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Discussion Starter · #1 · (Edited)
Hi all,

Yes, I've searched and looks like this topic's been done to death... but ironically I still can't quite find the answers I'm looking for. Although I dug up some info (below), I'd to to put together an accurate & complete parts list for my upcoming engine build.
I'd like to know what engine do I order certain parts for, so I'd like to ask the community to help completing the following:

EJ255/7 block w/ EJ251 headsEJ255/7EJ251
Head gasketsx
Head bolts/studs??
Water pumpx
Oil pumpx

This is all I can think of at the moment, and of course, correct me if I'm wrong...
 

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I don't know all the answers either.

Here's how I would approach the problem:

make a composite picture of the head gaskets, and compare them to the coolant ports on your heads and block.
Here's one I did years ago to compare between factory ej22e and a felpro ej22t head gasket:
87395

Quite a bit different, eh? I downloaded both pics online from felpro and made the animation on EZGIF.COM
If you aren't 100% sure about the coolant passeges based on the pics, I'd recommend buying an ej25 turbo hg and an ej251 hg and physically laying them against the block and head.

Look up the headbolts for your heads on parts.subaru.com. I had thought the SOHC and DOHC headbolts are all the same, but it turns out subaru specifies different bolts for the inner 2, versus the outer 4 head bolts (specifically for SOHC ej25's made between 1999-2012). If you already have bolts that came off your ej251, I would reuse them unless you're shooting for 450whp or more.

Water pump: Pretty sure they all flow the same, or close enough. The difference is the main outlet and ports.
-The STI one is designed to work with a turbo radiator, and an oil cooler.
-If you plan to use a turbo radiator, but no oil cooler, you are in luck. The 1992-1994 Legacy Sports Sedan (SS) or Touring Wagon (TW) has the correct water pump and can still be ordered brand new.
-If you plan to use an oil cooler with non-turbo radiator you may be in luck, there is a thermostat housing that has a nipple that goes to the cooler: 11054AA010. These came on late 90s/early 2000s cars with the factory tow package. Out of production, out of stock but still findable.
-If you believe in the KISS method, non-turbo radiator with non-turbo water pump, just get quality parts and an oem thermostat. This setup is sufficient for over 300whp in a friend's car in Houston, Tx, with working AC.

Oil pump: I'm from the camp that bigger is not better. I've read about high flow pumps make cavitation instead of pumping oil where it needs to go, and thus I've always ran 10mm pumps on all my turbo cars. That's what came on the Single AVCS STI and ej255's (and ej22t's, and ej20h's, ej20g's etc).
 

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Discussion Starter · #3 ·
Thanks Mike!
I'm following this thread so I can keep you info handy! I'll follow up with what I ended up using in my case.
 

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use the head gaskets for the block. you'll need a single port water pump with a forward facing thermostat and its housing. use ARP head studs, you'll need an NA kit to work with the NA heads. if you plan to run the coolant tank on the upper side of the intake manifold (that the SOHC intake manfold doesn't have provisions for), you'll need a two port water pump. in addition to that if you also decide to run the OE oil cooler, you'll need a three port water pump. while looking at the front of the pump, the port off the left side goes to the oil cooler, and the ports on the right go to the heater core and the turbo coolant tank. I believe there does exist a water pump with a single port and forward thermostat, but it could be a unicorn. I've had decent luck just putting plugs on the extra two ports of my water pump. Use a turbo oil pump, but you could get away with an NA oil pump. turbo cars dont have larger pumps for the turbo, they have larger pumps for the AVCS. a 10mm WRX pump will be plenty, an STi 11mm pump would be over kill. DO NOT USE THE 12MM JDM PUMP. the 12mm JDM pump is used on a very high revving two liter dual AVCS engine. I installed one recently at a customers request on a woolman block, along with an oil pressure gauge, and big toe on the throttle had the oil pump holding 90-100psi. It's just not necessary and will give you more problems.

Other things I had to do, I also DO NOT RECOMMEND TO GO THIS ROUTE. I wish I had not done this to my car. Swap it, or dont. Do it right or do it twice, three....eight times, I got over 20k in debt building my car the wrong way just because I wanted to be different, like every one else.

I needed 8mm phenolic spacers to bring the intake manifold high enough to run a turbo inlet underneath. the inlet had to be custom made as there is no off the shelf solution. you will need to shave one of the right heads intake manifold gasket aligning dowel stand offs to make room for the turbo coolant crossover which you'll need to use due to the 257 block having a block breather that the 251 does not have. At this point, I recommend using the street version AOS from IAG, if you do this without the turbo coolant tank, you will have to get creative with the coolant hose routing.
 

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Discussion Starter · #5 ·
you will need to shave one of the right heads intake manifold gasket aligning dowel stand offs to make room for the turbo coolant crossover which you'll need to use due to the 257 block having a block breather that the 251 does not have. At this point, I recommend using the street version AOS from IAG, if you do this without the turbo coolant tank, you will have to get creative with the coolant hose routing.
Hi Silverton,

Thanks for the info and words of wisdom. One quesiton, are you aware of photos or links that show what needs to be done to the block you mentioned earlier?
 
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