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2000 Impreza RS <Red>
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1,197 Posts
Did anyone ever think of putting Legacy SS 2.2 heads on an n/a 2.5 block?

The head chamber volume of the Legacy SS heads is only 40cc.

If you put those heads on an EJ251 block with STI head gaskets (11044AA642), you'd end up with a compression ratio of 11.4:1 AND a proper quench area to boot.

Add some cams and EM and I feel like you'd have quite a screamer.


Just some thoughts recently floating through my mind.

Carry on.... :rolleyes:
 

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RUSSIAN FOR HIRE
2000 Impreza RST
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2,425 Posts
the legacy heads actually have smaller valves than the NA 2.2 heads which makes them a worse option. wouldnt work too well unless you bore out and intall aftermarket valves.
 

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97 Acadia Green OBS
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126 Posts
In on this. Picked up 2 good EJ25D engines for cheap.

Putting early dual port Legacy heads (For exhaust options) with later roller rocker/SLA assemblies on. Probably going to run Delta 1000 cams and build a 4/2/1 header into a 2 1/2" exhaust.

Car is my daily, but the 2.2 with #4 slappin (da bass) and 230k miles is uninspired at best. In the process of prepping the shortblock and cannibalizing my dad's Subagon/Vanaru engine for the heads. He can have my singleports.
 

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2000 Impreza Outback Sport
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222 Posts
Yodanny, did you use delta cams or something else?

BTW my frankenmotor still running tops, about 8k miles now. I made a custom UEL header for the single ports, both stock cats, WRX mid-pipe and an old 5zigen axle-back. The car sounds nasty and has gotten many complements. A few people have actually thought that I did a WRX swap from the way the car pulls off the line. I picked up a K&N panel filter and ganzflow pipe, to install over the weekend.
 

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Premium Member
2005 Legacy GT, 1977 Jeep CJ7
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1,222 Posts
mkay, i got a question/idea....the ej253 has a compression ratio a bit higher correct? but swapping one into a non avcs is not plug and play. if ej251 heads were bolted onto a 253 would you get a higher compression ratio but the added benifit of better flowing heads than 2.2 heads. use the 251 intake manifold and its plug and play right? idk maybe im just dreaming of getting back into a gc chassi car with more hp but not turbo.
 

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Premium Member
overdeveloped beater
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8,335 Posts
Discussion Starter · #188 ·
I talked about the later pistons earlier. You would want to check the dome and make sure it won't hit anything when bolted together.
 

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Premium Member
2005 Legacy GT, 1977 Jeep CJ7
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1,222 Posts
Sorry storm i must have missed that. That wojld be a nic setup. Now if thete was only a way to uze the 05+ intake manifold.
 

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2000 OBS
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421 Posts
so, i am finally deciding to fix my 00 obs. the bottom end has a wicked knock.

i purchased phase 2 ej25 block from a member here a while ago, and im deciding to put it into my car.
parts so far
phase 2 2.2 heads (stock on my car)
phase 2 2.5 sohc block
phase 2 2.5 sohc cams
bottom end rebuild kit
11044AA642 sti head gasket set

i do have a question about the head gasket set i picked up 11044AA642. this is for an 04-05 sti.. does anyone know what thickness these are, and should i be looking for another set? what comp ratio may this give me?


*edit.. crap, i think i bought the thin gaskets by accident. anyone have a new thick gasket set 11044aa610? maybe want to trade?
thanks!
 

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2000 Impreza Outback Sport
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222 Posts
I would personally use the updated headgaskets for the 2.5L phase2 you are going to use. The Frankemotor thread on Nasioc should contain more related info that you are looking for.
 

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2000 2.5RS 4dr / 2005 STi
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86 Posts
Just blew my HG on my 99 GF 2.2 :(

ok Im a total noob on this one but I read the whole thread.

So my plan is to re-use my 2.2 heads and mate it with 2.5 phase 2.

Is the phase 2 2.5 came from 99-01 RS and 00-01 forester?

should I use 04-05 sti HG for this combination.

What are the gains on this setup?

Thanks in advance.
 
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