The DOHC installation 'unspoken' details thread

[Legacy777]

Good info! Thanks for sharing.

[cj91legss]

So What are us DOHC guys looking at as far as a compression ratio?

[mike-tracy]

So What are us DOHC guys looking at as far as a compression ratio?

I've referred to this link on occation:

http://bbs.legacycentral.org/viewtopic.php?t=41519url

I haven't done the math on those setups so I wouldn't say they're accurate until I did, but they are prob reasonably close

[fasterthanyou]

On ej25d heads, For the egr port on the back of the left hand head, its an m16x1.5, I found that an 10+ legacy 2.5 drain plug fits this perfectly.

i just put a ball bearing in there and the stock egr bolt . and cut the pipe to the intake in half and throwed it away, ahaha

[James614]

Has anyone verified that an EJ25D timing belt is the same as the EJ20G?

[cj91legss]

Yes

[mike-tracy]

Has anyone verified that an EJ25D timing belt is the same as the EJ20G?

That's what I'm using. I don't have a hybrid block like CJ, just a straight 20g

[James614]

I was comparing timing belts online and found that the 25D and EJ205 both use an 88.5" timing belt with 281 teeth. So I went ahead and ordered the Gates racing timing belt for the USDM WRX for my EJ20G. I'm sure its the same.

[cj91legss]

Calling my block a hybrid is insulting >:-/ its not a prius mike!

Sent from my SGH-T989 using Tapatalk 2

[Legacy777]

Hybrid can be good....meaning best of multiple things. I consider my gauge cluster a UK hybrid cluster

[station2stattion]

I wanted to let the owner of this thread know that I have copied this thread to NASIOC.

I have given you full credit and noted that I have copied this thread. I found this info to be SUPER helpful to me and I wanted to make sure that it was always available.

If this is an issue, please let me know!

Thank you again for your work on this!

[Legacy777]

Can you please provide the link to Nasioc thread for reference purposes.

Thanks

[LilLegacy]

So compatibility wise, is this everything I would need for a dohc swap with a 22t block and 20g heads?

-Parts list For Phase 1 Ej20g heads on Ej22t block-

•Ej22t crankshaft position sensor
•Ej22t camshaft position sensor
•Any ej knock sensor
•Ej22t rear engine connector bracket
•Leg/wrx ej20g or coolant pipes
•Ej20g coolant crossover pipe w/ modded ej22t engine harness
•Ej22t oil pan/dipstick
•After 99' dohc timing belt tensioner bracket (bracket/tensioner)
•Inner timing covers
*Left-must match heads (leg,wrx)
Right-any (leg,wrx,ej25d)
•Timing sprockets
Any leggy, or wrx
•timing idlers
Any between ej22,ej20g, twin turbo, ej25d
•timing belt (gates or oem)
Ej20g leggy or wrx
•outer timing cover
Any
•headgaskets
Ej22t

Also between the Ej22t or Ej20g intake manifold, which would be the better option? I am thinking of doing AWIC install as well.

[mike-tracy]

So compatibility wise, is this everything I would need for a dohc swap with a 22t block and 20g heads?
Also between the Ej22t or Ej20g intake manifold, which would be the better option? I am thinking of doing AWIC install as well.

It's gotta be pretty close to everything you need. I usually hit up the junkyards to grab stuff I forgot off ej25d engines (cam cover bolts, timing covers, stuff like that). All the sensors should to be 1st gen legacy, though if you use a later knock sensor, you could repin the 1st gen connector onto the new stuff. I use the ej22t coolant crossover pipe since the ej22t intake manifold wiring harness obviously fits perfectly.

You need an 10mm oil pump (should get one off a non-spun bearing ej22t or ej25d). Timing kit for an ej25d (there are 2 variants, as long as you get the complete kit, you should be fine). Water pump depends on if you have the oil cooler or not. If you have it, then 1991 ej22t or 2002-2005 WRX one is what you want. If no oil cooler, then 1992-1994 ej22t water pump is it.

Ej22t intake only fits phase 1 sohc heads. All phase 1 dohc manifolds fit all phase 1 dohc heads. Use whatever you can get your hands on, but if you plan to use wasted spark (as opposed to converting to Coil on Plug), then an american N/A ej25d manifold is convenient for that.

You sure none if this info was in this thread already?

[LilLegacy]

Ej22t intake only fits phase 1 sohc heads. All phase 1 dohc manifolds fit all phase 1 dohc heads. Use whatever you can get your hands on, but if you plan to use wasted spark (as opposed to converting to Coil on Plug), then an american N/A ej25d manifold is convenient for that.

You sure none if this info was in this thread already?

So EJ20g intake manifold it is haha. (sorry for that noob question I still have a lot to learn )

I did a good amount of reading since my last post but i'm still unsure on some things. So I found someone selling a pair of EJ20g heads and an intake manifold from a 91 Legacy RS. These heads have a 57cc right? Combined with the EJ22t, will this create too low of a CR to run with stock internals?

And yeah you're right haha... most of that info was in the thread but I made this compact list for myslef and thought I might as well post it cause it might help make it a little easier to see everything in one spot.

[mike-tracy]

I'm not sure exactly which ej20g heads had what combustion chamber. Rob has a tune for lower compression builds, but it would be good to get ahold of him first.

[LilLegacy]

Thanks for the info mike-tracy. I have reached out to rob.

[EJ22D]

Update to thread:

DOHC heads are not limited to low compression. They can also be used to spike compression with the right head gasket thickness.

Any WRX or STi timing belt assembly can be used in Phase 1 DOHC rebuild. I am using a full EJ257 timing assembly in my EJ22D.

Ej25D heads have just as much potential as EJ20D, EJ20R, and EJ20K heads once portwork and cams/valve springs have been redone for performance.

Phase 2 coolant crosspipes (the ones used in the EJ205, EJ255, EJ257, etc) can be used in the Phase 1 DOHC rebuilds. Two out of 3 wires from from the Phase 1 harnesse match the Phase 2 connector wiring for the coolant sensor. The front left inner part of the intake manifold must be ground down a bit to fit if it is the 1996 big plenum 25D type.

DOHC heads are an extreme upgrade over any Phase 1 SOHC head and with some work will meet a Phase 2 head on even ground. The ECU that will run said heads will do so without an issue.

[adema2626]

Bump from the dead, but the ej18/ej22 n/a crossover pipe appear to be the same as the ej20g crosspipe. If anyone is still doing this swap.