Id really like to see a video showing the differences in the RA heads N casting, that have avcs on all 4 cams i cant find anyone talking about them at all. Great video thank you for the thorough explanation!
Thanks for your question. They are basically the same as the W25 heads which are the dual AVCS STI heads. We have looked at the N25 castings and at least as far as we can tell, there is no significant difference between them and the W25 heads. Hope that helps and Stay Tuned!
Thanks for the video, very informative and all my questions have been answered, I am mid hybrid swap build and I think I will just put 2.5 heads on 2.5 block, JE pistons and Chamber matching is still risky for me haha.
When we first started building these hybrid swaps years ago, E85 was nowhere near as available as it is now at the pump. Id like to do a high compression engine with E85 to see how it would perform.
I bought a replacement ej255 (eudm) once and got sent an ej205 (jdm) I didnt actually realize and fitted the engine, only to realize that the sensors didnt match up at all. things that are the same are different, avcs has a slightly different bolt location for the solenoids. The crank position sensor wheel is the same, but clocked different on the crank, the cam position sensors arent even usable, etc. With the stock ej255 ecu. Despite the ecu getting incorrect crank position data and basically no cam position data. It still started and ran, which is kind of amazing, as it really shouldnt have worked at all. It absolutely threw petrol out of the exhaust though, but god damn did the boost come in HARD. Obviously it was a ticking time bomb, and essentially would never have got me the 200 miles home that i needed it to. I finally realized and sent it back and got a correct engine. However, its something ive wondered about ever since. Actually downgreading to a 2.0 block and leaving everything else 2.5 and stock. Always wondered if you would get a power boost over just the 2.5 block. It certainly felt way more aggressive to drive, the boost coming on was like an on off swtich with barely any discernable spool up. if i had the funds and the time, its something id love to revisit.
Im running 9:1 on 92oct built block. At 20psi no knock events tune is solid. Of boost response is worth the reduction in psi imho. My turbo is larger more efficient and biggest TMIC
can anyone tell me what the Benefit of the Hybrid swap is? I can find 100's of threads on how to do one but No one ever say WHY? Why spend more money on the 2.5 ?
Thanks for your question Trip. The simple answer is the extra displacement. Since the cost of a new shortblock is pretty much the same, people very quickly figured out that they could put in the 2.5 liter block with their 2.0 heads and the hybrid swap was off and running. There are certainly some things to consider with the swap, and that is what we go into in this video. It really all comes down to power goals, and desired power band, etc. Thanks for watching!
I've been trying to figure out the same thing for my subie. From my understanding its really practical for non 2.5 cars, because you don't have to swap the wiring harness and can up the displacement. I think the ej20 has a better head design too so that gives the engine a more refined power band.
I wonder if this is what I got on my build . I bought an 05 Wrx Station wagon and the previous owner I bought it from didn’t know what was done to it he said it was rebuilt but when I look at the block where it says the ej20/25 it says ej25. I know wrx are ej20 and I wonder if i have this built. It has an sti intercooler with regular throttle cable not the electronic one. The turbo doesn’t look oem it looks alittle bigger than oem. I also can hit 20 psi for some reason.
Thanks for watching and thanks for your question. If the marking on the shortblock itself say EJ25, then there is a good likelihood that an EJ25 block was used with the 2 liter cylinder heads as we discuss in this video. If you can take the car to an experienced Subaru shop, they may be able to give you more insight as to what has been done with a quick look at the car. Hope that helps and Stay Tuned!
I know you mentioned the cosworth 1.5mm gaskets. I have some 1.3mm gaskets wondering if that would balance out the compression? Ej257 with stock cylinder heads. I had ran the stock ones for a little and eventually overheated. New block as well😅
Thanks for your question. 1.3mm would get you close certainly. Roger Clark Motorsports now makes the 1.5mm as Cosworth isn't making them any longer. www.flatironstuning.com/rcm1691 Thanks for watching and Stay Tuned!
Just wanted to say thanks for these videos - for some reason (not sure exactly why...) it's difficult to find informed technical opinion for Subaru turbo engines.
@@KDD8 Well, just enough to know that many of their aspects are different than the EJ20 that we got here. We haven't played with one yet, but the fact that it is a factory closed-deck 2.0 liter is pretty interesting.
@@KDD8 Okay, given that, the fact that you have an EJ20K shouldn't have too much of an effect on how you tune it. An Access Port for the USDM WRX would work for instance. I believe that the 20K's had a higher compression ratio than the US Spec 8.0:1. If it does have a bump in compression, you need to be careful adding timing, especially if you are tuning on pump gas. If you can work with an experienced Subaru tuner, I'd say that would be ideal. Hope that helps, and let me know if there is anything else I can do.
So I have a 2004 WRX recently developed a rod knock what's the lot of your videos they are very great and informal I have a question so if I use the 2.5 short block with a 2.0 heads and do the thick head gasket will the car start and run I have a Cobb accessport on a stage 2 tune for the 2.0 will the accessport still work on the 2.5 hybrid
Thanks for your question Brett, and sorry to hear that you are having trouble. The short answer is that you will have to get your car tuned for the extra displacement, but since you have an Access Port, there are a number for tuners out there that can help you with that. Good luck getting your car back up and running, and please feel free to reach out to us if you need anything else.
Thanks for your question. The short answer is I don't know how well the EJ20G heads would work on an EJ257 block. I believe that they have a smaller combustion chamber, and the coolant passages are definitely different, so a head-gasket might be challenging too. This hasn't come up in the shop so I don't have any first hand experience. I'd recommend starting off by checking the combustion chamber volume of the heads and then to compare the EJ257 head-gaskets with the heads to see if you would get decent coolant flow to the heads. Hope that helps and Stay Tuned!
Thanks for watching and thanks for the question. Your compression is going to drop well below 8:1 if you have the hybrid pistons with the deeper dish and the thicker head gaskets. If possible I would recommend just using the stock thickness head gasket as that is what those pistons are designed around. Hope that helps and Stay Tuned!
I love this channel, thanks for explaining this. I had a couple of questions but i was reading those asked prior so many got answered. I have an 04 WRX, that i am going to use as my platform. I was thinking of doing the hybrid because of this reason. I now know, that because of the chasis, i should use all parts meant for that 04 chasis. What i wanted to ask is when i do the hybrid swap. Would it be recommended to get the 6 speed out of an STI? Im looking for big numbers and am concerned about the drivetrain.
Thanks for your question. If you are trying to make more than 350 whp, then yes, the 6-Speed is the most reliable way we have found to hold the power. And you get the added benefit of a front torque-biasing diff, and the DCCD center diff. We have done a video on that swap too if it helps. th-cam.com/video/nUJ7E2Bh5g0/w-d-xo.html th-cam.com/video/uf4tcG5GqDU/w-d-xo.html Good luck with the swap, and Stay Tuned!
@@FlatironsTuning thanks for the links. Im getting all my parts list done. I want to be able to have what i need and no get lost when it comes time. Would you recommend the mooressport rear and front subframe, if i were to try to use the Sti axels
Is this applicable to adm I have a blown ej205 it's impossible to find a ej207 unless your prepared to wait.Will my Forester gt heads bolt straight on to a ej25 block what else would need to be done
Thanks for your question. Yes, your Forester EJ205 heads will bolt right up. But I would recommend double checking that the cylinder head volume of your heads is close to, or the same as the USDM EJ205 heads. I suspect it is, but you would want to confirm that. Hope that helps and Stay Tuned!
Thanks for your question. Yes, all of the hybrid options are designed around the STI piston, so that would be the best place to start. Thanks for watching and Stay Tuned!
I understand that some pistons come with a higher dome. Would a piston with flat surface or a slight deeper dish work without having to buy hybrid pistons?
Thanks for your question. These pistons all have dished tops. The depth of the dish is what is used to control compression, so the hybrid piston has a deeper dish than the standard piston. I hope that helps, and Stay Tuned!
Wouldn't it make sense to have the higher co mlm pression for someone who wants to run a higher compression n/a 2.5l? I want to go outside of the normal Subaru "turbo" and make a performance si gle cam ej25 in my 06 forester.
Sure, if you are wanting to build an N/A Subaru engine, you will definitely want more compression. I'd recommend you look into what the Open Light Rally guys are doing. They have to run a 2.5 liter N/A engine in that class, and they are getting them up to roughly the 2.0 liter EJ stock power level, which is pretty cool. They are adding compression, tuning, and cams for the most part I believe. If you can, take a look at Ecotech. They are having some good success with that formula. Thanks for the comment and Stay Tuned!
Hello can you give a rough guideline for safe power for the 1.5mm head gasket, piston and chamber matching. Like how many kws or hp or psi is it safe to run at
Thanks for your question. If you are running the 1.5mm gasket, it is more ideal if you are running less than 20 psi of boost and shooting for less than about 375 whp. If you want to make more boost pressure or power than that, a stock thickness HG is better. Hope that helps and Stay Tuned!
Thanks for your question. We haven't done that ourselves, but it seems to be more common. A lot of the components of the EJ20X are unique (like the turbo for instance), so the swaps seem to end up being much more complicated than it would seem at the beginning. Getting the Dual AVCS to work would also be an issue, and if you just wanted single AVCS, you still have the problem where the pickup's on the cams are opposite of what the USDM computer is looking for. You may want to take a look at our JDM swap video as well: th-cam.com/video/3ZwcQRsUI2M/w-d-xo.html Hope that helps, and Stay Tuned!
Hey bro.. in nz the ej20x is mounted to every legacy gt 2.0 from about 03 to 08, 09 maybe but I could be wrong.. Anyway.. ive got that motor in both my legacy and S-GT (which is just a GH8 WRX), but there is a difference.. theres the ej20y, which comes in the manual variations, like of course the WRX.. that motor pumps out an xtra 20bhp more then the 20x but again thats only because of the transmission being an auto.. Key things to know, its a twinscroll turbo. Do your homework on them.. if its a "JDM" then try to gun for the jdm computer and all that aswell.. then u can retain the avcs, if you want.. and other things like its ability to be reflashed.. All in all, the motor is amazing.. infact id say one of subarus better ones..
Hi! This may sound like a dumb question but if I buy new head castings for a ej205 that has chamber matched to the ej257, can I run regular forged 2.5 pistons? Would that change the cpr? Or since I did the chamber match the cpr doesn’t change?
Thanks for your question. Yes, as long as you have the correct volume in the cylinder heads, you can run a stock thickness headgasket because your compression ratio will be correct. That being said, if you are looking at getting new EJ205 castings chamber matched, you should also look at simply using EJ25 heads. That is also an option, and we have a video going into detail about that here: th-cam.com/video/6Xzopgayw7c/w-d-xo.html Thanks for watching and Stay Tuned!
Thanks for your question. I'd say that 400 whp, or say 20+ psi of boost is where the 1.5mm head gaskets are not ideal. Hope that helps and thanks for watching!
Thanks for your question. I do not. The later EJ205's that we got here had the cross-drilled EJ207 crank, so there is no question that part crosses over. The bore is the same, so all of the 207 pistons would work, and I believe that the rods are interchangeable as well. Really, the difference comes down to the case itself, which is open-deck on the 205, and semi-closed on the 207. I hope that helps and Stay Tuned!
can you do a video on the avcs systems, im a mechanic coming up and im doing a new engine on a wrx, the one for the car is a single new one is a duel , thought about making my own system for the duel
Got a question, not exactly a 2.0/2.5 hybrid but sort of along the same lines. I have a supercharged EJ253 and I am rebuilding a spare motor. I'm wondering if the heads are decked, can I get away with 1mm shorter rods (STI 130.5mm rods vs the stock NA rods 131.5mm rods ) rather than a thicker HG? Will I run into issues with quench and combustion? I guess it would depend on how much material is removed?
Thanks for your question. You could certainly do that. The D25 heads have a smaller combustion volume, so you would get a slight bump in compression with that pairing. If you run a 1.1mm thick headgasket, that would correct the compression to about 8.4:1. I'd recommend going through our video on the B25 Vs. D25 heads if you haven't all ready: th-cam.com/video/h6FdnJRWa6o/w-d-xo.html Hope that helps and Stay Tuned!
So other than displacement. Is this a better way to make a lot power? Is it more reliable compared to making more power with just a 2.0 block and head?
Thanks for your question. The short answer is that yes, any power goal over about 300 whp will be easier with the extra displacement of the 2.5 liter engine, and that is the appeal. For instance, our 03 WRX project car with the 2.5 liter conversion is making a little over 300 whp on a 20G with a stock block and at only 18 psi of boost. To get a 2.0 to make 300 whp, you have to push much harder, and you will not have any where near the low-end torque of the 2.5. Now that being said, of course there are people making lots of power on 2.0 engines too. Everything has to work together on the build, and you do have to push a pretty big turbo with a decent amount of boost, but it can be done. I wouldn't like to daily drive it though :-) If you are trying to decide between the two, you have to look at your power goals, your budget, and how much of a powerband you want, and where you want the power to come on. Then compare a 2.0 build and 2.5 build and see which one checks the most boxes :-)
I just had my 06 OBXT block crack at 147k. I replaced the head gasket and used ARP bolts but I still got overheating and air in the heater core. Flushed heater core skimmed head cleaned up block still overheating. Vacuum tested the cooling system and it will not hold vacuum. I want to do a used 257 block but is there any advantages? Or will the 255 block be ok to use? New forged pistons/rods, etc. I am new to this platform so is there a recommendation of what size to bore to? TIA!
Thanks for your question. First, definitely take a look at our blog talking about the differences between the EJ255 and EJ257: www.flatironstuning.com/blog/what-is-the-difference-between-an-ej255-and-an-ej257 Then look at our video that talks about the difference between D25 and B25 heads. th-cam.com/video/h6FdnJRWa6o/w-d-xo.html The short answer is that you should have B25 heads on your Outback, so the STI block is actually what you had to start off. Hope that helps and good luck with the re-build!
@@FlatironsTuning Thanks I didn't know you ha a video on the heads too but I saw the one on the blocks and pretty much the internals are the only difference between the two. Thanks
My question is what’s the ideal hp that you could be running with the thickness heads gasket? No for a tracking car but could you some race one a time? I am planing on doing a hybrid swap
Thanks for your question. I would say that if you are planning on making more than 400 whp, or running more than 20 psi of boost, then the double thick head-gasket would not be an ideal way to go. For what it is worth, they are just more prone to failure because they are twice as thick as stock. I hope that helps and Stay Tuned!
So I bought an '02 that was OEM 2.0L turbo, and then the shop told me the prior owner had put in a 2.5L block. What's the best way for me to know which method he used? I'm assuming I could see a 1.5mm head gasket, but what if he machined the heads or put in different pistons or put the 2.5L heads on it? I'd like to know what I've got as a starting point. I have a cheap bore camera if I could put it down a spark plug hole.
Thanks for your question. That is a tricky question. Can you contact the previous owner at all? You can try to measure the thickness of the HG that you can see as a starting point, but it wouldn't be a 100% certainty. Really, a lot of that information you could only find out by tearing the engine down. JE Hybrid pistons for instance pretty much look the same, they just have a deeper dish when you measure them. I'd say that as long as the engine is healthy and running well, I wouldn't worry about it too much. Just run the car, and if you decide that you want to do a bigger build, it may be worthwhile to do an actual tear-down to see what you have. Good luck, and let us know if you have any other questions!
Hi, I'm struggling to figure out what head gasket to use? I have an 08 ej255 block with sti t20 2.0 heads. A guy from cometic mentioned I need to use a gasket that suits the coolant passages? When CC'ing pistons and combustion chambers it is only going to be 8.5:1 So I'm thinking of just running a stock gasket.
Hey men, cheers from Panama (The country XD). I'm planning on doing a short block swap on my USDM wrx 2005. Do you think I'm going to be able to get some whp between 300 and 350? (Adding tune, turbo and other stuff, but keeping the internals of the shortblock stock)
Thanks for your question. If you are keeping with the 2.0 liter, it is going to be tough to get over 300 whp. The most common turbo on the 2.0 to hit that power level is something like a 20G, or maybe a Blouch Dom 1.5 XTR. The problem is they will be very peaky powerbands, and you may have to try to rev higher to give you more useable power. And on a stock shortblock, that can be problematic. Now, if you do the hybrid swap with a 2.5 shortblock, you should be able to hit at least 300 whp with either of those turbo options and have a lot more useable power. I hope that helps, and good luck with your build!
So, which option do you think is the best one to get those 300-350 whp I want to have (as reliable as possible as it is my daily day drive), - Swap my current shortblock from WRX to STI's, and just follow your guidance on the video. Side note, I think if I choose this option I would go with the thicker head gasket, as I would rather prefer to keep the new STI shortblock unopened here in Panama. - Or, Just buy new forged Pistons, forged Rods, Rings, and basically rebuilt the internals but keep the actual shortblock stock.
If your goal is to hit the 300 - 350 whp mark while stressing the engine as little as possible, then the 2.5 liter is your best bet. Simply put, you have to wind out a 2.0 more, or push a lot more boost to hit that same mark compared to a 2.5 liter engine. I actually had basically the same goal that you mention , and that is why I ended up going with a full 2.5 liter longblock swap :-) My goal was to make 300 whp as reliably as possible to have a fun and reliable track car. We did a video on that too if you haven't watched that yet :-) th-cam.com/video/6Xzopgayw7c/w-d-xo.html
Thanks for your question. That is not possible. With that combination, there wouldn't be a headgasket that would work, and it would also have a pretty bad combustion chamber design. Hope that helps and Stay Tuned!
Thanks for your question. If you have JDM STI heads, the approach for installing them to a 2.5 liter block is the same as we detailed here. Hope that helps and Stay Tuned!
Thanks for your question. Basically, you would want a 1.5mm thick head gasket if that is what you are going to use to correct the compression ratio. At this time, the best option would be the Roger Clark 1.5mm HG. Here is a link to those on our site: www.flatironstuning.com/rcm-mls-single-head-gasket-1-5mm-04-06-ej25 Hope that helps, and Stay Tuned!
I just picked up a ej257 block and am wanting to install my 253 heads. If i want to keep my current CR do i just use the 253 rods and pistons or does it really matter?
Thanks for your question. If you do want to keep your compression ratio, yes, you need to at a minimum use your pistons. The NA engines have a higher compression ratio, and that largely comes down to the the piston dome an cylinder head shape. If you stay with a turbo piston, then your compression will most likely drop a good amount. I hope that helps, and thanks for watching!
Thanks for your question Carlos. We have actually put together 3 different levels of kits for the Hybrid swap. Here are links to those on the sight. It will give you a good idea what the cost of the swap would be: www.flatironstuning.com/p-1896-basic-25l-hybrid-swap-install-kit.aspx www.flatironstuning.com/p-1898-comprehensive-25l-hybrid-swap-install-kit.aspx www.flatironstuning.com/p-1899-master-25l-hybrid-swap-install-kit.aspx I hope that helps, and please let us know if you have any other questions!
So the one thing I still don't understand is why would you even want to do a hybrid swap? What does this even accomplish? Does it make it easier to make more power or something? But if your swapping in a 2.5 liter engine why even bother with the smaller engine heads...
Thanks for the question. Yes, you get a big bump in torque with the larger engine, and that extra displacement does make it a lot easier to achieve higher power goals. As for why you would keep the EJ20 heads, the answer is generally that if they are in good shape, it reduces the cost of the engine swap by a good deal. Thanks for watching and Stay Tuned!
@@FlatironsTuning Oh thanks for the info, I already have a EJ255 but it's the 05 version which is essentially a EJ257. What would you recommend to do if I want to get around 350 hp out of it
Thanks for your question. Since you are just putting in an STI Block, your parts choice would be for the WRX. Specific to the TGV's, since you are moving the TGV's from the WRX over, you would just get TGV deletes for a WRX.
Thanks Keith. Those are just Subaru Shirts that we have acquired through the years. I Don't believe that they are still making that one, but I'll check.
Thanks for your question. This would not really work on an NA EJ25. They start off with higher compression all ready, and there would be less gains from putting on a smaller cylinder head, and a lot more issues due to piston shape, etc. If you want to make more power with the 2.5 Liter take a look at what the Open Light Rally guys are doing, and maybe reach out to EcoTec. They have developed some great engine packages for the Rally teams: ecotechimportauto.com/ Hope that helps, and Stay Tuned!
Thanks for your question. No, you would need one or the other. Since the JE pistons have a deeper dish, that corrects the compression ratio, so you can then run a standard thickness headgasket. Thanks for watching and Stay Tuned!
Thanks for your question Bob. We haven't worked with a naturally aspirated build at this point, so I can't offer much guidance. I have heard of putting on phase 1 2.5 DOHC heads on the NA blocks, etc., but I can't tell you much more than that. You'd want to look at compression ratio, and how the heads mate up to the pistons that you are using as a start, and go from there. I'd recommend talking to ASF Machine, as they have worked a bit with building 2.5 liter NA engines, and they would be a better resource than we are at this time. Thanks for watching!
@@FlatironsTuning yall interested in seeing how it goes with ej251 sohc heads on the 257 block with the sti headgaskets I believe it will be a 9:1 motor and I will be pushing 5-10psi through it. I am currently looking for a 257 short block so I may have to grab the one you guys have. Would love to chit chat and figure some stuff out.
Hey Flatirons..great video. I know i'm a little late to the conversation but i'm looking to do the opposite. I'm interested in changing my forester 2.5l turbo ej25 engine for an ej20 2 litre (with alu manifold). I've heard it can be done with little modification ....btw...i know absolutely nothing about mechanics but just want my car to get running again and the ej25 engine is very hard to find. thanks
The thing to consider with high compression would be maintaining an optimal combustion chamber shape. The simple hybrid swap will bump your compression if you use the stock thickness headgaskets, but there is a lot of overhang from the heads, and not ideal quench area between the piston and cylinderhead. Ideally, you would want to either chamber match your 2.0 heads, and then run a higher compression 2.5 piston, or run a higher compression JE Hybrid piston, which is designed to match up to the 2.0 combustion chamber. If you are going to run a detonation resistant fuel like E85, this is much less of an issue. If you are thinking of running pump gas, I'd say that you would want to stay pretty close to stock compression ratio. Hope that helps, and good luck with your build!
Higher compression and you will crack the piston. Subaru engines aren't good for high compression as they low compression engines from factory vs say VW golf gti or r.
Any idea what displacement would be if you had a ej25 block/crank with Ej207 rods and head? standard combustion chamber. Does the rod length make much of a difference?
Thanks for your question. So putting a 2.0 liter crank in a 2.5 liter case has been done by a number of shops, and is considered a De-Stroker build. It is a bit of a deep topic, but here are the cliff notes. Your displacement will drop to 2.3 liters, and if you use the standard STI rods, your compression will drop to about 7:1 aproximately. This is one of the origins of the +2mm rods. If you use the +2mm rods with standard STI pistons, it will bring the pistons back up to standard height, and then you have all of your standard compression ratios. Manley does make a De-Stroker piston, so that you can use standard length rods and get the pistons to the correct height, but there are definitely some benefits from going with a longer rod. If you search for a STI De-Stroker Build, or a 2.3 liter Build, or an STI Long Rod build, that should get you some more good information. Just don't get confused with putting a 2.5 liter crank in an older EJ22 case. That is another route to a 2.3 liter built but it is entirely different :-) Hope that helps and feel free to call us if you have any more questions!
Thank you for the response! The +2mm rod = ej25 rod? I'm now onto my second build... first one didn't last as long as I hoped but was a lot of fun while it did! I did notice one the first build that there was excessive piston to deck clearance. I want to eliminate this for the next build.
Hello BigBear. Was this a de-stroker build? If you used a standard length rod, that would put the piston well below deck height, and lower your compression a lot. The +2mm rod I mentioned is something that has to be custom made. There are a few companies out there that can produce them. We can get them from Pauter for instance. Hope that helps, and good luck with the next build!
If you are doing a Hybrid build, you must run 2.5 liter head gaskets. If you are using the JE Hybrid Pistons, then the stock thickness head gaskets will be what you need. Good luck with your build!
@@AntoineVirgo The JE Hybrid Pistons are designed to give you a compression ratio of 8.5:1 with the 2.0 head. If you want more detailed information about the pistons, here is a link to JE's site with all the info you could want: www.jepistons.com/Catalogs/Sport-Compact/Subaru/ej257_ej20head.aspx Thanks, and Stay Tuned!
Most head gaskets will work with larger bores. The only ones that don't from what we have seen are JE and Cometic, however, they do work on both 99.5mm and 99.75mm bores. You only need a different gasket if you go up to 100mm.
FlatironsTuning Hey guys, I see you do a lot with turbo engines. I know a lot of us over here on the N/A Subie side would love/really need a video on an N/A hybrid or frankenmotor, as they're known. 2.2 heads on a 2.5 block, 11.0-11.5:1 compression (I don't know the exact number), cams, porting and polishing-everything to make an angry N/A. There's a need for a pretty much all around video explaining everything we need to build it, what to do, what not to do, etc. There are a few build threads scattered about the various forums, but a lot are vague and/or not very detailed. It would help to clear up the confusion, and I know I could certainly use it as that is my current goal for my '99 BG5 5MT wagon.
Thanks for the suggestion! We don't do much with that, but it is something that we will keep on our list. I'll tell you that one of the guys we sponsor is Racer Dave - Dave Brown. His car is an Open light rally car, so a 2.5 liter N/A engine. Some of those guys are starting to figure out some things on making N/A power, and I know that Dave has some things in store. I'd be worth checking out his channel as well :-)
Hair line cracks at the spark plug holes is quite common on early JDM EJ207 version 7 8 9 heads , know of engines still going strong with no issues
Thanks! That answered my question! I’ve always heard about hybrids but I didn’t know wtf I mean. I knew they don’t make electric Subaru’s lol!
Neighbour's wish they were hybrids tho🤣🤣
You guys are awesome. Thank you for making this video.
Thanks Jay!
Business in the front party in the back. Nice..
Id really like to see a video showing the differences in the RA heads N casting, that have avcs on all 4 cams i cant find anyone talking about them at all.
Great video thank you for the thorough explanation!
Thanks for your question. They are basically the same as the W25 heads which are the dual AVCS STI heads.
We have looked at the N25 castings and at least as far as we can tell, there is no significant difference between them and the W25 heads.
Hope that helps and Stay Tuned!
Thanks so much Flatironstuning🤝
Absolutely! Thanks for watching and Stay Tuned!
Thanks for the video, very informative and all my questions have been answered, I am mid hybrid swap build and I think I will just put 2.5 heads on 2.5 block, JE pistons and Chamber matching is still risky for me haha.
Very glad that the video was helpful.
Thanks for watching and Stay Tuned!
When we first started building these hybrid swaps years ago, E85 was nowhere near as available as it is now at the pump. Id like to do a high compression engine with E85 to see how it would perform.
High compression on E85 is definitely interesting. But only on E85 ;-)
Thanks for watching and Stay Tuned!
I bought a replacement ej255 (eudm) once and got sent an ej205 (jdm)
I didnt actually realize and fitted the engine, only to realize that the sensors didnt match up at all.
things that are the same are different, avcs has a slightly different bolt location for the solenoids. The crank position sensor wheel is the same, but clocked different on the crank, the cam position sensors arent even usable, etc.
With the stock ej255 ecu. Despite the ecu getting incorrect crank position data and basically no cam position data.
It still started and ran, which is kind of amazing, as it really shouldnt have worked at all.
It absolutely threw petrol out of the exhaust though, but god damn did the boost come in HARD.
Obviously it was a ticking time bomb, and essentially would never have got me the 200 miles home that i needed it to. I finally realized and sent it back and got a correct engine.
However, its something ive wondered about ever since.
Actually downgreading to a 2.0 block and leaving everything else 2.5 and stock. Always wondered if you would get a power boost over just the 2.5 block.
It certainly felt way more aggressive to drive, the boost coming on was like an on off swtich with barely any discernable spool up.
if i had the funds and the time, its something id love to revisit.
Im running 9:1 on 92oct built block. At 20psi no knock events tune is solid. Of boost response is worth the reduction in psi imho. My turbo is larger more efficient and biggest TMIC
can anyone tell me what the Benefit of the Hybrid swap is? I can find 100's of threads on how to do one but No one ever say WHY? Why spend more money on the 2.5 ?
Thanks for your question Trip. The simple answer is the extra displacement. Since the cost of a new shortblock is pretty much the same, people very quickly figured out that they could put in the 2.5 liter block with their 2.0 heads and the hybrid swap was off and running.
There are certainly some things to consider with the swap, and that is what we go into in this video. It really all comes down to power goals, and desired power band, etc.
Thanks for watching!
Trip SkyWalker
The 2.5 will give u more torque, which the 2.0 lacks
I've been trying to figure out the same thing for my subie. From my understanding its really practical for non 2.5 cars, because you don't have to swap the wiring harness and can up the displacement. I think the ej20 has a better head design too so that gives the engine a more refined power band.
Can you do a video on ej257 with ej207 jdm big port heads?
@@FlatironsTuning do the ej205 heads out flow the ej257?
I wonder if this is what I got on my build . I bought an 05 Wrx Station wagon and the previous owner I bought it from didn’t know what was done to it he said it was rebuilt but when I look at the block where it says the ej20/25 it says ej25. I know wrx are ej20 and I wonder if i have this built. It has an sti intercooler with regular throttle cable not the electronic one. The turbo doesn’t look oem it looks alittle bigger than oem. I also can hit 20 psi for some reason.
Thanks for watching and thanks for your question.
If the marking on the shortblock itself say EJ25, then there is a good likelihood that an EJ25 block was used with the 2 liter cylinder heads as we discuss in this video.
If you can take the car to an experienced Subaru shop, they may be able to give you more insight as to what has been done with a quick look at the car.
Hope that helps and Stay Tuned!
I know you mentioned the cosworth 1.5mm gaskets. I have some 1.3mm gaskets wondering if that would balance out the compression? Ej257 with stock cylinder heads.
I had ran the stock ones for a little and eventually overheated. New block as well😅
Thanks for your question. 1.3mm would get you close certainly.
Roger Clark Motorsports now makes the 1.5mm as Cosworth isn't making them any longer.
www.flatironstuning.com/rcm1691
Thanks for watching and Stay Tuned!
Just wanted to say thanks for these videos - for some reason (not sure exactly why...) it's difficult to find informed technical opinion for Subaru turbo engines.
Glad we could be of help, and thanks for watching!
@@FlatironsTuning Are you familiar with EJ20K motors?
@@KDD8 Well, just enough to know that many of their aspects are different than the EJ20 that we got here. We haven't played with one yet, but the fact that it is a factory closed-deck 2.0 liter is pretty interesting.
@@FlatironsTuning I have an EJ20K motor with EJ205 heads, intake manifold, and ECU but not sure how I should be tuning it. Thats all. Thanks
@@KDD8 Okay, given that, the fact that you have an EJ20K shouldn't have too much of an effect on how you tune it. An Access Port for the USDM WRX would work for instance.
I believe that the 20K's had a higher compression ratio than the US Spec 8.0:1. If it does have a bump in compression, you need to be careful adding timing, especially if you are tuning on pump gas.
If you can work with an experienced Subaru tuner, I'd say that would be ideal.
Hope that helps, and let me know if there is anything else I can do.
So I have a 2004 WRX recently developed a rod knock what's the lot of your videos they are very great and informal I have a question so if I use the 2.5 short block with a 2.0 heads and do the thick head gasket will the car start and run I have a Cobb accessport on a stage 2 tune for the 2.0 will the accessport still work on the 2.5 hybrid
Thanks for your question Brett, and sorry to hear that you are having trouble. The short answer is that you will have to get your car tuned for the extra displacement, but since you have an Access Port, there are a number for tuners out there that can help you with that.
Good luck getting your car back up and running, and please feel free to reach out to us if you need anything else.
I was thinking about doing the exact same thing if that event ever occurred or when the car felt slow again haha do did you ever go through worky that
Great video. Does this also apply to ej20G heads ? I have a v2 sti and am looking to fit an ej257 short block ?
Thanks
Thanks for your question. The short answer is I don't know how well the EJ20G heads would work on an EJ257 block. I believe that they have a smaller combustion chamber, and the coolant passages are definitely different, so a head-gasket might be challenging too.
This hasn't come up in the shop so I don't have any first hand experience. I'd recommend starting off by checking the combustion chamber volume of the heads and then to compare the EJ257 head-gaskets with the heads to see if you would get decent coolant flow to the heads.
Hope that helps and Stay Tuned!
I have the Je hybrid pistons and a 1.5 mm head gasket can someone tell me what the compression will drop too and will it be applicable?
Thanks for watching and thanks for the question. Your compression is going to drop well below 8:1 if you have the hybrid pistons with the deeper dish and the thicker head gaskets.
If possible I would recommend just using the stock thickness head gasket as that is what those pistons are designed around.
Hope that helps and Stay Tuned!
I love this channel, thanks for explaining this. I had a couple of questions but i was reading those asked prior so many got answered. I have an 04 WRX, that i am going to use as my platform. I was thinking of doing the hybrid because of this reason. I now know, that because of the chasis, i should use all parts meant for that 04 chasis. What i wanted to ask is when i do the hybrid swap. Would it be recommended to get the 6 speed out of an STI? Im looking for big numbers and am concerned about the drivetrain.
Thanks for your question. If you are trying to make more than 350 whp, then yes, the 6-Speed is the most reliable way we have found to hold the power. And you get the added benefit of a front torque-biasing diff, and the DCCD center diff.
We have done a video on that swap too if it helps.
th-cam.com/video/nUJ7E2Bh5g0/w-d-xo.html
th-cam.com/video/uf4tcG5GqDU/w-d-xo.html
Good luck with the swap, and Stay Tuned!
@@FlatironsTuning thanks for the links. Im getting all my parts list done. I want to be able to have what i need and no get lost when it comes time. Would you recommend the mooressport rear and front subframe, if i were to try to use the Sti axels
@@1atinlove You don't need those, but you could certainly install them. I'd say they are way overkill for anything but a purpose built track car.
Is this applicable to adm I have a blown ej205 it's impossible to find a ej207 unless your prepared to wait.Will my Forester gt heads bolt straight on to a ej25 block what else would need to be done
Thanks for your question. Yes, your Forester EJ205 heads will bolt right up. But I would recommend double checking that the cylinder head volume of your heads is close to, or the same as the USDM EJ205 heads. I suspect it is, but you would want to confirm that.
Hope that helps and Stay Tuned!
Okay, so either way buy the ej257 short block?
Thanks for your question. Yes, all of the hybrid options are designed around the STI piston, so that would be the best place to start.
Thanks for watching and Stay Tuned!
I understand that some pistons come with a higher dome. Would a piston with flat surface or a slight deeper dish work without having to buy hybrid pistons?
Thanks for your question. These pistons all have dished tops. The depth of the dish is what is used to control compression, so the hybrid piston has a deeper dish than the standard piston.
I hope that helps, and Stay Tuned!
Wouldn't it make sense to have the higher co mlm pression for someone who wants to run a higher compression n/a 2.5l? I want to go outside of the normal Subaru "turbo" and make a performance si gle cam ej25 in my 06 forester.
Sure, if you are wanting to build an N/A Subaru engine, you will definitely want more compression. I'd recommend you look into what the Open Light Rally guys are doing. They have to run a 2.5 liter N/A engine in that class, and they are getting them up to roughly the 2.0 liter EJ stock power level, which is pretty cool.
They are adding compression, tuning, and cams for the most part I believe.
If you can, take a look at Ecotech. They are having some good success with that formula.
Thanks for the comment and Stay Tuned!
Hello can you give a rough guideline for safe power for the 1.5mm head gasket, piston and chamber matching. Like how many kws or hp or psi is it safe to run at
Thanks for your question. If you are running the 1.5mm gasket, it is more ideal if you are running less than 20 psi of boost and shooting for less than about 375 whp. If you want to make more boost pressure or power than that, a stock thickness HG is better.
Hope that helps and Stay Tuned!
Hey flat irons, great videos. Do you have any info on ej20x swaps into say a 06 usdm lgt?
Thanks for your question. We haven't done that ourselves, but it seems to be more common. A lot of the components of the EJ20X are unique (like the turbo for instance), so the swaps seem to end up being much more complicated than it would seem at the beginning.
Getting the Dual AVCS to work would also be an issue, and if you just wanted single AVCS, you still have the problem where the pickup's on the cams are opposite of what the USDM computer is looking for. You may want to take a look at our JDM swap video as well:
th-cam.com/video/3ZwcQRsUI2M/w-d-xo.html
Hope that helps, and Stay Tuned!
Hey bro.. in nz the ej20x is mounted to every legacy gt 2.0 from about 03 to 08, 09 maybe but I could be wrong..
Anyway.. ive got that motor in both my legacy and S-GT (which is just a GH8 WRX), but there is a difference.. theres the ej20y, which comes in the manual variations, like of course the WRX.. that motor pumps out an xtra 20bhp more then the 20x but again thats only because of the transmission being an auto..
Key things to know, its a twinscroll turbo. Do your homework on them.. if its a "JDM" then try to gun for the jdm computer and all that aswell.. then u can retain the avcs, if you want.. and other things like its ability to be reflashed.. All in all, the motor is amazing.. infact id say one of subarus better ones..
Can we use both the forged piston and the kosworth gasket together? Would that make it more reliable??
Hi! This may sound like a dumb question but if I buy new head castings for a ej205 that has chamber matched to the ej257, can I run regular forged 2.5 pistons? Would that change the cpr? Or since I did the chamber match the cpr doesn’t change?
Thanks for your question. Yes, as long as you have the correct volume in the cylinder heads, you can run a stock thickness headgasket because your compression ratio will be correct.
That being said, if you are looking at getting new EJ205 castings chamber matched, you should also look at simply using EJ25 heads. That is also an option, and we have a video going into detail about that here:
th-cam.com/video/6Xzopgayw7c/w-d-xo.html
Thanks for watching and Stay Tuned!
How much power is too much for the thicker head gasket? Is 400whp too much? Thanks
Thanks for your question. I'd say that 400 whp, or say 20+ psi of boost is where the 1.5mm head gaskets are not ideal.
Hope that helps and thanks for watching!
Do you have a video explaining if the ej207 internals are compatible with the ej205 block?
Thanks for your question. I do not. The later EJ205's that we got here had the cross-drilled EJ207 crank, so there is no question that part crosses over. The bore is the same, so all of the 207 pistons would work, and I believe that the rods are interchangeable as well.
Really, the difference comes down to the case itself, which is open-deck on the 205, and semi-closed on the 207.
I hope that helps and Stay Tuned!
@@FlatironsTuning for sure thank you. Subbed
can you do a video on the avcs systems, im a mechanic coming up and im doing a new engine on a wrx, the one for the car is a single new one is a duel , thought about making my own system for the duel
Thanks for your question. We'll add it to the list of topics to cover :-)
Thanks for watching and Stay Tuned!
Got a question, not exactly a 2.0/2.5 hybrid but sort of along the same lines. I have a supercharged EJ253 and I am rebuilding a spare motor. I'm wondering if the heads are decked, can I get away with 1mm shorter rods (STI 130.5mm rods vs the stock NA rods 131.5mm rods ) rather than a thicker HG? Will I run into issues with quench and combustion? I guess it would depend on how much material is removed?
How would one go about doing a Type RA block with EJ255 heads?
Thanks for your question. You could certainly do that. The D25 heads have a smaller combustion volume, so you would get a slight bump in compression with that pairing.
If you run a 1.1mm thick headgasket, that would correct the compression to about 8.4:1.
I'd recommend going through our video on the B25 Vs. D25 heads if you haven't all ready:
th-cam.com/video/h6FdnJRWa6o/w-d-xo.html
Hope that helps and Stay Tuned!
So other than displacement. Is this a better way to make a lot power? Is it more reliable compared to making more power with just a 2.0 block and head?
Thanks for your question. The short answer is that yes, any power goal over about 300 whp will be easier with the extra displacement of the 2.5 liter engine, and that is the appeal. For instance, our 03 WRX project car with the 2.5 liter conversion is making a little over 300 whp on a 20G with a stock block and at only 18 psi of boost. To get a 2.0 to make 300 whp, you have to push much harder, and you will not have any where near the low-end torque of the 2.5.
Now that being said, of course there are people making lots of power on 2.0 engines too. Everything has to work together on the build, and you do have to push a pretty big turbo with a decent amount of boost, but it can be done. I wouldn't like to daily drive it though :-)
If you are trying to decide between the two, you have to look at your power goals, your budget, and how much of a powerband you want, and where you want the power to come on. Then compare a 2.0 build and 2.5 build and see which one checks the most boxes :-)
I just had my 06 OBXT block crack at 147k. I replaced the head gasket and used ARP bolts but I still got overheating and air in the heater core. Flushed heater core skimmed head cleaned up block still overheating. Vacuum tested the cooling system and it will not hold vacuum. I want to do a used 257 block but is there any advantages? Or will the 255 block be ok to use? New forged pistons/rods, etc. I am new to this platform so is there a recommendation of what size to bore to? TIA!
Thanks for your question. First, definitely take a look at our blog talking about the differences between the EJ255 and EJ257:
www.flatironstuning.com/blog/what-is-the-difference-between-an-ej255-and-an-ej257
Then look at our video that talks about the difference between D25 and B25 heads.
th-cam.com/video/h6FdnJRWa6o/w-d-xo.html
The short answer is that you should have B25 heads on your Outback, so the STI block is actually what you had to start off.
Hope that helps and good luck with the re-build!
@@FlatironsTuning Thanks I didn't know you ha a video on the heads too but I saw the one on the blocks and pretty much the internals are the only difference between the two. Thanks
@@saki10man No problem at all! And Glad that we could help!
My question is what’s the ideal hp that you could be running with the thickness heads gasket? No for a tracking car but could you some race one a time? I am planing on doing a hybrid swap
Thanks for your question. I would say that if you are planning on making more than 400 whp, or running more than 20 psi of boost, then the double thick head-gasket would not be an ideal way to go.
For what it is worth, they are just more prone to failure because they are twice as thick as stock.
I hope that helps and Stay Tuned!
So I bought an '02 that was OEM 2.0L turbo, and then the shop told me the prior owner had put in a 2.5L block. What's the best way for me to know which method he used? I'm assuming I could see a 1.5mm head gasket, but what if he machined the heads or put in different pistons or put the 2.5L heads on it? I'd like to know what I've got as a starting point. I have a cheap bore camera if I could put it down a spark plug hole.
Thanks for your question. That is a tricky question. Can you contact the previous owner at all? You can try to measure the thickness of the HG that you can see as a starting point, but it wouldn't be a 100% certainty.
Really, a lot of that information you could only find out by tearing the engine down. JE Hybrid pistons for instance pretty much look the same, they just have a deeper dish when you measure them.
I'd say that as long as the engine is healthy and running well, I wouldn't worry about it too much. Just run the car, and if you decide that you want to do a bigger build, it may be worthwhile to do an actual tear-down to see what you have.
Good luck, and let us know if you have any other questions!
Hi, I'm struggling to figure out what head gasket to use? I have an 08 ej255 block with sti t20 2.0 heads. A guy from cometic mentioned I need to use a gasket that suits the coolant passages? When CC'ing pistons and combustion chambers it is only going to be 8.5:1 So I'm thinking of just running a stock gasket.
Hey men, cheers from Panama (The country XD). I'm planning on doing a short block swap on my USDM wrx 2005. Do you think I'm going to be able to get some whp between 300 and 350? (Adding tune, turbo and other stuff, but keeping the internals of the shortblock stock)
Thanks for your question. If you are keeping with the 2.0 liter, it is going to be tough to get over 300 whp. The most common turbo on the 2.0 to hit that power level is something like a 20G, or maybe a Blouch Dom 1.5 XTR. The problem is they will be very peaky powerbands, and you may have to try to rev higher to give you more useable power. And on a stock shortblock, that can be problematic.
Now, if you do the hybrid swap with a 2.5 shortblock, you should be able to hit at least 300 whp with either of those turbo options and have a lot more useable power.
I hope that helps, and good luck with your build!
So, which option do you think is the best one to get those 300-350 whp I want to have (as reliable as possible as it is my daily day drive),
- Swap my current shortblock from WRX to STI's, and just follow your guidance on the video. Side note, I think if I choose this option I would go with the thicker head gasket, as I would rather prefer to keep the new STI shortblock unopened here in Panama.
- Or, Just buy new forged Pistons, forged Rods, Rings, and basically rebuilt the internals but keep the actual shortblock stock.
If your goal is to hit the 300 - 350 whp mark while stressing the engine as little as possible, then the 2.5 liter is your best bet. Simply put, you have to wind out a 2.0 more, or push a lot more boost to hit that same mark compared to a 2.5 liter engine.
I actually had basically the same goal that you mention , and that is why I ended up going with a full 2.5 liter longblock swap :-) My goal was to make 300 whp as reliably as possible to have a fun and reliable track car.
We did a video on that too if you haven't watched that yet :-)
th-cam.com/video/6Xzopgayw7c/w-d-xo.html
Is it possible to do the 2.0 block with the 2.5 heads if so what is needed?
Thanks for your question. That is not possible. With that combination, there wouldn't be a headgasket that would work, and it would also have a pretty bad combustion chamber design.
Hope that helps and Stay Tuned!
What about when you get the 2002 STI jdm 2.5 heads with no avcs?
Thanks for your question. If you have JDM STI heads, the approach for installing them to a 2.5 liter block is the same as we detailed here.
Hope that helps and Stay Tuned!
Can u still use my wrx trans flywheel and clutch. also can I use all my other parts off my wrx like the intake, exhaust all that?? Thank you
Thanks for your question. Yep, as long as you are using your WRX transmission, you can keep all of those parts.
Thanks for watching and Stay Tuned!
FlatironsTuning thank you so much
I try put 2.0 block wit 2.5 head what head gasket you recomend
Thanks for your question. Basically, you would want a 1.5mm thick head gasket if that is what you are going to use to correct the compression ratio. At this time, the best option would be the Roger Clark 1.5mm HG. Here is a link to those on our site:
www.flatironstuning.com/rcm-mls-single-head-gasket-1-5mm-04-06-ej25
Hope that helps, and Stay Tuned!
Thought you said it's not possible to use the 2.0 block with 2.5 heads?
so i bought a headgasket thats 1.0mm thick. Do you think that would be good enough?
I just picked up a ej257 block and am wanting to install my 253 heads. If i want to keep my current CR do i just use the 253 rods and pistons or does it really matter?
Thanks for your question. If you do want to keep your compression ratio, yes, you need to at a minimum use your pistons. The NA engines have a higher compression ratio, and that largely comes down to the the piston dome an cylinder head shape.
If you stay with a turbo piston, then your compression will most likely drop a good amount.
I hope that helps, and thanks for watching!
Awesome! Exactly what i needed to know. Thank you.
Do you have any idea what the total price would be for the first option of the hybrid build that you gave in the video?
Thanks for your question Carlos. We have actually put together 3 different levels of kits for the Hybrid swap. Here are links to those on the sight. It will give you a good idea what the cost of the swap would be:
www.flatironstuning.com/p-1896-basic-25l-hybrid-swap-install-kit.aspx
www.flatironstuning.com/p-1898-comprehensive-25l-hybrid-swap-install-kit.aspx
www.flatironstuning.com/p-1899-master-25l-hybrid-swap-install-kit.aspx
I hope that helps, and please let us know if you have any other questions!
So the one thing I still don't understand is why would you even want to do a hybrid swap? What does this even accomplish? Does it make it easier to make more power or something? But if your swapping in a 2.5 liter engine why even bother with the smaller engine heads...
Thanks for the question. Yes, you get a big bump in torque with the larger engine, and that extra displacement does make it a lot easier to achieve higher power goals.
As for why you would keep the EJ20 heads, the answer is generally that if they are in good shape, it reduces the cost of the engine swap by a good deal.
Thanks for watching and Stay Tuned!
@@FlatironsTuning Oh thanks for the info, I already have a EJ255 but it's the 05 version which is essentially a EJ257. What would you recommend to do if I want to get around 350 hp out of it
If you keep the 2.0 Heads and then do the STI short block, when it comes to getting TGV Deletes do you get the ones for the WRX or the STI?
Thanks for your question. Since you are just putting in an STI Block, your parts choice would be for the WRX. Specific to the TGV's, since you are moving the TGV's from the WRX over, you would just get TGV deletes for a WRX.
this can put in forester D25?
I have a question. Where might one acquire one of those fine shop shirts that you are wearing? hint hint I want to buy one.
Thanks Keith. Those are just Subaru Shirts that we have acquired through the years. I Don't believe that they are still making that one, but I'll check.
Would this mod work on a NA ej25? N off so what do you think the gain would be? Because 140/60 to the wheels suck lol
Thanks for your question. This would not really work on an NA EJ25. They start off with higher compression all ready, and there would be less gains from putting on a smaller cylinder head, and a lot more issues due to piston shape, etc.
If you want to make more power with the 2.5 Liter take a look at what the Open Light Rally guys are doing, and maybe reach out to EcoTec. They have developed some great engine packages for the Rally teams:
ecotechimportauto.com/
Hope that helps, and Stay Tuned!
Do I need to get both HG and JE Hybrid piston?
Thanks for your question. No, you would need one or the other. Since the JE pistons have a deeper dish, that corrects the compression ratio, so you can then run a standard thickness headgasket.
Thanks for watching and Stay Tuned!
What if it’s N/A application with an sohc 2.5 block and dohc 2.0 heads from an N/A
Thanks for your question Bob. We haven't worked with a naturally aspirated build at this point, so I can't offer much guidance. I have heard of putting on phase 1 2.5 DOHC heads on the NA blocks, etc., but I can't tell you much more than that.
You'd want to look at compression ratio, and how the heads mate up to the pistons that you are using as a start, and go from there.
I'd recommend talking to ASF Machine, as they have worked a bit with building 2.5 liter NA engines, and they would be a better resource than we are at this time.
Thanks for watching!
@@FlatironsTuning yall interested in seeing how it goes with ej251 sohc heads on the 257 block with the sti headgaskets I believe it will be a 9:1 motor and I will be pushing 5-10psi through it. I am currently looking for a 257 short block so I may have to grab the one you guys have. Would love to chit chat and figure some stuff out.
Hey Flatirons..great video. I know i'm a little late to the conversation but i'm looking to do the opposite. I'm interested in changing my forester 2.5l turbo ej25 engine for an ej20 2 litre (with alu manifold). I've heard it can be done with little modification ....btw...i know absolutely nothing about mechanics but just want my car to get running again and the ej25 engine is very hard to find. thanks
What if you want a high compression engine
The thing to consider with high compression would be maintaining an optimal combustion chamber shape. The simple hybrid swap will bump your compression if you use the stock thickness headgaskets, but there is a lot of overhang from the heads, and not ideal quench area between the piston and cylinderhead.
Ideally, you would want to either chamber match your 2.0 heads, and then run a higher compression 2.5 piston, or run a higher compression JE Hybrid piston, which is designed to match up to the 2.0 combustion chamber.
If you are going to run a detonation resistant fuel like E85, this is much less of an issue. If you are thinking of running pump gas, I'd say that you would want to stay pretty close to stock compression ratio.
Hope that helps, and good luck with your build!
Higher compression and you will crack the piston. Subaru engines aren't good for high compression as they low compression engines from factory vs say VW golf gti or r.
Any idea what displacement would be if you had a ej25 block/crank with Ej207 rods and head? standard combustion chamber. Does the rod length make much of a difference?
Thanks for your question. So putting a 2.0 liter crank in a 2.5 liter case has been done by a number of shops, and is considered a De-Stroker build.
It is a bit of a deep topic, but here are the cliff notes. Your displacement will drop to 2.3 liters, and if you use the standard STI rods, your compression will drop to about 7:1 aproximately. This is one of the origins of the +2mm rods. If you use the +2mm rods with standard STI pistons, it will bring the pistons back up to standard height, and then you have all of your standard compression ratios.
Manley does make a De-Stroker piston, so that you can use standard length rods and get the pistons to the correct height, but there are definitely some benefits from going with a longer rod.
If you search for a STI De-Stroker Build, or a 2.3 liter Build, or an STI Long Rod build, that should get you some more good information. Just don't get confused with putting a 2.5 liter crank in an older EJ22 case. That is another route to a 2.3 liter built but it is entirely different :-)
Hope that helps and feel free to call us if you have any more questions!
Thank you for the response! The +2mm rod = ej25 rod? I'm now onto my second build... first one didn't last as long as I hoped but was a lot of fun while it did! I did notice one the first build that there was excessive piston to deck clearance. I want to eliminate this for the next build.
Hello BigBear. Was this a de-stroker build? If you used a standard length rod, that would put the piston well below deck height, and lower your compression a lot.
The +2mm rod I mentioned is something that has to be custom made. There are a few companies out there that can produce them. We can get them from Pauter for instance.
Hope that helps, and good luck with the next build!
if I use the JE pistons the head gasket should be stock 2.5 or stock 2.0? thanks in advance
If you are doing a Hybrid build, you must run 2.5 liter head gaskets. If you are using the JE Hybrid Pistons, then the stock thickness head gaskets will be what you need. Good luck with your build!
@@FlatironsTuning hi
What are the specifications for the je pistons?
@@AntoineVirgo The JE Hybrid Pistons are designed to give you a compression ratio of 8.5:1 with the 2.0 head. If you want more detailed information about the pistons, here is a link to JE's site with all the info you could want:
www.jepistons.com/Catalogs/Sport-Compact/Subaru/ej257_ej20head.aspx
Thanks, and Stay Tuned!
what head gasket do you recomend for a 99.75mm bore?
Most head gaskets will work with larger bores. The only ones that don't from what we have seen are JE and Cometic, however, they do work on both 99.5mm and 99.75mm bores. You only need a different gasket if you go up to 100mm.
FlatironsTuning Hey guys, I see you do a lot with turbo engines. I know a lot of us over here on the N/A Subie side would love/really need a video on an N/A hybrid or frankenmotor, as they're known. 2.2 heads on a 2.5 block, 11.0-11.5:1 compression (I don't know the exact number), cams, porting and polishing-everything to make an angry N/A. There's a need for a pretty much all around video explaining everything we need to build it, what to do, what not to do, etc. There are a few build threads scattered about the various forums, but a lot are vague and/or not very detailed. It would help to clear up the confusion, and I know I could certainly use it as that is my current goal for my '99 BG5 5MT wagon.
Thanks for the suggestion! We don't do much with that, but it is something that we will keep on our list. I'll tell you that one of the guys we sponsor is Racer Dave - Dave Brown. His car is an Open light rally car, so a 2.5 liter N/A engine. Some of those guys are starting to figure out some things on making N/A power, and I know that Dave has some things in store. I'd be worth checking out his channel as well :-)
FlatironsTuning thanks for the point in the right direction! I'll check it out.
just put ej 25 heads on - avoid all this rubbish ! = not even that big a differance - except $$$$$$$$$$$$
Don't do it 2.0l blocks are way more reliable!