Just wondering if anyone has any solid information as to what power the standard WRX heads can take before cracking or needing valves, springs etc!!

Now i'm going for uprated internals for the 2.5 and the turbo is now a little bit small for working most efficiently, in the future i will be getting a bigger turbo. So! as the internals of the block can take a bit more stick what would be the sort of power the wrx heads (ported) could handle????

They were good at 380bhp and ok for 400bhp and probaly ok for the 430ish i will be running when mapped. I currently have a TD05/06 so when i change to a bigger turbo capable of around 500bhp, will the heads take it???? or shall i just get the bigger turbo and let it run more efficiently albeit at around 450ish, keep the same TD05/06, or pile more money into head work

Thanks
Scott

 

Personally no idea, but you may find this site interesting....

http://www.spdusa.com

Especially these pages

http://www.spdusa.com/new_page_4.htm

http://www.spdusa.com/high_power.htm

Just something I found surfing around, I have a 'New Age' Scoob too.

 

Some good points in there although i think their figures are a little pessimistic, i mean they are talking about an STI being seriously stressed at 350bhp

thanks
Scott

 

you will need head and cam changes to make that power easily/properly.

Sti head swap would be easiest and cheapest route, will take 8000rpm more reliably with underbucket shims, and offer better ignition timing due to sodium cooled exhaust valves.

Paul

 

Paul

Do you mean STI5 heads or STI7/8/ heads. Would the STI7 heads fit my car and work with my ecu???

Thanks
Scott

 

Either would be a step forward. You want the large port heads found on JDM sti 8/9-> and I think uk sti 7. They are also on the 99/00 sti.

Cams wise I think the latest spec C cams are quite wild for standard, but heads are going to be difficult to obtain. THe earlier heads with no AVCS is what John banks is using to good effect. THose coupled with adjustable cam pulleys will be a cood option I think.

Best thing is to see what you can find first.

Paul