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Old 10-23-2012, 03:58 AM   #1
Evans2point5RS
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Default 05 sti heads vs 05 rs block

Will the heads from an 05 sti ej207 (i believe) fit on the block of an 05 rs ej253 sohc? I'm not too sure as to whether or not they will fit, or work too well, or is this not even possible?
Thanks
Ps I'm fairly car savvy but this I'm not sure about
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Old 10-23-2012, 12:22 PM   #2
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The '05 STI has an EJ257 (2.5L, not a 2.0L), assuming these heads are coming from a USDM engine.

The heads will bolt on, but without knowing what exactly you're trying to accomplish it's hard to say that it would be worthwhile.
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Old 11-12-2012, 11:47 PM   #3
Evans2point5RS
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^^^ I'm just replacing heads and going for more power. I can just get a good deal on the heads. So my question I have is: will they just bolt straight on and work or will I need to do other modification?
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Old 11-12-2012, 11:58 PM   #4
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That will not gain you any power my friend.
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Old 11-13-2012, 12:03 AM   #5
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Turbo engines have very different requirements for heads than NA engines do.
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Old 11-13-2012, 12:38 AM   #6
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They will give you less power, as they have a larger combustion chamber = lower compression ratio.
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Old 11-13-2012, 02:33 AM   #7
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^^ okay thank you.

If I change pistons to bigger pistons or to match the ej257 heads would that help or?

Thanks for the input
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Old 11-13-2012, 06:45 AM   #8
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Quote:
Originally Posted by cal_look_zero View Post
They will give you less power, as they have a larger combustion chamber = lower compression ratio.
Actually no. The dome isn't larger at all. In fact it has a better shaped combustion chamber that better propagates the flame. The difference in compression ratios come from the pistons.

But no one has even mentioned the pure fact that the sti heads are DOHC and the NA is SOHC... would need a standalone to run it.
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Old 11-13-2012, 09:34 AM   #9
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Quote:
Originally Posted by revin-it02 View Post
But no one has even mentioned the pure fact that the sti heads are DOHC and the NA is SOHC... would need a standalone to run it.
Exactly! In the end it's just not worth the time and money to put these heads on your block. If you did end up getting them to work, you would be running turbo cams on a NA which would not help you in your search for power.

Have you looked into doing a header back exhaust, lightened crank pulley, cams, CAI and tune in your quest for more power? What mods do you currently have?
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Old 11-13-2012, 11:41 AM   #10
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^ so far I have a tsudo n1 cat back and Cosmo racing short ram intake. I haven't really been able to dump a whole lot into it just yet.

I want to put better cams and all that good stuff eventually, I just have head issues right now and I needed something that I could just drop in and have it work. I don't think that is the case anymore.

And what is a stand alone?

I was curious about the sohc to dohc and wondered if that affected it in anyway, thanks for your input
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Old 11-13-2012, 11:55 AM   #11
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Those are good mods to start with. What type of head issues are you having with your heads? Used sohc heads can be found pretty in the for sale section if you are hell bent or replacing them. Also used delta cam regrinds can be found for cheap on rs25.com and pop up quite frequently.

A stand alone ecu replaces your factory ecu and allows you to control every aspect of your EJ25 from cam control to rev limit, timing, bigger injectors, boost control, nitrous injection, and individual cylinder fuel and timing trims as an example.
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Old 11-13-2012, 12:10 PM   #12
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^ I believe I have a burnt valve on cylinder 2 intake, it makes a slap sound but only does it when it's barely under load, if its under load it runs fine. I recently adjust the valves and now I can hear where the sound is coming from better which is right over cylinder 2, my car just started to do little "hiccups" upon acceleration but nothing to major just yet..

Would it almost be easier to get the ej257 heads and block then just rebuild that? Wouldn't I have to do rear diff and transmission at the same time? because I am now adding the bigger motor and going turbo? Or could you run the ej257 n/a? Just an idea not what I plan on doing..
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Old 11-13-2012, 12:13 PM   #13
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Quote:
Originally Posted by V8Slayer

A stand alone ecu replaces your factory ecu and allows you to control every aspect of your EJ25 from cam control to rev limit, timing, bigger injectors, boost control, nitrous injection, and individual cylinder fuel and timing trims as an example.
Thanks for clarifying, I'm fairly new to ecu's and computers, I know carburetors better haha
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Old 11-13-2012, 12:25 PM   #14
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Quote:
Originally Posted by Evans2point5RS View Post
Would it almost be easier to get the ej257 heads and block then just rebuild that? Wouldn't I have to do rear diff and transmission at the same time? because I am now adding the bigger motor and going turbo? Or could you run the ej257 n/a? Just an idea not what I plan on doing..
The short answer is no, definitely not easier. To do an sti swap is gonna cost you thousands of dollars and your car will be down for some time as well. You aren't adding a larger motor but you are adding a heap more power and that can cause issues with your drive train if your not careful.

Running your sohc heads on the ej257 block is a great idea if you want to run a low/mid boost set up. It will, however, be a dog if you stay na since your compression ratio will be way too low. By the sounds of it, the cheapest route for you is just to pull the head with the burnt valve and replace it, that would save you some cash for future mods
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Old 11-13-2012, 12:36 PM   #15
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Quote:
Originally Posted by V8Slayer

The short answer is no, definitely not easier. To do an sti swap is gonna cost you thousands of dollars and your car will be down for some time as well. You aren't adding a larger motor but you are adding a heap more power and that can cause issues with your drive train if your not careful.

Running your sohc heads on the ej257 block is a great idea if you want to run a low/mid boost set up. It will, however, be a dog if you stay na since your compression ratio will be way too low. By the sounds of it, the cheapest route for you is just to pull the head with the burnt valve and replace it, that would save you some cash for future mods
Thanks for your help!

See I live in the mountains where I need a quick semi-torquey little car. Before I started having my heads issues the stock ej253 was great! If I run the ej257 block with ej253 heads will it be similar to the stock output of the ej253? And would ej22t heads have similar issues with the ej253 block?
Sorry to dump so many questions on ya

Edit: nevermind I just answered my own question thank you for your help :happybanana:
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