Absolute Shower

Okay can someone thats done the 2.5L mods etc help with a few questions i have please...

Whats the max bhp the oe 2.5L internals can handle - taking it that injectors, intercooler etc wouldn't be a factor.

What gaskets are best to use with big power figures...and what about the head bolts - whos best for those...

What sort of prices would you expect to buy the block and have it fitted?

Would oe MY02 WRX valves be a problem due to their size?

Mark A

iTrader: (1)

Have a read of John's & my threads, most of the answers can be found within them.

My own opinion is;

400bhp
Cometic or Standard gaskets
OEM or APR head bolts
£1100-1200 just for the short engine, fitting extra
I don't believe the valves would be a problem

Mark A

john banks

I'm trying mine at what I think is about 480 BHP and 440 lbft (certainly feels ridiculously faster than the old dyno tested 434 BHP and 395 lbft), its OK so far, but very early days. What I am seeing is encouraging. I am being very cautious with fuelling, timing and temperatures. The 740cc injectors are at 84% at 3.5 bar pressure, 11:1 AFR.

911

Bog standard short engine John?
Graham.

Adam M

I personally don't believe the short block will last a decent amount of time at that output.

Can't back it up, just a gut feeling. I hope to be proven wrong.

john banks

Yes, bog standard Graham. I wouldn't track it at that boost though

If not, I get a Crawford 2.33

Dyney

I'd go along with Mark's answers.

Over 1.4 bar and 400bhp has yet to be proven reliable

I expect your looking at £600+ for the swap depending on where you go and what else you do

tweenierob

Mine lasted for 6000miles at 500/450

Gut feeling is 420/420 max for std internals but this makes for a very very fast road car...

Other things need to be taken into consideration..... not all heads are suitable for the usdm 2.5 engine... and will not take timing or reap the CC increase benefits...

£1200 engine
OEM bolts
Oem gaskets


I will prob go this route again in the future but will be kept at 420ish of each

Rob

megrac

What heads would those be? phase 1 and 1.5? i've got ver3 sti heads with the new version na ej25 headgaskets on mine and find it takes good timing from 4.5k on but really dosn't like it from 3.5k to 4.5k. even at low boost of 10psi.

tweenierob

any work on the heads?

Rob

megrac

No. just a recon. if i had the engine apart again for some reson(witch i hope i don't) i would reshape the combustion chamber to look more like the phase 2 and to make them match the bore size.

tweenierob

I copied Pavlo's work as best i could remember on my own heads (phase one) my car, and two cars he did the heads on all take good timing throughout...

IMHO phase two Uk cams are a waste of time, even more so 2001 onwards (Heads are ****e).

Rob

megrac

i just don't like the look of that wobble combustion chamber shape in the phase 1 and 1.5 heads. i have no idea what uk heads are like as here in NZ we mostly only get jdm.

tweenierob

sorry should have read uk cams are no good IMHO rather than head design..

Phase two combustion chambers arent all they are cracked up to be IMO

My phase one heads worked very well on my car.... i changed the combustion chamber shape though..

Rob

megrac

you don't have any pics of them after you changed them do you. its all to late for my anyway they've been on the car for 1 year now. my ver3 sti cams should work ok.

tweenierob

I will try and find them, they are on a disc that i wrote before i formatted (along with 20 others)

My cams were similar to ver 3 STi it seems..

Rob

RS Grant

Surely the gearbox will give up at 400/400 though??

I am talking about a Phase 1.5 MY98 UK Gearbox... Would an STi/WRX 'box be any different??

The complete cost of the conversion is more like 4k though isnt it, as I was impressed with the initial £1200 figure I read about a wee while ago..


Cheers,
Grant

john banks

It will trash a UK gearbox in short order, unless it is a six speed IMHO. Some STi 5 speeds might be OK.

simbo

i am thinking about doing this convertion using 93 wrx heads what all do i need to do to these heads?
got tdo5/6 20 g
740 cc injectors
and ruuning apexi power fc


cheers david

tweenierob

Clutch, prob gearbox not long after...

Rob

DaveBlueRA

415Bhp and 427Bhp here at 1.3 Bar with a tractive effort on the rollers of 1800 lb/ft

And the standard box didnt last long at all, infact it blew up on the road test after the final mapping

Fulham71

MY my01 5 speed gear box seems to be holding up ok !

but I have gone a slightly different route with a smaller turbo hence less lag (none) & figures of about 350/350 !

Conrad@the Racing line

I think you mean tractive effort of 1800 lb's Dave

DaveBlueRA

Yep thats it

minty

iTrader: (1)

Dave was your box an RA as your name suggests ?? i am about to do a similar thing and am having serious thoughts about the gearbox strength in my RA. Are UK 6 Speed boxes stronger than RA ones then ????

P20SPD

iTrader: (1)

minty, yes they are, they are miles stronger.

I currently have my Uk 6 speed for sale.

tweenierob

You are able to fit it as well arent you P20SPD?

Rob

Conrad@the Racing line

6 speeds are rated at 550 ft/lb's The latest 6 speed on the MY05 car is aledgedly even stronger

jb2000

forester gearbox

DaveBlueRA

Yep it was the WRX RA box (the one without diff control). And after it had the final map done it went on the road test and obliterated 2nd gear. The option of a 6 speed was looked at but at the end of the day it is still a standard box so i went with a modena dog box