Given that good STI AVCS heads are getting hardish to come by, I'm thinking about possibly getting some drop in cams instead for my WRX heads.

I already have a built bottom end which should be good for 8k RPM, but of course my current UK WRX heads would not be happy or effective at those RPMs. Maybe 8k is a stretch, but I'd at least want to see 7500 safely.

I'm only running a little hybrid TD04 at the moment, but at some point I might want to run a 400+ turbo, and it seems like 400 is hard to break with the normal WRX heads.

Positives for going for cams instead of complete STI heads are that there's no need to change headgaskets and AVCS wiring (I'm locked to ecutek unfortunately, so can't use the TGV wiring for AVCS control).

Negatives would be that maybe the heads have to come off to install tougher valve springs anyway? I know on some engines it's possible to change the springs without taking the head off, but not sure how easy that is on an EJ20.

Does anyone have a view of how much less efficient the actual WRX castings are compared to the STI castings?

 

Plenty of classic guys running over 400bhp mate. The main reason heads don't get talked about is because of the position, its always engine out. On other cars you can do it while the engine is sat in the car.

Having said that different cams offer different things, low down, top end etc. Try and match it to what turbo you want to run. If your turbo runs out of puff at 7k no point putting in 12k aggressive cams (over exaggeration but you get the idea). However going slightly more aggressive can change the feel of the car too. I've looked into it a bit but can't give much more information then that.

Some of the names that keep popping up are kelford cams and HKS but can't seem to find any for a 99 classic.

 

Are there really that many running 400+ on WRX cams? I thought the WRX cams were basically "over" at high 300s.

Nasioc seems to suggest one could run STI cams (AVCS) in the WRX heads and get the higher lift of the STI cams. It wouldn't spool any better than a WRX (because no AVCS), but at least top-end should be similar to STI if I understand correctly. E.g. https://forums.nasioc.com/forums/sho...s+in+wrx+heads


The installation looks like a bit of a nightmare, though, like you say

 

The classics didn't officially come with AVCS so would be a STI/WRX/Turbo 2000 cams, unless it hasn't been mentioned or I've missed it. Thats where I got my reasoning from.

But if you're at high 300s then a cam upgrade or porting might have better results you're better off speaking to Alyn. Like I said cams change the characteristics when going after market. Different inlet and outlet combinations.

 

Ah I've just realised, you're looking at more top end with a higher rev range. Higher lift cams will give that but I'm not sure on the exact combination but assume it would be easier because you aren't needing the low down spool