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Old 12-03-2020, 10:26 AM   #1
Morgynn96
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Default Need some hybrid motor advice!

I have a phase 1 22t block that I plan to put into my 04 WRX sedan, I am curious if I should use the heads off of my stock ej205 or I could use some 251 heads with Delta 1500 cams that's have been port and polished, I've heard the 251 heads will require modification and some wiring to make them work where as the 205 heads should work fine, also what head gasket should I be using for the 251 heads? There's a ton of info on using the 205s but can't seem to find much on the 251/ 22t hybrid, also I'm curious what injectors I should be getting to support 380-400hp? Thank you!
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Old 12-03-2020, 11:57 AM   #2
saaiello21
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Sorry I dont know much about the 22t block I do remember seeing either of those heads should mate up but the 205 heads may make the compression ratio too high. For 380 to 400hp I would go with no less then 850cc injector. 1000cc would be better to give some headroom for future upgrades.
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Old 12-04-2020, 11:35 AM   #3
subaru_gc8
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i believe with the 205 heads it bumps the compression up to around 9ish the 2.5 heads wont work and the work you put into them would not be worth the gains. What would be really cool is for you to find a set of jdm heads with avcs and hook that up that would be awesome
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Old 12-04-2020, 03:59 PM   #4
pcampbell
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The easiest thing will always be to keep your stock heads.

Try this video, although it applies to a EJ25 block and EJ20 heads.

For injectors - what fuel are you using?

Last edited by pcampbell; 12-04-2020 at 04:57 PM.
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Old 12-06-2020, 09:06 PM   #5
Morgynn96
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Quote:
Originally Posted by subaru_gc8 View Post
i believe with the 205 heads it bumps the compression up to around 9ish the 2.5 heads wont work and the work you put into them would not be worth the gains. What would be really cool is for you to find a set of jdm heads with avcs and hook that up that would be awesome
I actually have a jdm ej205 with avcs that I would be taking out of the WRX,why would the 251 heads not work?
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Old 12-06-2020, 09:07 PM   #6
Morgynn96
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Quote:
Originally Posted by pcampbell View Post
The easiest thing will always be to keep your stock heads.

Try this video, although it applies to a EJ25 block and EJ20 heads.
What is a Subaru/WRX Hybrid Swap? - YouTube

For injectors - what fuel are you using?
I am fr Calgary Alberta Canada so we have 93 octane, some places 94
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Old 12-07-2020, 09:17 AM   #7
theotherguy
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Did this 12 or 13 years ago. You’re going to be low, like 7.7 or so with a .058 gasket and sohc heads if I remember right. We did k heads on a 22t with 47cc combustion chambers. There are some good threads about this out there.
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Old 12-07-2020, 11:38 AM   #8
subaru_gc8
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Quote:
Originally Posted by Morgynn96 View Post
I actually have a jdm ej205 with avcs that I would be taking out of the WRX,why would the 251 heads not work?
cause your dealing with a 92mm bore and a head that is meant for a 99.5mm bore. you will have 8.5mm of your chamber being too big for the bore on the head side and you will have a weird chamber overlap between your heads and your cylinder bores.
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Old 12-07-2020, 06:40 PM   #9
theotherguy
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Throw a used head gasket on the ej22 and see if it'll clear or measure your 251 combustion chamber and see if they'll fit inside of the 97mm bore. You'll also need to figure out what coils you are going to use. Some are using newer NA COP and install a stud in the covers to mount them. My 2001 RS ej257 with 251 head set up is using GM LS coils mounted on brackets with short custom wires, I also run WRX manifold and sensors.

Last edited by theotherguy; 12-07-2020 at 06:43 PM. Reason: spelling
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Old 12-09-2020, 02:08 PM   #10
monkeyposeur
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I run an EJ22T with 205 heads that I chamber matched to the 22T bore. You can see my build thread here: https://forums.nasioc.com/forums/sho....php?t=2696523

I really like the setup and put down around 350-360 whp with a Blouch 20G-XT.

For injectors you should be fine with some DW 1050s.
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Old 12-12-2020, 11:57 PM   #11
Morgynn96
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Quote:
Originally Posted by subaru_gc8 View Post
cause your dealing with a 92mm bore and a head that is meant for a 99.5mm bore. you will have 8.5mm of your chamber being too big for the bore on the head side and you will have a weird chamber overlap between your heads and your cylinder bores.
I'd be using the 22t block not the 2p5 block
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Old 12-12-2020, 11:57 PM   #12
Morgynn96
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Quote:
Originally Posted by theotherguy View Post
Throw a used head gasket on the ej22 and see if it'll clear or measure your 251 combustion chamber and see if they'll fit inside of the 97mm bore. You'll also need to figure out what coils you are going to use. Some are using newer NA COP and install a stud in the covers to mount them. My 2001 RS ej257 with 251 head set up is using GM LS coils mounted on brackets with short custom wires, I also run WRX manifold and sensors.
What would you recommend I do in that case?
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Old 12-13-2020, 11:40 AM   #13
theotherguy
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Quote:
Originally Posted by Morgynn96 View Post
What would you recommend I do in that case?

Coil on plug would be easiest as you wouldn't have to modify your harness much and wouldn't have to change the dwell in your ecu.

Ultimately I'd recommend monkeyposeur's build thread, it's a tried and true recipe for awesomeness or sell the block and buy another JDM engine.
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Old 12-15-2020, 11:38 AM   #14
subaru_gc8
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Quote:
Originally Posted by Morgynn96 View Post
I'd be using the 22t block not the 2p5 block
uhh okay you have a 97mm with a overlap on your heads of 2.5 mm
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