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Old 01-04-2015, 12:34 PM   #1
Subby2.5i
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Default EJ257 with EJ253 SOHC

Well time to start the hybrid build
Last winter I took on the project of boosting my 2007 2.5i N/A
After swapping out everything from cross-members, to the fuel system to building my own rotated setup its time to look for more power. I like challenges and doing what people say you can't, so please keep the negative comments to yourself
As of now, I picked up a 2005 STI EJ257 short block from a buddy of mine. I plan on swapping over the EJ253 SOHC heads on to the STI short blocků
Ive been digging around and trying to research around but keep stumbling on very little information. I found one member on here who said him and his wife were both running this setup and were very pleased with the results. (Im hoping he will chime in on this!)
From what I've read the SOHC heads actually flow with boost quite nicely.
From what I've read:
Near equal to or slightly better flow below 5500 rpm than DOHC heads
Less reciprocating weight therefore faster spool time
Smaller passages for increased port velocity (why they fall off after 5500)

Im basically looking for some input on this. Does anyone have an experience with this? While the heads were off I was thinking about sending the cam over to Delta for a regrind which I have heard they do very nice work! However I heard a regrind can 'throw off the flow'

As of now Im running a rotated TD-05 18G, STI header, custom up-pipe, custom down pipe with a SRS catback ( Upgrading the catback to a turbo-XS or COBB) Boomba fuel rails, 440 injectors, walbaro 255 fuel pump, Aermotive FPR, Turbo-XS front mount, Dyno tune by EFI Logics, and a HKS SSQV blow off valve.

Ill be doing some more upgrades to support the motor as well. Any recommendations would be appreciated!
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Old 01-04-2015, 08:17 PM   #2
Patrick Olsen
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Quote:
Originally Posted by Subby2.5i View Post
Any recommendations would be appreciated!
One recommendation would be to never again talk about engine stuff with whomever told you "a regrind can 'throw off the flow'," as that's utter nonsense. Well, I suppose it could "throw off the flow" if the company doing the work gave you some nonsense lobe profiles, but that would be true of brand new billet cams as well.

There's no doubt that there are gains to be had shifting from the stock EJ253 cam profiles to something more aggressive and more boost friendly. Delta Cam (among others) can definitely help you out with that, and I would bet the bang-for-the-buck will be hard to beat.
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Old 01-04-2015, 10:00 PM   #3
Subby2.5i
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Originally Posted by Patrick Olsen View Post
One recommendation would be to never again talk about engine stuff with whomever told you "a regrind can 'throw off the flow'," as that's utter nonsense. Well, I suppose it could "throw off the flow" if the company doing the work gave you some nonsense lobe profiles, but that would be true of brand new billet cams as well.

There's no doubt that there are gains to be had shifting from the stock EJ253 cam profiles to something more aggressive and more boost friendly. Delta Cam (among others) can definitely help you out with that, and I would bet the bang-for-the-buck will be hard to beat.
That's what my initial thought was too aswell! Thanks for clearing that up! I shall talk to the guys over at delta for a more boost friendly grind. Would I have to update the vavles as well to support it?
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Old 11-09-2015, 05:19 PM   #4
Kevinsmith312
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how goes this build?
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Old 11-09-2015, 07:41 PM   #5
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Well if you want to make more power hate to state the obvious but you need bigger injectors. The 440CCs arent going to let you make much more than 10-12# on that turbo before they hit full duty cycle.

The valve springs in that year head should be good for 6.5K redline without any trouble even in boost. You could get lighter retainers but I dont know what redline you are shooting for.

Great setup for making lots of torque.

I want to see some numbers when it gets tuned for high boost. I like to see people do this because everyone just says, "Just buy a WRX/STI." No need to pay the WRX/STI tax.
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Old 11-09-2015, 11:30 PM   #6
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This is my 2001 RS with a td06sl2 20g with an ej257 block and 2001 sohc heads. This was on an old hydra 2.1 for an RS, RS manifold, vishnu rails, 750 siemens, twe valve springs.



It now runs a wrx manifold and sensors, 2008 cam and crank gears, rewired for a wrx hydra unit. Haven't ran another virtual dyno on it yet but the wrx manifold swap did change the way it ran. Probably because the RS manifold runners were so small. Still running the 2001 sohc heads.
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Old 11-10-2015, 12:20 AM   #7
Subaru4you
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Default Ej257 build advice

I am considering doing this build as well. I am currently running a 03 ej251 block from a forester with ej253 heads in my 07 2.5i.
I lost some CR so I was thinking of boosting as is, but I just snagged a ej257 sti engine with burnt exhaust valves and broken ringland in one cyl for $450 came with everything but the intake. Even included the wiring harnes. So should I try and swap in the complete 257 or go hybrid as to not deal with wiring a dohc into a sohc car.
And will the stock 253 valves work under boost? I've heard the sti are sodium or something?
Thoughts or advise appreciated.
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Old 07-24-2017, 02:34 PM   #8
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So what happened with this?

Interested in 257/253 advice for taking a supercharged 253 up to say 300whp or so. The infrastructure is in place so to speak, would just need bigger fuel pump, injectors and of course, bottom end. Transmission is a concern too of course.
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Old 07-24-2017, 06:11 PM   #9
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I'm familiar with the EJ257 bottom end with the SOHC heads as we've built one. It's a torque monster.

Techwerks Engineering has pistons, cams, springs all that stuff to do what you want. This is by far the easiest way to do it mechanically.
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Old 07-24-2017, 08:38 PM   #10
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I built a EJ257(stock) bottom end/EJ251 (stock) sohc head combo earlier this year. With stock 257 pistons and headgaskets it had 185psi of compression in each cylinder.

Like mentioned above, it was a torque monster. I made 367hp/411tq on a td05h-7cm-20g turbocharger. The engine was super responsive and very fun to drive, but i shattered a piston with a WOT shift

I've moved on to a traditional dohc turbo engine setup now (ej20/25 hybrid), but i would build another sohc turbo engine in the future.
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Old 07-25-2017, 11:52 AM   #11
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Hmmmm What about EJ205 with EJ253 heads?

Why did yours crack - just too much power?

I think my Raptor supercharger is limited to about 11 PSI but not positive on that. I don't have any intention of swapping that out (Too much time and money invested there). But if only 11 pSI, it's not going to make a ton of power. I'd think around 300 Crank assuming engine starting with around 165hp. And that is with 10:1 CR. So something for me to think about. I don't need/want a $3000 IAG short block if making a whopping crank 300hp.

Last edited by pcampbell; 07-25-2017 at 12:02 PM.
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Old 07-25-2017, 11:59 AM   #12
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Originally Posted by pcampbell View Post
Hmmmm What about EJ205 with EJ253 heads?

Why did yours crack - just too much power?

I think my Raptor supercharger is limited to about 11 PSI but not positive on that. I don't have any intention of swapping that out (Too much time and money invested there). But if only 11 pSI, it's not going to make a ton of power. I'd think around 300 Crank assuming engine starting with around 165hp. And that is with 10:1 CR. So something for me to think about. I don't need/want a $3000 IAG short block if making a wopping 300hp.
205 block with 253 heads would be a bad idea because the combustion chamber is larger than the cylinder bore.

mine broke because i had it tuned very aggressively and got detonation while at full power on a pull. stock pistons ftl. but I just built the engine as a "lets see what happens" thing. i would def use forged pistons if i built anothet sohc setup
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Old 07-25-2017, 04:51 PM   #13
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Gotcha - Thanks !!
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Old 07-27-2017, 01:33 PM   #14
pcampbell
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Quote:
Originally Posted by carnz-pj-410 View Post
205 block with 253 heads would be a bad idea because the combustion chamber is larger than the cylinder bore.

mine broke because i had it tuned very aggressively and got detonation while at full power on a pull. stock pistons ftl. but I just built the engine as a "lets see what happens" thing. i would def use forged pistons if i built anothet sohc setup
I wonder if I plan for about 11 PSI supercharged on 93.. Probably somewhere around 300-340 crank HP... would I want to go with closer to stock CR pistons or more like 10:1 (like my EJ253)?

My Stock EJ253 with 6 PSI is about 180 WHP (figure 225-240 crank hp).

I'm thinking 230-240 whp with ~11 psi.

I Read something about quench height with a EJ257/EJ253-- is that an issue?

Last edited by pcampbell; 07-27-2017 at 03:06 PM.
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Old 10-07-2017, 02:51 AM   #15
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Bumping this because I've been contemplating this setup since I picked up my obs last feb.



*torque monster...
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Old 10-18-2017, 07:47 PM   #16
pcampbell
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Default EJ257 with EJ253 SOHC

So what would be max boost with a 257/253. (Stock rods and pistons) 14? 16? 18?

My issue is my sc maxes out at 11 psi. I could sell it for a vortech h67b or sci. Probably without losing money even. The 67b goes to 14psi and the bigger one to 20 or so. The v3 SCi is technically made for bigger engines but maybe it doesn't matter.

Last edited by pcampbell; 10-18-2017 at 07:53 PM.
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Old 10-03-2020, 02:16 AM   #17
terrainasaurus
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When doing a hybrid setup like this is there a paperwork process to get it legal and smogged? Say... here in CA?
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Old 10-04-2020, 07:24 PM   #18
pcampbell
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Default EJ257 with EJ253 SOHC

Quote:
Originally Posted by terrainasaurus View Post
When doing a hybrid setup like this is there a paperwork process to get it legal and smogged? Say... here in CA?


Since the 253 and 257 block is nearly identical they may not be able to tell. You should be able to tune it just as well. But what is the base vehicle?

Last edited by pcampbell; 10-15-2020 at 06:04 AM.
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