Currently Upgading my own car in (view my scoob), I am installing a forged 2.5l Bottom end and wondering if I should be thinking of upgrading to STI Heads or if the WRX heads would be o.k. or whether they will need some work I.e springs, Cams etc.

Am planning to keep the existing rev limit of 7200 rpm.

thanks

 

version three or four sti under bucket shimed heads are good ,

 

I would think the wrx heads you have would be ok for now.

 

Hi

I have a MY00 running more than 450bhp using the UK heads and a 2.5 bottom end. Only change was some porting and polishing.

Cheers

 

Is that with standard Cams, Valves?

 

ii may have some heads for sale in a few months ??? sti5 heads extensively poprted with wild cams !!

 

Sounds tempting but expensive, but need to pay for my PPG's before I can think about that, Was hoping to use standard heads for the moment.

PM me when they are ready for sale and I'll check the piggy bank.

 

anything that adds loads of power and torque to a big power car always is

 

why build it twice , do it once and be done . build it good and stong to last , also when mapped for uk heads will need mapping again for the next ones you put on so may as well spend now and get lump sorted first . if your thinking of a ppg kit speak to mark at lateral good price and helpful , thats where i got mine and its great .

 

Yes. Rev limit is also around 7000~ish. If you are not planning to go past 450-500bhp (don't know how much further the normal WRX heads will go but I know +-500 bhp is not unreasonable) and you don't need the extra revs provided by STI heads, I don't see the need to go for 'better' heads.

 

Cheers DesR, thanks for the advice.

 

I'm running over 470 bhp on my 2.5L with UK 2002 heads, wild piper cams, std springs...will go upto rev limit no probs (and it does, toooo easily lol).

 

Do you know What Duration them Cams are?

 

I would certainly go with uprated (over UK non sti) spec cams.

What heads have you got? That would be a good start.

 

The heads are standard UK WRX MY00. Was looking at getting some 264 duration cams with uprated springs and retainers, But If I can acheive my target figures 450/450, with what I have, then obviously will try that first.

 

I'm running 285's on mine but must admit I'd go for a lower profile if I had the choice again just because of the idle and very low speed cruise...still love it though put smile on my face all the time...which is what its all about.

 

I really like good head, ( 's )
It really makes it feel much better.

 

Don't bother trying for 450/450 with UK heads. Do the heads now and save a lot of work and/or money over doing them later. 264 cams ought to be about right, but it will also depend on the capacity of the engine.

 

Am I right in thinking that the head castings themselves are the same its just the valve train thats different.?

I have a spare set of UK heads and was gradually going to build them up with new valves, cams, retainers springs and spring seats and then just use the buckets from my STI Version 5 Heads once I take the current engine apart. Would apreciate your input here Paul.

Daz

 

correct. The valvetrain/cams is the difference. But that's the expensive bit to change.

 

Got my eye on your Supertec valves Paul. Plus I am liking the Kelford Cams deal for 272 10mm inlet and 272 10mm ex complete with double springs, titanium retainers and spring seats that I have seen else where for £895 + the dreaded.
These any good?
Daz

 

As I put up the top is a 2.5L build, Thanks for your advice, was also looking at these Kelford Cams, do you know if these are any good? they can be bought very cheap from NZ so was concerned at the quality.

So am I o.k to assume current valves are o.k or will I be looking at a potential failure?

 

Is this true of the phase 1 heads? Have a set of ported and polished phase 1 WRX heads, and in the process of aquiring some sti4 heads. Would it be possible to swap all of the good bits from the sti 4 heads into the ported/polished WRX heads, and would it be worth the trouble?
thanks
will

 

I have just put together a kit of parts of for early phase 1 heads. Springs, seats, retainers, shims, solid followers, stainless inlet valves, inconel exhaust valves. You will need to run solid follower profile cams though.

As for valves, I would always recommend uprating them, as they are so cheap to do in the face of how expensive a valve failure will be.

Paul

 

Not sure but we have springs and retainers that use the sti 5 style shims, not sure that kelford offer that setup.

 

Hi Paul

Interested in why you feel this way. Andy did the mapping for my car and while it hasnt been dyno'd he felt that it was running in the high 400's. I understand the benefits of running better cams in terms of improved performance, but from the perspective of getting the car to 450, I'm quite surprised you feel this isnt possible on UK heads (though mine are ported).

Cheers

 

I didn't say it wasn't possible, I think it's not worth doing. The small outlay of even just some sti heads make a worthwhile difference.

 

Have to agree with that, if your going to build/rebuild an engine then your going to be spending thousands and many hours doing so, why not just spend an extra few hundred on heads getting it right rather than going to all the trouble and money for the block and then thinking 'wish I'd done the heads at the same time'? Personally I'd saying if your rebuilding then do it right first time, as your going to have to spend a load of cash on the block/labour anyway.