Pramas

well the time is coming, in around 1-2 month i wish to go forged route for my bottom end. Currently iam running a 2.5l hawk STi and its absolutley fine but i wish to aim for around 500-550.
My question is, do i stay 2.5 and pin or get the deck closed like bob did or try the 2.1 stroker route? ( will a 2.0 bottom end fit my heads? )
Also the car will be used as a daily driver so the extra torque from the 2.5 is nice.
All the required aux will be in place whichever route i decide to go, so is the 2.5 block up to the job or am i better off starting over with 2.0 block, iam looking around 5k to spend on the bottom end

BlueBugEye

iTrader: (12)

You should consider pinning or closing the block for those levels if staying 2.5, probably also looking at a valve train upgrade.

GezP

iTrader: (23)

You defo need to pin the block mate. I've just done my rebuild on a 2.5 and I was very happy with Pauls work at finch Motorsport. He did all my boring pinning and skimming, have a look at my build thread mate, shows all his nice handiwork.

Personally I like the 2.5 as I do love the torque. I don't think you'll have an issue getting 500 if you get the right parts etc.

IainMilford

iTrader: (15)

where is your thread gez?

GezP

iTrader: (23)

https://www.scoobynet.com/projects-4...-bit-more.html

In the projects section mate. Give me a shout if you've got any questions

stevie1982

iTrader: (16)

So that's 5k just for the removal, forging and reftiting the block? Also factor in the strip down after 1k to make sure the liners have sunk in ok. I would give a few tuners a call and see what they have to say. Going over 500 in a 2.5 can be very expensive so it help speaking to them for some friendly advise. David at API would get my vote but that's just my opinion.

Can I ask why 500-550 are you looking to hit competitions etc or more a who has a bigger member contest as from my experiance 450/480 can he had on a forged 2.5 and makes one hell of a road and occasional track day car. And a lot less cash to, do you really need 500+ is it just a figure in mind or a proper solid reason for wanting it.

Don't forget running something that high I would imagine will cost more to keep it all up and running so once you have got it can you afford to keep it, not knocking your financial position as its none of my business but its food for thought.

Good luck as a Hawkeye is next on my list so will be interested to see whic way you go and why.

All the best

jura11

iTrader: (7)

Hi there personally i would go with 2.1 stroker or if you find cheaper EJ22T block and build 2.35.

2.5L is great engine day to day driving,but its not revy as 2.1 or 2.35.

At 500-550bhp you will looking for standard or rotated setup?

If you are looking for standard location turbo,its possible via MDX321V with splash of meth,if you are not looking for methanol,option will be rotated GT30/63AR


Jura

LegacySTi

iTrader: (13)

2.1 on jdm avcs heads. if aiming 550bhp.

but if staying 2.5 defo pin and go 14mm head studs. upto 500bhp

APIDavid

iTrader: (4)

A 2.5 is going to be working really hard at 500 - 550 and will not last more than about 20,000 miles in my experience pinned or not.

There are various 'solutions ' being offered for making a 2.5 reliable at high power, Pinning and retro closed decking etc. I am yet to be convinced by them as a long term fix.

For safety, durability and length of life, I'd go 2.1 stroker. 2.5 seems Ok at up to 480 or so. So stick below 500 on a 2.5, or think again is my recommendation

David APi

Kwik

iTrader: (10)

There's a few 2.0l Closed deck blocks on here for around £300-450. The CDB is considered the stronger engine's so i'd go with that and you're still able to use your car whilst the build is going. There's a lot of 2.1 stroker kits out there.

Although i'm not sure what parts you'd be looking at getting outside of the internal's to make 500BHP. V3 STI Heads are also available on here for around £300-400.

Pramas

Thanks for that David, the 500 is more just a figure i have in my head, car will get occasional track day once all sorted so perhaps 480 is more relistic if i stay with 2.5.
Ive seen some cosworth 2.6 and 2.7 stroker engines about, how do these perform in real life and are these also rated to aprrox 480?

ALi-B

iTrader: (1)

Having seen liner failures on pinned 2.5s. I'd be inclined to agree. Not sure if the cuase of the liner failures is a metallurgy problem (i.e different expansion rates around the liner and thermal contraction/expansion stresses created by the pins preventing movement), or just simply running too much power.

Its probably the latter as IMO pinning it doesn't fully address the weak/thin spot where the crankcase bolts pass through - and guess where many crack! However pinning it does help brace the liners from moving round, which facilitates the headgasket sealing, but thats only curing half the problem IMO.

Anyway, how many miles would you expect to get out of a 500bhp 2.0 or 2.1 before it needs a routine rebuild? Assuming its tracked once every few months?

APIDavid

iTrader: (4)

None of them are going to do more than 20,000 miles before they need a freshen up. It is 2.5 times above original design engine power.................and twice STI power.

It is just that a 2.5 is more likely to scatter itself.

David

New_scooby_04

iTrader: (4)

I have one of David's forged 2.5s with an SC46 ; that'll get you into the right side of the mid 400s of each

For a road car, I'd argue you'll struggle to find a better set up!

Goes like stink, picks up from low revs and has torque everywhere.

If you really must have 500bhp+ then 2.35 if you're feeling flush. 2.1 if not!

New_scooby_04

iTrader: (4)

It's surprising how few tuners will volunteer this info IMO!

Hammer man

iTrader: (25)

I`ve got one of those too......






















but twin-scroll

MadUsa1

I was looking at the same decision a few weeks ago - I was about to drop 6-7k on a fully forged 2.5L, when I realised it would cost me less to trade up to a fundamentally superior JDM car of the same age and mileage.

Any concerns I had about lag, throttle response and low end torque went out of the window the moment I put my foot down in my new Spec C. The 2.5L is a nice engine, but it's lazy and laggy compared to the twin scroll JDM stuff. The spread of power and torque in the JDM 2.0 is far superior too, thanks to that 8000 red line.

The 2.0 in the JDM is good for well over 400 of each and you get alllllll the other goodies thrown in for free: quicker rack, roof scoop, oil cooler, 140kg lighter... etc etc

And then there's the depreciation: when you sell your current STI, you'll never get back the money you dropped on the re-build, even if it was carried out by a reputable engine builder. The JDM should hold its value far far better, especially since the current weak pound has effectively stopped the grey importers from bringing in new cars from Japan.

So, spend less money, get a far better car.

Tidgy

first question is, why do you need 500? on the road 450+ you will find it becomes a right handfull on a dry day, let alone a wet one.

Best bet is to choose a specialist you want to use to build it and discuss requirments, spec etc with them, setting an x target figure might not provide you with a car you are happy with.

stealthy55

might be in a classic......