12 replies to this topic

[meatball]

I have seen 2.5rs owners drop a legacy 2.2 bottom end with the 2.5 heads. Does the bottom end of the 2.2 drop right in without custom motor mounts?:wave:

[DerFahrer]

The EJ25 is basically an EJ22 bored and stroked... Although I've never heard of what you speak of, it wouldn't surprise me... Almost any Subaru motor can be swapped into almost any other Subaru without extensive modifications...

[Dr. RX]

Actually the 2.5 is not simply a bore and stroked 2.2. If memory serves me correctly, one is a closed deck short block and the other is an open deck short block, and therefore the heads would be different. I believe this change came about in 1997, and all the EJ22Ts were build before that. I have an EJ22T and an EJ20G (Turbo engine) that I'm going to try to see if there head swap will work on, both are about the same age, one is a 93 the other is a 92. I have no need for the engine at the moment, so it is not something I'm going to be building soon.

[DerFahrer]

Okay I'm half-wrong. I forgot to read the "turbo" part for some reason... :brolleye: Yes an EJ22T is a closed-deck block, and the EJ25 is open-deck...

However, that does not mean you cannot interchange their heads. In fact a guy has made a complete monster out of a stock EJ22T block by bolting DOHC EJ25 heads to it. That lowered his CR to about 7.5:1, allowing him to up the boost to about 22-25 lbs, and then the DOHC setup allowed him to reach 8000 rpm... And on the Legacy forums, a guy is sorting out the EJ20-heads-on-EJ22T issue as we speak...

[electryc_monk]

makes me wanna ask (so I am) which forum is this? I haven't been to any in well a coon's age for that fact alone.

[Legacy777]

if you put 2.5 heads on a 2.2 you will reduce compression ratio and engine will suck.

However the reverse is true also. 2.2 heads on a 2.5 will give a very high comp ratio n/a motor, so much that you'll need to run premium.

[CROSSTBOLT]

Please define "open" and "closed" deck. Remember, put it in terms a four year old can understand!

[alias20035]

Originally posted by CROSSTBOLT
Please define "open" and "closed" deck. Remember, put it in terms a four year old can understand!

Closed deck blocks are closed where the heads are attached, with small coolant passages around the cylinder bore.

Open deck blocks are totally open with enormous coolant passages where the heads are attached.

Closed deck blocks are more expensive to manufacture because they must be sand cast.

Basically a foam model of the desired part is made, and then the openings are filled with sand. Molten aluminum is poured into the mold which melts and replaces the foam. After cooling the sand is blown out. Extensive machining is then required to bring the block within tolerences.

Open deck blocks are "open" and thus can be die cast. Die casting involves injecting molten metal into a splitable mould. When the metal cools, the mould is split and the part is removed. Only minor finish work is required on the cast part.

Closed deck block engines are stronger than open deck blocks.

See this link for more information and photoshttp://www.legacycen...ibrary/deck.htm

[legacy92ej22t]

Originally posted by Dr. RX
Actually the 2.5 is not simply a bore and stroked 2.2. If memory serves me correctly, one is a closed deck short block and the other is an open deck short block, and therefore the heads would be different. I believe this change came about in 1997, and all the EJ22Ts were build before that. I have an EJ22T and an EJ20G (Turbo engine) that I'm going to try to see if there head swap will work on, both are about the same age, one is a 93 the other is a 92. I have no need for the engine at the moment, so it is not something I'm going to be building soon.

The EJ22T is closed deck and the EJ20G is closed deck, however the EJ22 n/a is open deck and went into production in 1989 IIRC. I think what subyluvr was saying is that the EJ25 is basically a bored and stroked EJ22 which is true. Subaru stopped making a closed deck 2.2 in 94. IIRC the EJ20G lasted a bit longer in the V1 and V2 sti. That may be the engine you're thinking was stopped in 1997? Aren't the new gen Subaru turbo engines, EJ20T and the sti 2.5T (can't remember the engine code), semi closed deck?

[Legacy777]

2.5T is the only semi-closed deck block.

[meatball]

So what is the best hybrid motor setup? The 2.5 rs heads on the impreza are a SOHC, but if i am not mistaken the heads on the 2.5 Legacy are DOHC. So when creating a hybrid turbo motor which bottom end and heads will be more benefitial for higher boost?

joe

[legacy92ej22t]

Originally posted by Legacy777
2.5T is the only semi-closed deck block.

Ahhh, ok

[Legacy777]

Originally posted by meatball
So what is the best hybrid motor setup? The 2.5 rs heads on the impreza are a SOHC, but if i am not mistaken the heads on the 2.5 Legacy are DOHC. So when creating a hybrid turbo motor which bottom end and heads will be more benefitial for higher boost?

joe

All depends on how you're building the motor. The only real difference a DOHC setup will give you is the "possibility" of a higher revving engine. But assuming you set everything else up correctly, you probably aren't going to see much gains from an extra 1000 rpm.