I recently rebuilt my hybrid block, which is what I bought the car with. So, my knowledge of compatability when doing the initial hybrid build is limited. However, I thought this info might help someone. I'll include some pics, info I picked up along the way, and a pricing guide so you know what to expect when doing your build and also so there isn't too much time wasted waiting for parts you didn't know you needed.
First off, all the vacuum stuff is going to basically be the same if you are keeping your EJ20 heads, so label EVERYTHING! ON BOTH ENDS! I spent hours trying to wiggle stuff into place. I thought I labeled everything, and I still had about 20 misc. hoses, bolts, and brackets without homes that weren't fun to try to piece together. Vacuum routing is hard to get diagnosed over the internet, so make sure you take care of yourself on this.
The guides------------------------------------------------------------------------------------
This is the teardown of the block-
Tearing down a block - A pictorial. Includes head removal. - NASIOC
Teardown and build-
Engine Building: EJ251 with STI Rods/Pistons and head work - NASIOC
And the Subaru tech manuals of course-
Impreza Manuals | ken-gilbert.com
I also got some STI specs somewhere that were helpful. I could attatch them all, or email them if you need. PM me if needed.
----------------------------------------------------------------------------
Prices-
$150-$200 misc small expenses. Acc. Belts, Oil, Filter, hoses, clamps, rags, lubes, sealants
$65- Replacement elbow between Turbo and IC, broke it. Subaru wants $275. I went to Napa and got an aftermarket one for $65.
$98- Injector flow testing and cleaning.
$52- Back pieces of timing belt cover. Plan on buying these from Subaru, they break easy
$80- .051" Cometic head gasket. It was $120 cheaper than anywhere else on ebay, so I took the risk. I did it a few other times too.
$300- CP forged pictons. Part #SC7420. Good luck finding that deal, expect to pay $500-$600 new. I got mine off of Lil Shoaf (THANKS!) here.
$382- Head rebuild, Valve grind, Pressure test, resurface, helicoils, valve adejust, seals. All done at Cylinder Head Specialties in Portland. Awesome people and shop.
$100- Hot tank, clean, inspect and Hone block at CHS.
$30- Polish crank at CHS
$150- Exedy OEM clutch kit on ebay. Look around, they still go for that.
$140- ARP head studs from private seller on ebay. Expect to pay $200. BUT USE THEM! I got into the block and found the last owner used them, so I still have them new in box, for sale PM me.
$50- Piston rings, OEM on ebay. They wanted well over $150 at Subaru I think.
$100- Gates Racing timing belt at Racing products and high performance auto parts | Gates Corporation.
$267- Gasket and Seal kit. You need this! Part #10105AA590. $302 at Subaru. I got form a dealership selling on ebay.
$83- Cosworth Main bearings, same seller on ebay
$65- Cosworth Rod bearings, same seller on ebay
Other parts - You'll need another cam seal for the WRX heads. The gasket kit has one of the same size, and one of another for the STI heads. The seal was about $20 I believe.
At least around $10 and several trips replacing bolts that broke/stripped.
----------------------------------------------------
Misc info-
Look up the info about how to seperate the transmission and the engine. With a 10mm bolt, you have to thread a pin that releases the clutch fork. We pryed them apart for hours and destroyed my pressure plate and scarred up the bell housing.
Take out the exhaust O2 sensor before pulling the block. It's hard to take out, but it can get mangled being down low and sticking out during the removal.
There is a metal nipple that is on the STI block, by the block seam toward the bell housing. It is not used with WRX heads. Cap it off or rout it into the driver side vac system with a T. I just saved you like 3 months worth of headaches. That took me forever to get that info. It's pic 5.
You are going to have some small lips on the end of the oil rings. They didn't put notches for these in the CP pistons. Clip the little teeth-lips off and file them down. Pic 3
Doing the wrist pins- I used a long piece of 10 guage ground wire and made a hook that I hammered over tight. Worked great for pulling the pins. I also bought a LOOONG flat head cabinet driver. That was great for pushing them from the back.
First off, all the vacuum stuff is going to basically be the same if you are keeping your EJ20 heads, so label EVERYTHING! ON BOTH ENDS! I spent hours trying to wiggle stuff into place. I thought I labeled everything, and I still had about 20 misc. hoses, bolts, and brackets without homes that weren't fun to try to piece together. Vacuum routing is hard to get diagnosed over the internet, so make sure you take care of yourself on this.
The guides------------------------------------------------------------------------------------
This is the teardown of the block-
Tearing down a block - A pictorial. Includes head removal. - NASIOC
Teardown and build-
Engine Building: EJ251 with STI Rods/Pistons and head work - NASIOC
And the Subaru tech manuals of course-
Impreza Manuals | ken-gilbert.com
I also got some STI specs somewhere that were helpful. I could attatch them all, or email them if you need. PM me if needed.
----------------------------------------------------------------------------
Prices-
$150-$200 misc small expenses. Acc. Belts, Oil, Filter, hoses, clamps, rags, lubes, sealants
$65- Replacement elbow between Turbo and IC, broke it. Subaru wants $275. I went to Napa and got an aftermarket one for $65.
$98- Injector flow testing and cleaning.
$52- Back pieces of timing belt cover. Plan on buying these from Subaru, they break easy
$80- .051" Cometic head gasket. It was $120 cheaper than anywhere else on ebay, so I took the risk. I did it a few other times too.
$300- CP forged pictons. Part #SC7420. Good luck finding that deal, expect to pay $500-$600 new. I got mine off of Lil Shoaf (THANKS!) here.
$382- Head rebuild, Valve grind, Pressure test, resurface, helicoils, valve adejust, seals. All done at Cylinder Head Specialties in Portland. Awesome people and shop.
$100- Hot tank, clean, inspect and Hone block at CHS.
$30- Polish crank at CHS
$150- Exedy OEM clutch kit on ebay. Look around, they still go for that.
$140- ARP head studs from private seller on ebay. Expect to pay $200. BUT USE THEM! I got into the block and found the last owner used them, so I still have them new in box, for sale PM me.
$50- Piston rings, OEM on ebay. They wanted well over $150 at Subaru I think.
$100- Gates Racing timing belt at Racing products and high performance auto parts | Gates Corporation.
$267- Gasket and Seal kit. You need this! Part #10105AA590. $302 at Subaru. I got form a dealership selling on ebay.
$83- Cosworth Main bearings, same seller on ebay
$65- Cosworth Rod bearings, same seller on ebay
Other parts - You'll need another cam seal for the WRX heads. The gasket kit has one of the same size, and one of another for the STI heads. The seal was about $20 I believe.
At least around $10 and several trips replacing bolts that broke/stripped.
----------------------------------------------------
Misc info-
Look up the info about how to seperate the transmission and the engine. With a 10mm bolt, you have to thread a pin that releases the clutch fork. We pryed them apart for hours and destroyed my pressure plate and scarred up the bell housing.
Take out the exhaust O2 sensor before pulling the block. It's hard to take out, but it can get mangled being down low and sticking out during the removal.
There is a metal nipple that is on the STI block, by the block seam toward the bell housing. It is not used with WRX heads. Cap it off or rout it into the driver side vac system with a T. I just saved you like 3 months worth of headaches. That took me forever to get that info. It's pic 5.
You are going to have some small lips on the end of the oil rings. They didn't put notches for these in the CP pistons. Clip the little teeth-lips off and file them down. Pic 3
Doing the wrist pins- I used a long piece of 10 guage ground wire and made a hook that I hammered over tight. Worked great for pulling the pins. I also bought a LOOONG flat head cabinet driver. That was great for pushing them from the back.