silent running

I've done a search on this and can't find anything so it's time to get technical. I'm looking around at various v1-4 head options to go with my block once it's built, so seeing as it's virtually impossible to tell at a glance what version the heads are, I need some proper specs. This is what I know so far about heads, please correct me if I'm wrong and add any extra that you might know:

• Versions 1 and 2 had a square plug recess whereas v3-4 had a more oval shape.
• Versions 1-4 all had their inlet manifold bolt holes in a straight line, v5-6 were not.
• Early heads (i.e.v1 and 2) all used hydraulic tappets
• V3 & 4 STi heads used shims and some v4 WRX/Turbo heads used shims?
• The actual casting of the heads i.e. combustion chamber and ports was identical in all heads v1-4, regardless of whether STi, WRX or Turbo?
• The only difference between STi heads and standard was that they used sodium filled exhaust valves and lumpier cams, and on later versions, shims rather than hydraulic tappets.
• WRX cam lobe height was the same for both inlet and exhaust at 41.78-41.88 mm.

It appears that a head is basically unknown until you've got a cam off so you can look at the tappets properly. And even then, you could very easily end up with WRX 4 heads rather than STi 4? To tell the difference you'd need the cam lobe height which should be greater than the standard cams, but where are these specs? Are they secret or something? I can't find them anywhere.

Cheers!

Jolly Green Monster

iTrader: (4)

not all you have said is correct

some sti and sti ra had solid lifters in v1 and 2 but ti an extent it seems random with some having 7000rpm limit and other 7500 and therefore better heads and cams

the uk and wrx v3 and 4 solid lifters are over bucket shimmed and the sti v3 and 4 under bucket. under being better as once assembled the shim can't / shouldn't fall out as easily

some pics here of sti
Inlet manifold :: Fotopic.Net

the lift and duration is not really secret just no one really knows.. I measured what was I believe v4 uk cams and v3 sti some pics hear but I only crudely measured lift as it was all I had access to at the time
Cams :: Fotopic.Net

the best to fit a v1 to 4 car are said to be sti3 heads due to valves, shims and cam duration and lift and can be revved to 8k.

Simon

silent running

Helpful as always Simon, nice one. Well if I ever get an STi 3 or 4 head I'll measure it up too. It should be fairly straightforward to work out valve lift from base circle minus lobe height. Any identifying marks on the sodium filled exhaust valves off of STis?

Jolly Green Monster

iTrader: (4)

I have a 2 sets of sti3 heads if I ever get time I can measure one set, the other set is in use.

the set I am not using at the moment don't have standard valves in.. typically the set I am using do have standard valves, sorry not stripping it to check

Simon

silent running

Well I think I may have got hold of STi 3's but all I know at the moment from the photos is that they are definitely v3 or 4 and have a plain top to the tappet, meaning that they must have underbucket shims - if I interpret your words of wisdom correctly, v3 or 4 non-STi heads would have overbucket shims, which would be visible straight away. We'll see when they arrive I guess. Do you have a link to a PDF manual with the STi 3 or 4 head specs? I can get one for a v1-2 WRX, and a V7 WRX and STi, but nothing in between.

Jolly Green Monster

iTrader: (4)

no links sorry.. there used to be v3 manuals about but don't think it gave much head info

Simon

merlin24

iTrader: (1)

STi Version 3 + 4 Valves are stamped:
IH on the Inlets
EH on the exhausts.
Head Codes are LH-B and RH-B ( same casting as UK spec )
Valve Springs are colour coded White and approx.56mm in height.

Mick

silent running

Excellent, thanks. What are the standard WRX/Turbo valves (v3-4) stamped with, just out of interest?

merlin24

iTrader: (1)

ID2 on the Inlets
ED2 on the exhausts.