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04 Forester X, MT
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1,039 Posts
Discussion Starter #1
Here's a thought ... Did they ever make any 2.5 Turbos that were SOHC with semi-closed deck head design? I would like to try and obtain some so if-when I have a head job I can get some better heads so the head gasket repair will last.

I know for '04 Turbos are DOHC and for '05+ all are DOHC.

Call me weird, I just like SOHC better for the simplicity and ability to adjust valves without playing the "shim game". :biggrin:

Looking at some parts lookup choices, it seems there were no SOHC 2.5 Turbos made, so if you want the semi-closed head deck design you have to go with DOHC heads.
Are the cams the same on Turbos as non-turbos?
In 2005 they also went to the variable valve timing design, so that is another complicating factor?!
 

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2003 XS
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169 Posts
The engine block is the issue, not the heads, per se. You'd need to do a complete engine swap from NA to Turbo to fix the issue. If you are going to do that, you are better off just buying an XT.
 

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04 Forester X, MT
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1,039 Posts
Discussion Starter #3
oh, i must have misunderstood pics.

the point is i don't want a turbo but i do want a reliable engine. i think this may be my last subaru unless they make some changes.
 

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Premium Member
2008 Forester X Premium 5MT
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8,071 Posts
The heads are all closed deck. What changes is the block.

No there were no SOHC turbos.

Putting a turbo on a EJ25 SOHC can be done but the cost vs benefit is not in your favor. Especially if you want a closed deck, you are looking at a ground up build with a EJ257 block modified by outfrontmotorsports. Since the block is being machined and internals have to be installed it would be stupid to do a build around NA internals. A cost effective crank would be a STI crankshaft. Rods would have to be WRX, STI or aftermarket. Same with pistons, WRX, STI or aftermarket. Basically a built EJ257 short block offered by outfront, $3,500.

The heads in the end would be a limiting factor, they don't flow as much as the DOHC out there. This would be a bottle neck.

Engine management based on SOHC heads and wiring harness would have to be done by a stand alone like a Hydra which will set you back about $1,700.

So you are at $5,200 and you still need all the supporting items like the turbo, turbo piping, intake, timing belt, water pump, oil pump, idlers, gaskets, machine work.............and the list goes on. May as well tack on another $3,000+. Then there is tuning.

So in the end the quest for a simple EJ25 SOHC engine engine with a turbo and a closed deck block is not so simple. What you try to make simpler by eliminating 5(?) parts(2 camshaft pulleys, 2 camshafts, 1 camshaft position sensor...) is pointless, The SOHC actually has more parts with all the rocker arms and rocker arm shafts vs a shimless bucket DOHC.

For a cost effective closed deck turbo look at EJ20/22 turbo engine swaps. Find a donor car, or pick every thing(engine, ECU, wiring, turbo/piping......) up via a JDM importer like gruppe-s or let a place like ECS Performance handle every thing.

Or just settle for a semi-closed deck EJ255/7 that don't have nearly the issues of the open-deck EJ25 NA. At that point just trade yours in for a XT.
 

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Premium Member
2008 Forester X Premium 5MT
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8,071 Posts
oh, i must have misunderstood pics.

the point is i don't want a turbo but i do want a reliable engine. i think this may be my last subaru unless they make some changes.
One can also do a build around a EJ255/7 (semi-closed deck block) with NA internals and SOHC heads. Source a EJ255/7 block and rebuild it with NA rods and NA pistons. All the other supporting items will fit with out issue. Not many people would even know it was a EJ255/7 block while looking at it.
 
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