The DOHC installation 'unspoken' details thread

[Grayguy]

Ok, this hasn't really been covered in this thread yet, and I've gotten a few PM's about it. Here's a few quick pics and an explanation of how to set the NA heads up for a turbo.



It's been almost 3 years since I did this, so bear with me. I believe the Adapter for the Oil feed is a 10x1.25mm to -4 AN fitting.

For the water line, I drilled and tapped it for a 1/4" NPT fitting. I then used a (I believe) -6AN adapter.

For the Oil return, I just bought the closest size drill bit I could get to matching the oil return tube off the 22t heads. In hind site, I should have used a larger tap/fitting and used an AN line here too, I still may rework it to do just that.



Feel free to quote/ edit this if you have more details on the sizes, like I said, it's been quite a while since I did this.

[93forestpearl]

Max, the oil feed is a M12x1.25 thread. -04 AN is the common outlet for people running non-factory setups. A factory banjo bolt should work just fine too. Banjos suck ass though.


www.anplumbing.com has the adapter.

[JRMSTI]

anyone know where i can get an early legacy ej20g rear timing cover, since its looks like from this thread i cant use ones from different engines

[JRMSTI]

bump

[cj91legss]

you should be able to use some from some of the legacy gt models

[JRMSTI]

you should be able to use some from some of the legacy gt models

are you referring to usdm legacy gt from 96 or the jdm 1st gen?

[cj91legss]

from the 96 i think

[__TT__]

Just a little fyi on the left side head egr plug.

For the ej25d heads it is a M16 x 1.50 thread.

Look for it in the automotive drain plugs at Ace hardware.

[92 Rally]

Has anyone tried using ej257 heads?

[PhyrraM]

Has anyone tried using ej257 heads?

There is at least one with a USDM WRX/STI swap. However, using those heads would mean wiring up the OBDII ECU and harness as there are serious sensor and pulley differences.

This thread was intended as a accumulation of information on adapting phase I DOHC heads (and complete motors) using the factory or simpler EJ20G ECU and harness.

[92 Rally]

Would you have a link for any information pertaining to that? I would like to look into it as I have a almost complete ej257 laying around.

[PhyrraM]

No link, but the procedure will be the same as a "WRX swap writeup" on Nasioc or RS25.com. Full harness merge with the Legacy.

Here is the only Legacy I can remember doing it:

http://bbs.legacycentral.org/viewtopic.php?t=37406

[fasterthanyou]

Ok, this hasn't really been covered in this thread yet, and I've gotten a few PM's about it. Here's a few quick pics and an explanation of how to set the NA heads up for a turbo.


For the Oil return, I just bought the closest size drill bit I could get to matching the oil return tube off the 22t heads. In hind site, I should have used a larger tap/fitting and used an AN line here too, I still may rework it to do just that.

Feel free to quote/ edit this if you have more details on the sizes, like I said, it's been quite a while since I did this.

also for the oil return you could just run it down to a bung welded onto the oil pan. and you could run no coolant through the turbo. my friend is doing this right now, until he taps his head.

for those doing a 25d head swap, remember that the NA heads have a large "squish area" and it will therefore drop your compression when applying to a 22t.

[x2hawt4ux]

can some one please help me out. i have a set of 25d heads and the intake manifold.

1. what do i need to know when using these heads?
2. do i have to use a 25d manifold or can i use an ej20g?

from what ive read it is complicated to make the 25d heads work. what are the important things i need to buy/ replace when doing this conversion. The only dohc stuff i have are the complete heads and complete intake manifold.

i tried reading as much as i could but i just cant figure it all out.

thank you!

[__TT__]

Use the 25oil intake. Youll need to plug the egr port. Also there is a hole on the driver side head that needs to be plugged. Then aside from the turbo oil and coolant lines thats really about it. Reax this entire thread about 10 times before taking this on

[bmxkelowna]

i know its been said before but i just wanted to let everyone know that ej20k cams work perfectly in the ej25d heads. as well as newer (04ish) sti valve springs with there retainers, seats and valve keepers all work in the ej25d heads too

while i was doing the swap we noticed the 04 sti valve springs from the b25 heads are the identical size to the ej25d ones. meaning the exhaust valves would be a good upgrade (as far as i know the turbo valves take heat and abuse better)

[mx4life]

I have a EJ20k in my car now. was running the slanty till i got more parts. Im using the stock 22t Throttle body and my ver4 tmic wont fit. do I need to cut my long throttle body down?

[macipusy]

Fasterthanyou....if by squish area you mean the combustion chamber, then pahse 1 DOHC heads have a 46.6 cc chamber, same as the ej22t heads. CR should remain the same. I am not 100% positive if there was any difference between the 95-96 and 97-99 heads....the combustion chambers have a different shape and the valves are different sizes.

If you go to the JDM 2.0L heads, those have a 49cc combustion chamber, as do the USDM WRX heads. STI heads are close to 54cc combustion chambers.

[MikeyMeyagi]

Fasterthanyou....if by squish area you mean the combustion chamber, then pahse 1 DOHC heads have a 46.6 cc chamber, same as the ej22t heads. CR should remain the same. I am not 100% positive if there was any difference between the 95-96 and 97-99 heads....the combustion chambers have a different shape and the valves are different sizes.

If you go to the JDM 2.0L heads, those have a 49cc combustion chamber, as do the USDM WRX heads. STI heads are close to 54cc combustion chambers.

this is incorrect. the 22t heads have a 40cc combustion chamber and the 96 HLA 25d heads have 52cc if i recall, i measured these myself. the 97-99 25d heads with the clover shaped combustion chamber have 46.6cc Using the 97-99 heads is your best bet on stock pistons, your CR will be about 7.6:1, which on paper sounds low however i have had this motor setup for 3 years now and i can assure you off boost driving has plenty of power, and with a vf23 at 18psi i was making 260-280 ish awhp. the problem with using 257 heads or 96 HLA heads is i dont believe there is enough material on the head to seal the headgasket due to the difference in bore size. Which sucks, because the ports on the HLA heads are alot bigger then the 97-99 heads....

[MikeyMeyagi]

i know its been said before but i just wanted to let everyone know that ej20k cams work perfectly in the ej25d heads. as well as newer (04ish) sti valve springs with there retainers, seats and valve keepers all work in the ej25d heads too

while i was doing the swap we noticed the 04 sti valve springs from the b25 heads are the identical size to the ej25d ones. meaning the exhaust valves would be a good upgrade (as far as i know the turbo valves take heat and abuse better)

the 257 valves will not work in the 25d heads due to length differences.

[macipusy]

According to Weisco Pistons Subaru chart, they list the ej22t heads as 46.6cc as well as the ej25 heads for their off the shelf drop in pistons. All their specs look correct otherwise for other models listed, so I am unsure why they would provide incorrect information for the ej22t.

I have measured the clover type ej25 heads at 46.6cc but never personally measured the 22t heads. I guess this needs to be done for verification.

There had been people who documented measuring volume on ej22e heads at 41cc. Next question would be if the combustion chambers between the 22e and 22t heads are the same.

[PhyrraM]

Weisco's (and other piston manufactures) charts have errors. I know that they have errors in rod lengths for sure, so I would not take it at face value and double check everything for accuracy

[MikeyMeyagi]

22t and 22e have the same size combustion chamber AFAIK

[macipusy]

I did some more digging around, and in seems the ej22e and ej22t have the same combustion chamber volumes....about 41cc. Seems the only difference in those heads are the larger exhaust valves on ej22e.
I will do a measurement to verify for 100% once I find a set I can borrow.

Sucks that companies like Weisco publish spec material full of garbage data. I would of been screwed if I bought off the shelf weiscos and did my CR calcs off their specs...I was really close to doing this, but decided to design my own specs for custom CP Pistons instead

[DevC]

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.