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Old 04-17-2008, 10:39 PM   #1
Splinter
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Default EJ25D -> V4 STI head conversion

While technically not bolt-on, I felt that this was relevant to this topic.

I lost oil pressure and wrecked the oil journals in my V4 STI heads, and since the castings are the same, I decided to use EJ25D heads to replace them.

The only real modification I made was to the passenger side head, which needed oil and coolant lines to be drilled and tapped for the turbo. People seem to like messing around getting oil and coolant from other parts of the engine, but I dont see why since the bosses are right there, and the factory banjo lines work perfectly.

Here is the back of the head as it comes from the factory.


Drilled out the oil return at the bottom of the head to 15mm, and the coolant boss to 7/16", then tapped it with a 12x1.25 bottoming tap. The oil boss is already drilled and tapped from the factory, it just has a plug in it.


With the banjos installed
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Old 04-18-2008, 03:38 PM   #2
mxpunk
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nice, i plan on doing the same if i ever get a set of these heads
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Old 04-21-2008, 01:03 PM   #3
Jaxx
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is the chamber volume the same?
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Old 04-21-2008, 03:13 PM   #4
Splinter
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I didnt measure the chamber volume, but the castings were identical as far as I could tell with the naked eye.
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Old 06-21-2009, 09:35 PM   #5
IllNastyImpreza
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GT30R, closed deck madnes

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Can you elaborate which is your feed and return ? I need oil feed & return for my GT30R when I install it in the near future. Would this be the best place to go for the oil ? What parts would I need to do this ? IE, what banjo bolts and whatnot ?

would it not be better/easier to go this route for feed?


Last edited by IllNastyImpreza; 06-21-2009 at 09:40 PM.
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