Is anyone running a set of STi3/4 heads with dh22 Kent cams on a 2.5 litre block and if so what is the maximum RPM these rev to?. As I've been running with V2 RA heads and they run out of puff very early around 5800 rpm. So due to head gasket failure, I'm looking at changing the heads and thinking of using Sti4 heads with DH22 Kent cams ported and flowed or going all out and purchasing Cosworth cylinder heads from Powerstation. Is anyone using any other type of cams and find them better?.

 

You'd need to change the inlet manifold i think, to suit the STi3/4 heads.

I'd be looking more at the turbo side of things, rather than the cams.

What turbo are you running at the moment and at what boost?

If your really determind to go all out in the cam side of things, i doubt you can go far wrong, speaking to Olly at RCM...

 

I'm porting my heads, have a few around so going to make the best I have with what I've got, retaining the shims and solid lifters

Agreed on the turbo side, thats sorted, GT35 Rotated, and rotated inlet the rest depends on the wallet, as it soon adds up with rods, pistons etc

also runing the '95 RA heads.

 

Hi I'm running TD05 20g which is running 1.2 - 1.4 bar with inlet manifold in original postion, spools up really well and starts pulling hard between 3500 to 5000 rpm then it's really flat and I'm changing up gear. Ideally want to make the engine to rev more like a 2.0I and pull up to around 7000 rpm.

 

Maybe the difference really is in what 500 said then, as i had no troubles with the car losing power above 5k with the 20G.

If your heads aren't ported, then i'd gave that a try before spendin **** loads on cams etc.

 

Sti 3/4 heads work well, and are good for 450bhp, + some.

The DH22 cam profile is very good, but they won't make a turbo flow more air than it's capable of.

People forget that the 2.5lt is 25% bigger, and trying to fill the bigger bores at high RPM isn't just about big cams, but having a turbo capable of flowing enough air at high RPM.

You will always have a problem getting your peak power at high RPM on a 2.5lt, unless you run a big turbo. Or a small turbo, at very low boost

Taking the 20G as an example, it's capable of circa 380-400bhp. A 2.5lt engine will make 380-400bhp at much lower rpm that the 2.0lt, say around 5500rpm, depending on boost, mapping, etc'.

So you get to 380-400bhp @ 5500rpm, and the turbo has nothing more to give.

The GT35R is fine, if you want 550bhp.


Mark.

 

BTW no need to change inlet manifold, the bolt patterns are the same on all My93-98 heads

 

Does this mean that an all out TD06 would be more suited to a 2.5 if you want power above 5500. I'm not really to bothored about a little extra lag but want as much power as posible without going rotated.

I know garrets will be better but they involve up-pipe, downpipe replacement which dramatically increase costs.

Craig

 

The MD321T seems to be an excellent choice for the 2.5 engine at the moment

Banny

 

This is one of Lateral's hybrids isn't it.

Does anyone know:

What turbo is it based on?
Does it bolt on in the standard mounting points?
How much do they cost?

Craig
(P.S Sorry if i'm hijackin, just very interested in 2.5 info - as i know weve strayed away from info on heads)

 

It is a Lateral turbo

What turbo is it based on? Garrett with an IHI exhaust housing
Does it bolt on in the standard mounting points? Yes mounts in the standard postion
How much do they cost? Best speaking to Mark at Lateral

Banny

 

Cheers.

Craig
(Hijack Over )

 

i am going to be using some STI5 heads/cams on my 2.5 to help it breathe better but in addition to that they will be ported and flowed and hopefully if funds allow some adjustible cam pulleys will be used, as i have been advised that very good gains can be had from this combination of mods. Not cheap, but apparently very effective....

 

ditto.

 

I've purchased a set of Sti V3 cylinder heads and now plan to have the chambers opened out to suit the 2.5l block. Can anyone recommend a place to have this done?, Ideally not costing too much.