i-Club - The Ultimate Subaru Resource - We don't need no VTEC (...AVCS, ahem...)

As some of you may know, I have a true frankenstein motor in my car. I am using a fully built EJ22T stroked to 2.4L with fully built JDM AVCS heads. The heads I am using are non-STi AVCS, but it didn't matter to me if they were STi, since I swapped out all the internals for custom components anyways.

Here are some facts about the head differences. (USDM WRX vs. JDM AVCS).

1. Both STi and non-STi JDM heads have larger intake and exhaust ports than US WRX head.

2. Both STi and non-STi JDM heads have bigger valves than US WRX head. (The STi exhaust valves are .5mm larger than the non-STI ones)

3. Both JDM heads have shim-under bucket valvetrain (higher redline potential)

Thats what is most important. In my non-STi AVCS heads, I am using:

Axis Power Tuning: dual valve springs, Ti retainers, buckets, shims.
STi: Spec C camshafts.

So, I have head that is "more built" than the STi AVCS head, less .5mm on the exhaust valve diameter difference.

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I am using TEC III as a 100% standalone ECU, and I din't want to bother trying to hook up the AVCS, since it seems like it will take too much efford for little gain. So I ran with AVCS not connected. I have read that it was ok to run like that. I would just loose bottom end but gain mad top end. However, after the initial dyno runs, I saw that the power was falling off drastically after 7,000RP. Since my redline is set at 9,000RPM (will be 9,500RPM later on), I had to fugure out what was going on. Everything on the car is "top end power" parts. Huge turbo, huge exhaust, big motor, high redline.

So, after I spoke with Ron at Axis Power Tuning, he told that that "disconnected" AVCS was the cause of that. The intake valve timing was waaaaaaaay off causing the motor to choke up top. So, I had to do something about it. Ron breifed me on installing regular WRX cam sprokets onto the AVCS heads. I thought it was impossible, but I was wrong. It is actually pretty simple. I did it on my car in 3 hours total. That includes taking the timing belt off and putting it back on.

Apperantly the JDM AVCS head is not all that diff. READ: USDM STi HEADS ARE!!! The cams are pretty much the same shape. So is the actual head casting. But, the intake cams have 4 little holes on them that feed the AVCS cam sproket. So, all I had to do is to plug those holes so that the oil won't leak from behind the regular WRX cam sproket. Pretty simple, but scary, since I had to put a tap though the cams. ;) Never thought I would ever do that.

Here is what you need to do what I have described above:

L + R WRX intake cam sprokets
L + R WRX intake cam sproket bolts (The AVCS bolts are longer and have a hole in the middle ;) )
10-32 tap
Tap oil
Big ass magnet (if you do it when the heads are on the car)
8 10-32 SS set screws (short ones ~ 5mm)
Loctite
RTV
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You need to get the AVCS cam sprokets off. Then tap the 4 little holes. Then "plug" them with set screws. Use plenty of Loctite. Then RTV them over. Install the WRX sprokets. Done.

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What are the benefits? Well, I didn't want to connect the AVCS, since I don't care that much for few HP on bottom end. My 2.4L motor will take care of that. Also, as I found out, running with AVCS disconnected will make you loose power. And, I saved 1.8kg in rotating mass. The AVCS pulleys weight in at 2.8kg combined vs. 1.4kg for the regular ones. Pretty cool. ;)

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Why should you care about this? Well, because it is easy to by some nice JDM STi heads for about ~$800-$1400. And, for that, you will get a much better head with larger ports, better and bigger valves, shims under buckets, better springs and spicy STi cam. So, this is a good option for those WRX owners who want a better head for little $, since porting, new springs, new cams, etc for the US WRX head will cost a lot more than that.

Here are the pics:

Feel free to ask me questions, and yes, I am crazy... and "I ANTI JUICE..."