1.3 bar one , my cap was failing and i thought hg was going and it was not

 

It's not coming from the cap mate, it's leaking from the small black pipe on top of the rad where it joins to the fitting, i've fitted 2 small jubilee clips for now to stop it, it'll have to do till i get it rebuilt.

 

sorry just clarifying , the pressured expansion tank has a pipe coming out of the top of the tank , the flow to that pipe is controlled by the expansion tank cap spring as pressure builds then the coolant flows out to non pressured tank if the pressured cap spring is weak too much coolant flow but it may not be your issue

 

Struggling to see how a forged engine is going to stop head gaskets going?
Closing the block deck or pinning it, cosworth or rcm gaskets and uprated head studs yes.

 

the forged will just help the bottom end , as you say better gaskets and head bolts are the way forward

 

The block is what flexes and causes fretting of the hg and failure that way, rods and pistons won't help block deck stability.

 

Only over a certain power levels. 2.5 blocks will run 450bhp if built right for a long time even in open deck format.

Tuners have been doing them for years to that power level with no issues.

 

i heard the warning up and cooling down process is where the gaskets move between block and head , funny the 2.5 is more prone than the 2 litre as apart from bigger pistons the set up is pretty similar with a few changes for certain models

 

The steel liners are a lot thinner on the 2.5's

 

As boosted said, the liners on a 2.5 are pretty thin.

There doesn't seem to be a hard a fast rule as to why they fail. I hear various things blamed for it, but you see cars that have been babied failed and those that have been ragged to death not.

Just seems to be pot luck.

 

Pin it and stud it! Then boost the **** out it!

 

hehe, I went the closed deck converted route

 

I pinned mine because it was free to do. Pinned 2.5 block cost £200. 👍

 

cheap as

 

Engine was out an NA legacy, turbo/non turbo all the same ****.

 

ah right, my old engine was fooked (2.0) taper ont eh cylinders so ended up with a block out of a hatch sti iirc although as said closed deck converted

 

2.5 is way better for 400-450hp road car

 

plan is 550 hence the closed decking, but that's a way off yet due to budget limitations

 

is that with 14mm headstuds?
Trev

 

you about to link the thread about 2.5 heads and 14mm stud conversion?

lol

v5 heads