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Thread: EJ25D

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    EJ25D

    so i have a ej25d out of a my outback and im looking to rebuild it and wanted to know if any one knows if i can use the heads off of a ej251. the only thing i know that is different is that its a sohc and my engine is dohc. but will the timing work.

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    System Operator IGOTASUBARU's Avatar

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    I never did that so I have no idea.
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    I don't believe so, but I could be wrong.

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    Kenny's Avatar

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    The 251 head will fir on top of a 25D block. They are a bore and port match. You will need to make sure that the timing components are correctly to the 251 heads. The only problem, the 251 top end is only compatible with the top end (intake manifold, etc..), engine wiring, and ECU of cars that originally came with a 251. So in order to run it in your car, you will need to merge the harnesses and use a 251 ECU. I do not think it is worth the time, money, and effort.

    The 251 is a SOHC, so you will need the matching timing belt. I'm pretty sure that they share the same gears and pulleys, but I'm not 100% sure. Also, make sure that you use the original 25D two-piece tensioner during your engine rebuild no matter which way you go with the top end. The single piece is garbage. If the 25D currently has the single piece, you will need to swap out the tensioner mount that bolts to the block. They are different. And make sure that you use the OEM 25D head gasket from the dealership.

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    Thats what I was thinking. It IS possible, but not worth the time, money, and effort.

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    time is not a problem, i have a jdm engine under my hood right now, see what i wanted to is just get more power, and there are na camshafts to do that, so i was thinking about doing this because what have is if i run 6pis of boost with the stock dohc it would only last for about a year before burning out the engine, but i read some where that the sohc heads can take it. i really want to go na but i can not find parts other than intake and exhaust, but if you know a site where can get better cams that be help full,

    thank you for the help,

  7. Top Of Page | #7
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    Well, first NA power is not particularly easy to make and be reliable. Second, the DOHC heads are just fine to use for boosted motors. In fact, they're great head for it! The problem though, is the lower end. The 25D and 251 lower ends are NOT made to handle very much boost with any reliability. They are an open deck design and can't handle the pressure of boost. The block is the reason you can't go turbo easily, not the heads. But, if you want to go turbo... The ECU, harness, and harness merge are pretty much required for you car. There is no way to go turbo otherwise.

    For NA power, thinner Cometic 0.027" head gaskets will increase compression some. You can also have your OE 25D cams reground. Delta cams make very good, reputable cam regrinds. They have several options. Check out there website. You can add phenolic spacers, headers, a lightweight crank pulley, and even an MSD coil pack. These will all help you increase the performance output reliably. Don't even bother with a CAI of any sort. Just throw an AEM filter into the stock intake box. That's the most efficient way to go. As far as cams, focus on something that will increase the power in the lower range. Having lots of low end power and a broad torque curve REALLY make a huge difference.

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    Take it from someone who considered doing NA builds, turbo builds, total swaps and the like. If you are unhappy with the power, get a turbocharged car. I'm happy I did. Less headaches and more reliability.

  9. Top Of Page | #9
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    OK, yeah see what you saying, thank you, i think i might just rebuild the engine now and keep all stock and look into a wxr wagon and go from there,

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