In the process of collecting parts for a 2.1 build . Got a closed deck block and i'm running a 2005 wrx at present .
Question is At what power will the wrx heads/cams start to struggle? And what other heads will fit my inlet manifold ? ie later classic sti 5/6 heads ?

 

Bit of an unknown in my experience, boxes tend to go first. Know of a few people running 400+ on standard internals.

 

Hard to say,what power would like to run?

WRX heads 2.5L have good flow on the 2.35 or 2.5L,I've seen them to run high 500bhp or 600bhp

For 2.1 I would go with STi AVCS heads,if you have ECU which can control AVCS,if its budget JDM big port AVCS heads will be best

If you want make yours heads best porting and polishing your heads with better cams,but price will be similar or greater than for JDM STi Big port heads

All depends on your target,we are running on our 2.1 JDM WRX heads not ported or polished and we are running 490bhp on V-power and 20% methanol

Jura

 

Thanks for the replies peeps !! so im think my spare set of v7 wrx uk heads should be ok as looking to go around 400-450hp . at present but you never know . Knowing me it wont be long and ill be collecting bits for 500+ lol to be fair this is a on going project and wont be built for a year or so as would like to get as much out of the standard motor as possible , Now just to decide on the turbo for the moment as mine is a poor quality
18g and does'nt perform well , so do i wait and get the big turbo say sc46 for the build? or go and buy a sc36 or 38 now and sell when i need the sc46?

 

Hi there

For 500bhp I wouldn't use your spare heads,I would go as I said with those heads UK STi heads or JDM STi "Big port" heads,those heads should work nicely on 2.1L or if you could source V6 STi heads which can be good option

About the turbo,we are went with MDX321T,which I can only recommend everyone and about the SC46,I would go down the road SC42 or SC46,those turbos should be good too on the 2.1L.Buy once turbo,is no point to buying twice turbo,you never know for how much will be turbo available here in the for sale section

Jura