Frankinstein engine

[iluvdrt]

Will EJ25 DOHC N/A heads fit on a WRX EJ20 block? Just curious, I am trying to do a cheap (respectively)turbo conversion while maintaining my stock harness. I plan to run a piggy back s-afc to help tune it.

 

My ride, 98 Legacy GT wagon

 

Thanks,

 

-Jason

[Numbchux]

yes, you'll probably need to match the intake manifold to the heads....

 

and IIRC the coolant lines for the turbo come out of the head...but don't quote me on that

[Hodaka Rider]

http://forums.nasioc.com/forums/showthread.php?t=505723&highlight=ej22T

 

There ya go. It's mostly talking about the EJ22(turbo), but it has info on the newer EJ20, as well. Lots of reading to find actual answers.

 

Here's more head/block info: http://wac.addr.com/auto/obs/turbo/ejcalcs.html

[iluvdrt]

yes, you'll probably need to match the intake manifold to the heads....

 

and IIRC the coolant lines for the turbo come out of the head...but don't quote me on that

 

I plan on using the heater hoses...something about dumping super heated turbo coolant into a head bothers me.....plus my heater will be super hot.

 

 

Thanks for the info.

[86BRATMAN]

if i'm not mistaken, and i very well could be its been a while since i did my research on the lg gt's, but you have a phase one ej25, and these heads on a wrx would lower the compression ratio, anyways here is a good point of reffernce as to head/block combo's and the comp ratio they would yield

http://wac.addr.com/auto/obs/turbo/ejcalcs.html

[iluvdrt]

if i'm not mistaken, and i very well could be its been a while since i did my research on the lg gt's, but you have a phase one ej25, and these heads on a wrx would lower the compression ratio, anyways here is a good point of reffernce as to head/block combo's and the comp ratio they would yield

http://wac.addr.com/auto/obs/turbo/ejcalcs.html

 

You are right, but it will be boosted and professionally tuned, so C/R's are really not my to big of a concern..especially lower ones.

 

Thanks for all of the insightful info everone.

[86BRATMAN]

always a good idea for a good tune, if you are planning on doing some higher boost figures i'd recommend a cometic metal head gasket set, just some extra insurance, www.cometic.com i think is the site, i've seen these gaskets hold over 40 psi on some built hondas

[86BRATMAN]

another thing to look at is that most wrx motors, the jdm versions anyway were already dohc, and they can be had usually cheaper than the usdm counterparts, and those heads will flow much better than the phase1 25's do

[iluvdrt]

I am going to keep my heads because I know my mainifold, and cam sensors, and such will bolt up. I am trying to avoid as much re-wireing as possible.

 

As far as my heads go they are getting a P+P, new springs, 3 angle valve job and seals. I think they will be fine until I need more power. I am only shooting for 300 crank HP, which will be low boost, and easily attainable.

Basically I want to keep up with my buddies EVO (stock) and have a little more umph on the highway. I am not trying to build a 450 awhp beast.

[86BRATMAN]

when i put a 91 ej22 into a 95 legacy about two years ago, i had to change out the most of the motors sensors due to the different plugs on different obd models, there was nothing to it really, unscrew and re screw or bolt where they go, no re-wire needed, and you are going, most likely, have to do this anyway between the two motors, i would keep the ej20 heads and intake manifold on the ej20 just for the sake of knowing that the tmic will fit between the manifold and firewall without having to mod anything, the a/c lines get in the way otherwise, take a look at the im's the wrx is shaped different to utilize the tmic, and if you were to upgrade to an sti tmic it will not fit with the ej25 i/m,

and i'd just about put money on the wrx heads flowing better than the ported phase one ej25 heads even in stock form,

[iluvdrt]

when i put a 91 ej22 into a 95 legacy about two years ago, i had to change out the most of the motors sensors due to the different plugs on different obd models, there was nothing to it really, unscrew and re screw or bolt where they go, no re-wire needed, and you are going, most likely, have to do this anyway between the two motors, i would keep the ej20 heads and intake manifold on the ej20 just for the sake of knowing that the tmic will fit between the manifold and firewall without having to mod anything, the a/c lines get in the way otherwise, take a look at the im's the wrx is shaped different to utilize the tmic, and if you were to upgrade to an sti tmic it will not fit with the ej25 i/m,

and i'd just about put money on the wrx heads flowing better than the ported phase one ej25 heads even in stock form,

 

I was planning a FMIC, not a TMIC in order to make the best from the EJ25 mainifold. I am not planning this to only take a week, I am sure Ill have to make a few adjustment here and there.

If I were to use a EJ20 block heads, and I/M than I might as well call this a WRX swap and change everything over, have the harness merged and use a WRX PCM. That would defeat the purpose of my "cheap" build.

 

I have $500 in this now and all I need is a EJ20 block,cross member and S-AFC. Everything else I already have.

[86BRATMAN]

I was planning a FMIC, not a TMIC in order to make the best from the EJ25 mainifold. I am not planning this to only take a week, I am sure Ill have to make a few adjustment here and there.

If I were to use a EJ20 block heads, and I/M than I might as well call this a WRX swap and change everything over, have the harness merged and use a WRX PCM. That would defeat the purpose of my "cheap" build.

 

I have $500 in this now and all I need is a EJ20 block,cross member and S-AFC. Everything else I already have.

 

ok, that sounds like it'll be a good functioning setup in that arangment, have you considered port matching the manifold to the heads once they are done

[iluvdrt]

ok, that sounds like it'll be a good functioning setup in that arangment, have you considered port matching the manifold to the heads once they are done

 

no, I havent. It may be something to consider. I am just trying to get a little more umph.

[86BRATMAN]

no, I havent. It may be something to consider. I am just trying to get a little more umph.

 

since everything will be apart anyways it woould be worth it to have the im match ported and afterward check the gaskets and trim if needed just so you won't have nice big ports and matched im being restricted by a smalled gasket, this in no way comprimizes the gasket if it is done correctly and time and care is taken

[970subaru]

and i'd just about put money on the wrx heads flowing better than the ported phase one ej25 heads even in stock form,

wrong. not only are DOHC ej25 heads the same castings as ej20k/h JDM heads, they are far better than usdm wrx. they really are some of the best flowing heads subaru has made, and at 260 cfm intake outflow stock LS1 and several aftermarket aluminum V8 heads as well at a pitiful .345" valve lift intake. ported and with a more decent lift, I'd imagine mid 300's cfms would be possible.

people have made close to 500whp with non ported ej25 heads and some special cams. porting is pointless for a turbo build however.

[86BRATMAN]

wrong. not only are DOHC ej25 heads the same castings as ej20k/h JDM heads, they are far better than usdm wrx. they really are some of the best flowing heads subaru has made, and at 260 cfm intake outflow stock LS1 and several aftermarket aluminum V8 heads as well at a pitiful .345" valve lift intake. ported and with a more decent lift, I'd imagine mid 300's cfms would be possible.

people have made close to 500whp with non ported ej25 heads and some special cams. porting is pointless for a turbo build however.

 

interesting, i didn't know that, i have always been told they are junk, that the phase two's flow better

[970subaru]

interesting, i didn't know that, i have always been told they are junk, that the phase two's flow better

PII(SOHC) are great as well. they also can rev to the moon in stock form due to the really light valvetrain with roller rockers(single cam is a lot less mass in parts to spin than DOHC)