blockhead

iTrader: (9)

Hi,I have a uk impreza 2000 turbo,normal spec really,I am building a 2.5 fully forged bottom end,which is built,now on to the heads,I have a option to use the standard impreza 2000 heads(vers.5) but I have a set of vers.3/4 sti heads all ready for the build,so I dont know which ones would be the best for me,as if I use the vers3/4 sti heads my inlet manifold wont fit.but I was wondering could I swop all my sensors,throttle body,auxilliries off my vers 5 to a vers3/4 inlet manifold,because all the wiring loom is different,will this work?also which heads would be the best for power wise as looking to go sumwhere around the 400bhp mark,the heads will be ported and polished which ever ones are going to be the best option.Thanks in advance for any input.Thanks Dan

Splitpin

It's difficult to provide you with a fully formed answer as you haven't given us all the info we'd ideally need.

However, stick with the 99/00MY UK head castings. They're better than the older ones anyway and avoid you the headache you'll volunteer for trying to adapt the older heads to the inlet manifold and control systems of your car.

Presumably you've already taken advice from someone as to whether the cams, standard valve springs and overbucket shim system will be suitable for the amount of power you're aiming at and the sort of rev limit you want to run.

blockhead

iTrader: (9)

Not really thought about that just thought the vers.3/4 sti heads are more flowing than my standard heads.keeping my heads would be the best solution,as you said save alot of hassle,but always thought the sti heads would be better for performance and flow,which would me on target for my bhp figures.

Splitpin

Don't know why you'd think that. 99/00 UK heads use the same castings as STi5/6, and that's before what you've just said about having them worked.

blockhead

iTrader: (9)

Do they really I didnt know that,so really there is no clear advantage for me using the vers3/4 heads over mine just alot of me wasting time and money.do the vers.3/4 heads have higher lobe cams to open the vavles further?Do the vers.3/4 heads have upgraded vavles or cams in anyway?thanks for your infoDan