joe v3sti

iTrader: (8)

So now I've finally got my act together and started with the engine fettle I'm after a little info on the version 3 Sti heads.

The build spec is

EJ257 Block
Wiseco pistons
K1 H-Beam Rods
STI Crank
ACL Race Bearings
Balanced Assembly
ARP Studs
RCM Oil Pump

Realistically this set up is good for up to 450bhp, so will the version 3 heads also be ok at this level?

I'll be having them fully stripped, chambers machined to suit the 2.5, valves laped, re shimmed, pretty much rebuilt. Will the valve train be up to a reliable 400-450bhp?

Is there anything else that I need to to the heads? Porting/polishing etc?
Cheers joe

mazmike

iTrader: (5)

ran 458 with no problem on a 2.1

RICHARD J

iTrader: (4)

They will be OK to about 450 but I'd fit a set of Supertech valves for peace of mind & to future proof it as if you want to go to 500 at a later date it's a big expense to strip it for a set of valves.

joe v3sti

iTrader: (8)

I did think about a set of valves, for future proofing. Obviously I wouldn't need uprated or double valve springs unless I used a hot cams would I ? What sort of power can the standard cams be run at?

With regards future proofing for over 500 Bhp. I would also need to get the block halves closed and ideally go 14mm head studs surely?

RICHARD J

iTrader: (4)

With the right mods the standard V3 STI heads & cams will go over 500 but there is a risk of valves cracking & wrecking your engine & turbo & that risk is greater over 450. You can take the risk & may get away with it, or you can replace the valves & then you don't need to worry about it. My V3 STI heads are at 460 on standard valves & I wish I'd replaced the valves last time the engine was out. I think you would need the CDB conversion & head stud conversion to go over 500 but it will end up costing a fortune.

banny sti

iTrader: (68)

I ran sti 3 heads at 523bhp but for peace of mind I would do the valves, however if you are regularly revving over 7.5k I would also look to do the valve springs too

328isport

iTrader: (6)

Re studs I'm sure I've read recently there are some 11mm studs available that are more than capable of 600bhp, and this was by someone who had real experience of this as had been running them for some time with no issues.

I'll try to find the thread and post it up. Would be less hassle than the 14mm conversion and from what others have said if you do the studs and valves from the outset, then your good to go in terms of future power hikes without having to open the engine back up

boosted

How long do you expect to get out of a set of bearing shells at that sort of elevated power level?

banny sti

iTrader: (68)

Cossie 260k 11mm studs will handle 600bhp

328isport

iTrader: (6)

That's them :-) I can't find the thread now but sure the car that i read about running these was either drag or time attack so not exactly used lightly

banny sti

iTrader: (68)

Clive (madhammer) runs them on his 9 sec drag car

Steve Whitehorn

iTrader: (13)

This
put supertech valves in
Stick with 11mm head studs.

Also be aware of ebayers passing of V3 WRX heads as STI ones

STI V4 s will also do the job. Rumour has it the cam profile might...might be slightly less aggresive. But I have never seen proof. I have run Sti V4 heads to 450hp

joe v3sti

iTrader: (8)

My version 3 Sti heads are currently down at engine tuner having a till strip down and rebuild including having the chambers machined to suit the 2.5. Last time I spoke with Alan he said all in all they were in great condition. So fingers crossed they will work well with my spec.

Joe

Steve Whitehorn

iTrader: (13)

You should have no problem - with your spec

joe v3sti

iTrader: (8)

Coupled with an sc46 it should make a nice road car, not crazy power but hopefully nice an reliable

Steve Whitehorn

iTrader: (13)

A 2.5 in a classic shell with those heads, turbo ect makes a really nice torquey car
I had one running 450/450.
If you want more power later - it is worth getting inserts into the SCD Block at this stage.
Depending on how it is being used.....
2.5s tend to run hotter oil temps than 2.0. So oil cooler is something to consider
Return to sump catch can? mixed views on those. But if it a little oil thirsty being a 2.5 worth considering.
Guess you will be running a six speed box. They tend to restrict the airflow as subaru intended out of the engine bay area...so also an area to watch
Just a few passing thoughts...anyway good luck with it. It will be an awesome road car

Steve Whitehorn

iTrader: (13)

Personaly for RELIABILITY if sticking with the semi closed deck block I would get it mapped to about 420. Everyone will have their own figures views. Thats mine

joe v3sti

iTrader: (8)

Some sound advice there, cheers Steve.
There's a bit more about the car here

https://www.scoobynet.com/sin-bin-424/963291-v2-sti-type-ra-not-quite-standard.html