Head Swap

Its been a while since I looked at this, but if I remember right, the 22 heads have a smaller chamber volume than the 25 heads, so the "torque" your buddy is talking about really is higher compression ratio. If I remember right though, the 22 heads don't flow as well as the 25 heads. Someone on here will have numbers I'm sure...

Its been a while since I looked at this, but if I remember right, the 22 heads have a smaller chamber volume than the 25 heads, so the "torque" your buddy is talking about really is higher compression ratio. If I remember right though, the 22 heads don't flow as well as the 25 heads. Someone on here will have numbers I'm sure...

Dont got numbers but that is exactly right. The don't flow as well, but create more compression, not worth the hassle in my opinion. If you don't have a GT 2.5, then just get a GT head (DOHC) and slap it on there and you will be good to go. Lol.

I have a 97 Legacy GT

Well then that is stupid to change the heads to the 2.2. DOHC is much better, and with what you have right now, is the best output for the 2.5 you can get without adding or rebuilding it.

We usually upgrade the SOHC 2.2 to the 2.5 DOHC on the ej22t's. It's a common upgrade. You wouldn't want to go backwards.

Would it be possible to do a head swap on an EJ22 to EJ25 headers? would that be Benificial?, or would that just be another moot tradeoff?

I thought that it sounded kind of weird...but I didn't know enough about subie performance to argue it.

It's all good. You gotta start somewhere. I learn new stuff on here EVERY DAY. Lol.

Would it be possible to do a head swap on an EJ22 to EJ25 headers? would that be Benificial?, or would that just be another moot tradeoff?

 

Are you talking about just the headers themselves? Or do the head job. Cause you said "head swap" and also "headers". Lol. I'm not sure the difference on the headers themselves between the 2.2 and the 2.5, but if you have a 2.2, the best head swap you can do is the 2.5 GT head, which is DOHC. Hopefully that answered your question?

gonna be completely forth coming here... i don't know the difference. care to educate the feeble minded? but it seems that i would want to do the 2.5gt head swap. would i have to add another cam? as my current engine is SOHC iirc.

Thanks for the help!

gonna be completely forth coming here... i don't know the difference. care to educate the feeble minded? but it seems that i would want to do the 2.5gt head swap. would i have to add another cam? as my current engine is SOHC iirc.

Thanks for the help!

 

Well I'm assuming you have the 2.2? Anyways. The camshafts are located within the head assembly (the heads that bolt ontop of the sides in which the pistons lay horizontaly), and the 2.2 has SOHC, meaning that on head head (there are two heads, one on each side of the engine) there is a single cam that is timed with the timing belt to operate the lifters and to preform your intake and exhaust strokes. Basically, DOHC (dual) gives each head TWO camshafts, which basically means more intake (as there are now TWICE as many being opened compared to the SOHC) being preformed, as well as more exhaust, which creates more power. So ultamately, to put it in very simple terms, you take of your heads with the SINGLE cam in there, and put on different heads from the 2.5 GT, which has TWO cams on each head, so now the car will have FOUR cams in total, and will make the engine emitt more horsepower and torque, at the expense of fuel economy. Any others questions just PM ME.

Aren't we forgetting one thing in advising here, that is that the 2.2L SOHC head has a single exhaust port (my 99 Legacy L) and the 2.5 DOHC head has a pair of siamese exhaust ports (my old 01 Forester L)? Not sure about earlier 2.5L heads, but just the simple fact that you'd also have to swap the headers if you wanted to swap 'down' to the higher compression, you'd wind up choking off your exhaust as well? ...... {I know I did hear of swapping the EJ18 heads onto earlier EJ22's though.... not sure as I never researched it.} ( I believe the 'other' Subaru board has recipes listed there.) I researched this a few years ago when I contemplated swapping in an '01 or '00 EJ22 to replace the leaky EJ25 in my '01 Forester and considered a hybrid EJ235 as a replacement if I had to rebuild one versus a salvage swap. It was a good 2 years back though. Not an expert, as I haven't tried it personally, just my $.02

Well yah.. I would expect people to figure that out when they end up having one open exhaust port where their headers should be. Lol.

Sorry to open a old post. Wanted to know if all 2.5 DOHC Heads are the same. I have a set that are 2.5 DOHC that I'm not sure what they came off of and wanted to know if I can have them rebuilt and put them on my 05 LGT

Early EJ25D DOHC heads are not the same as newer 2.5 heads. Early heads can easily be identified by EGR passages on the left head at the back.

No they are not the same. The best way to tell the difference is the casting number on the bottom by the exhaust ports. Should say D25, B25, NA LH, NA RH, S20 etc

d25 ftw

For the people with 2.2's the EJ25/22 build is a lot of fun. Doesn't flow much past 5k still. However the dynos I have seen the engine makes full torque by 1.8-2.5k rpms. Buddy of mine has a 2.5/2.2 in a brat. That thing will eat ANY 2.5 any day of the week.

 

The Frakenmotor will out pull a 2.5 in the low and mid range. The 2.5 has a better top end. However the frakenmotor is more fun because of the power it produces and when. With cams it gets even better. 95% of you have never been in one.

 

But I will tell you a 2.5 will not hang.

 

We forgetting here that numbers are not everything? I figure it makes 180-200CHP depending on altitude levels and what not.

 

But if you have a good running 2.5 there is no need to do the head swap.

The extras I have that I checked is a RH NA. I would guess this would not work then for my 2005 LGT. Are these worth anything?

I built a 2.2/2.5 Frankenmotor for my Impreza 3 months ago. It is a lot of fun to drive. The torque does come on early and holds. I have many upgrades to make on it before the summer, so I have been driving the Legacy most of the time.

Having to pull the motor to swap the heads would make any tiny gain not worth it for me...

The frankenmotor is not a replacement for a good running 2.5L as the 2.2L heads do not flow near as much. Not worth the trouble. For people running 2.2L's, it is a considerable upgrade and well worth it if parts are sourced at decent prices.

 

It does depend on your resources, experience and research. I read about it for a month before I started. Pulled the motor on a Saturday, ported the 2.2L heads, intake, lots of cleaning/paint and it was back together with the 2.5L bottom end on Sunday afternoon. Well worth the time for a power gain you can feel.

If you are swapping 2.5 heads on a 2.2, what kind of EM do you have to do? Piggyback?

If you are swapping 2.5 heads on a 2.2, what kind of EM do you have to do? Piggyback?

 

Putting 2.5 heads on a 2.2 will lower compression and power output...

 

Running 2.2 heads on a 2.5 block requires no electronic modification, it will run on the 2.2 harness and ECU. Gains may be had by a piggyback.