ej257 motor rebuild
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This is a discussion on ej257 motor rebuild within the Engine Modifications forums, part of the Tech & Modifying & General Repairs category; I'm rebuilding an ej257 a friend gave me that rolled a bearing. The crankshaft was ground and I got all ...

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    Registered User interhead77's Avatar
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    ej257 motor rebuild

    I'm rebuilding an ej257 a friend gave me that rolled a bearing. The crankshaft was ground and I got all the proper gaskets and bearings for the motor to be put together. I have a few questions. What's the torque specs on the connecting rod bolts? The pins that hold the piston to the rod are very tight and movement is super restricted, shouldn't they move fluidly? Also is there a specific position for each piston or can you just throw it in whatever sleeve? I was also told to use high heat thread lock on the block center to hold it together...

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    Subaru Newb MainFrame's Avatar
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    I believe the torque specs for rod bolts usually come in the packaging from ARP (I certainly hope you aren't planning on using OEM bolts).


    I dunno what's going on with your wrist pins, but that doesn't sound right.


    If the block has been properly blueprinted, then yes, each piston has it's home. Each cylinder should have been bored to the specific piston going in it, and the pistons should all be numbered.. unless you're using drop-ins, but you can never get the right PTW clearance doing it that way.


    Different builders have their own ideas about what is best to seal the case halves. I would find someone with lots of Subaru specific experience and follow their recommendation.

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    Registered User interhead77's Avatar
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    What's wrong with oem bolts? Also what should I do about those pins? If I put the block together it's not like the pistons don't move smoothly. As for the proper piston postitioning, is it really bad if you do switch them? I mean there isn't anything that has to be in a specific spot for a specific reason?

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    Subaru Newb MainFrame's Avatar
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    The OEM bolts are over priced for what they are. You can get ARPs for less and they are MUCH more durable. I don't know about the pins, I'm not an engine builder, but it sounds like the rods may need more machining. It's bad if your PTW clearance is too far off.. the engine will be noisy, consume oil, and oval out the cylinders and pistons over time. They go in a specific spot because you bored the specific cylinder to fit that piston to achieve the correct clearance.

    Don't forget Subarus need a fairly aggressive hone for the piston rings to seat properly. And this isn't like assembling a Honda motor, if you put a ring on upside down or gap it wrong it's going to consume oil like mad.

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    Registered User interhead77's Avatar
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    Alright so what if I just forge it? Looking at either Manley pistons or cp and eagle H beam rods. What do you think?

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    Subaru Newb MainFrame's Avatar
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    Either Manley or CP would work. Personally I would go for something like 99.75mm so that your cylinder walls can be properly bored (depending on how worn they are). OEM pistons are the weakest point in the ej257, so it's hard to not recommend them when doing a rebuild. An engine built with forged pistons generally will not last as long as OEM though because of the greater expansion rate and looser tolerances (but it will be able to handle more power and abuse).


    The OEM STi rods are pretty stout, but in my experience they are not even close to being in balance, so I would at least have them balanced if you're going to the trouble of a proper rebuild. H-Beams aren't that much stronger, BUT they are lighter than stock rods, should basically be balanced out of the box, and normally come with ARP bolts already included. Eagle rods usually need more machine work to get the clearences right, so I usually recommend Mankey H-Beams instead. After the money you have to spend at a machine shop getting the Eagle rods within spec the Manley's end up being cheaper. (Shameless plug, I have a set of lightly used Manley H-Beam rods with included ARP bolts for sale, $240 shipped).



    Just to clear some things up, you CANNOT reuse OEM rod bolts. The threads stretch when they are installed, so they're a one time use part. Similar with OEM head studs, you may get away with reusing them once, but if you're going to the trouble of a rebuild you're better off just getting some ARP head studs.

    Since it spun a bearing there are other parts considered mandatory to be replaced. Most notably the oil cooler and the oil pump.



    There are a lot of routes to go when rebuilding an engine, but I would need to know the final goals you're wanting with it, and what the approximate budget is. As a general rule, you can figure up how much it should cost to complete the build, multiply that number by two, and that's pretty close to what the final cost will end up being.
    Last edited by MainFrame; 09-28-2013 at 02:24 PM.

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    Registered User interhead77's Avatar
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    brand new rods? ill buy them off you if they are all set to throw in with some pistons....

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    Subaru Newb MainFrame's Avatar
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    Quote Originally Posted by interhead77 View Post
    brand new rods? ill buy them off you if they are all set to throw in with some pistons....


    "lightly used" --I had them in my engine for about 2600 miles, running a base map on a vf22 (1bar spring pressure). My engine was consuming oil and I decided to go bigger with the rebuild, so the H-Beams had to go. They're in great shape since I never got it tuned for power, they never had any real stress put on them.

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    Registered User interhead77's Avatar
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    So I can just drop them straight in and that's it?

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    Registered User interhead77's Avatar
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    Ill definitely but them off of you if that's the case. Even if minor machining is needed

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    Subaru Newb MainFrame's Avatar
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    Quote Originally Posted by interhead77 View Post
    So I can just drop them straight in and that's it?

    They should drop right in.. granted you have the right fitting bearings and everything. They shouldn't need any machining, but every rebuild has some different fitments.. if you end up having to use over size bearings or something I guess there's an off chance they would need some minor work, but I doubt it.

    If you're interested in buying them PM me details and I can text you pics and paypal info.



    A nice advantage to running h-beams and forged pistons is that your rotating assembly will be considerably lighter and much better balanced. You might think about balancing your crank and flywheel, but the rods and pistons should already be within spec.

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