Gents
I have just purchased a 2.5l sti ej257 short block and plan a complete conversion project over the next 6 months. I have read many posts on here.. and there are some good ones of people that have done such. My questions are that I could do with any advice that you could recommend that I perfrom in order to acheive a reliable 400Bhp with plenty of torque.

The base donor car is the following
1999 v5 wrx Sti
full H+S decat system
Std ECU (mapped for 2.0l engine mods)
front mount cooler
Induction Kit
Walbro Fuel Pump
FPR
td05 20g turbocharger
Stainless headers and turbo up pipe

I have read that I can utilise the standard components from the 2.0l engine with only the head gasket being different to that of the standard 2.0l setup is this correct. Such that std heads,cam belt cam pulleys etc are all usable for this conversion.

If i want reliable power levels like i have stated will the standard ej257 internals cope or should i change them while the engine is still only in short block form?

Will i also be alright for run -in purposes to run on the existing ecu map.

 

unsure on full detils but all ur heads cams etc deffo work on the new block ur std ecu will work but will need remapped with mods u ot id say u be lookign at around 360 bhp but dont quote me on that
its advisable to uprate ur pistons and head bolts once u start getting to the 400bhp mark hope this is of some help to u im sure will be some more people along soon with lot indepth info to help u out

 

You cant run in on the existing map, the 500cc extra is too big a change.

The 20g will prob make just short of 400bhp but will work well on a 2.5. However at that power level I would change the pistons as the standard on an EJ257 are not suppose to be very good. Rods will be fine up until about 450bhp.

 

Hi mate,

I'm doing the same build on my 2002 WRX, I'm hoping for about 400/450bhp with the following spec.

EJ257 Block
Manley forged pistons
Manley Con Rods
New Std Crankshaft
Uprated RCM oil pump
Manley performance valves
Brian Crower 272/272 cams
Brian Crower valve springs and retainers
EJ20 heads machined to match EJ257 block
New turbo (havent decided on which one yet)
APS Front mount intercooler
Kakumei GT Spec manifold
650cc or 700cc injectors (waiting advise on these)
Perrin Induction kit
Blitz Nur Spec R exhaust system
ARP Head Bolts 11mm
ACL race bearings
ECU remap or aftermarked ecu (havent decided yet)

Some other bits too, hope this is of some help to you.

hope your girlfreind is more understanding than mine though, shes fuming at the amount I have spent already, especiall when I told her it would only cost "a couple of hundred quid".... Come on, you have all done it!!

 

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What is the purpose of the machined heads to match the 2.5L block, are they a direct fit or arent they?

Also i have a standard wrx sti 5spd box can I expect reliability at the 400 mark with this box if it is maintained well.

 

I'm not 100% sure of the purpose of machining, I asked API Engines advice and they said machining would be better than just putting the ej20 heads straight on.

My standard 5 speed packed in when I was running a little over 350bhp, it had only done 18,000 miles, if your budget allows it go for a 6 speed, ive had no problems with mine, you can still use the 5 speed clutch and flywheel with it.

 

Arp head bolts and decent head gaskets should be added, also consider drop in pistons while the blocks out if you plan on making more power in the future, if not then your current list engine whise is fine.

As for gearbox, well it may or may not last very long. You will also need a good clutch, exedy paddle, or single plate or ATS.

Depeding on what your current injectors are and what you plan to replace with, may or may not allow you safe head room to run the car safley for the first 100 miles on actuator pressure with the exising map, however this should only be done to iron out any small build issues you may have, from this point you need the mapped tweaked for the loading process to begin.

 

Machined heads i assume would be opening up the chambers to match the 2.5 bore.

 

Mirror matching the cylinder head squish areas to the chamber bores is highly recommended. As burn rates can be greatly effected when running smaller sized heads on a 2.5 litre block and pre ignition/detonation often occurs. So by mirror matching the squish areas to the chamber bores the engine will have a better combustion and be less prone to detonation which can result in head gasket failures and damaged engine internals in the worst cases.

 

Thanks for explaining that bluerigster,

makes alot of sense, not sure what power increase the cams, valves, springs and retainers will bring either. I bought them because I assume they are stronger. Found out I need to add adjustable cam pulleys to the list now.

budget has been well and truly blown now!!