I can't seem to find any info on this anywhere, but what exactly is the difference between the various blocks on the subbies? I mean you have the RX 2.5 block, the sti 2.5 block, the wrx 06 2.5 block, the 2.0 wrx, the 2.2 legacy, 2.5 legacy. Are the short blocks all interchangable with the heads and intakes or are some interchangeable and others not? For instance could you take a 2.2 legacy block and throw wrx heads and such on it? Same question for the RS 2.5 block or are there structural differences too?
I know that all of the Turbo 2.5L blocks are the same. I know that all of the NA 2.5L blocks are the same. As far as I know all of the EJ motors can swap heads around. The 2L WRX motor is the only one like it in the US. The EJ22 is the strongest block with its closed deck design. The EJ257(the 2.5L turbo) is a semi closed and the 2L is an open deck design. I can't explain those diffences though but I am sure someone here can.
EJ20 in the 02-05 and theres a difference in the 2.5 blocks as far as internals when it comes to the wrx and Sti..or there better be cause if there isnt i was lied to and im pissed
Well from my understanding, the 06 WRX and the 06 STi are very similar. The WRX has different heads and pistons(rods and crank the same both forged). The difference is not in the materials but it was to change the compression ratio. The STi is 8.2:1 and the WRX is 8.4:1.
so i guess boost u could run safely on an 06 WRX would be lower than what u can run on an STi? i guess the higher compression would be nice at an autoX with good off boost response
I would assume so. You would have slightly faster spool on the the WRX and slightly more torque at a lower RPM.
Cool stuff. I hope to get a 2.5 block eventually for my lil bugeye, just curious if the 2.5 rs block could be used since I plan on changing out the internals anyway.
You do not want to run a 2.5rs block even if you are changing out the internals. It will not hold boost very well especially if you are planning on making big power.
Ok, maybe this sounds silly, but since the wrx ej207 block is open and is able to hold boost ok, why would the 2.5 rs block be worse than the 2.0 if both are open? Sorry, I could tell you anything you wanted to know about the chevrolet small block but this is all new stuff to me!
the cyclinder walls are slightly thinner on the 2.5 block in order to get the higher displacement in the same dimension block. This adds to the tendency of cylinder walk.
The 2.2 block is the ish. My next setup will either be 2.2 Block, 2.5 Crank, 2.5 rods, Mahle conversion pistons 2.35 liters or 2.2 block, golden eagle sleeves, stroker crank etc... 2.7-2.8 liters
the WRX uses a ej205, the ej207 is the jdm sti motor and i believe that is semi-closed deck. that means its a lot different than the wrx motor.
Richt. I can't remember if the EJ207 is semi closed for fully closed, but it is alot stronger than the EJ205. If you want the strongest block Subaru makes get the EJ22 from a Legacy turbo from the early 90's. If you want the next xtrongest then the STi/WRX/Forester XT/Leagacy GT/Outback XT motor would be the best choice. The NA 2.5L is a open deck design. I know. It gets confusing
The coolant passages dont line up exactly on all of the EJ series blocks, but its nothing that a dremel tool cant fix in just a few minutes. Matt
Ok, last question on this lil thread....if the forester 2.5 and legacy 2.2 are decent blocks to use and are every bit as good as the sti block, why do they sell for significantly less cash? I saw a guy selling a forester 2.5 xt short block for $650 and took a while for him to sell it. If this is the same block that people are shelling out $1500+ for...just doesn't make sense. Is there something else different about them?
Not that I know of. All of the turbo 2.5L motors ause the same block. I guess its cause it has STi in the description.
Fair enough...I figured it was something like that. I did finally find some pictures of the various open and closed deck blocks on i-club site.
also, the pistons in the 2.2 are crap, the rods are a little better but i would suggest replacing both is max HP is your goal. was that forester block new, i dont know who in their right mind would buy a used STi block for 1500 dollars, what a rip.
Nah it was not new, it was from a wrecked forester with 16k miles that was hit in the rear. I guess I should try to find a decent short block when the time comes. Anyone have any suggestions for places that have reasonably priced short blocks?
If you're looking for a cheap setup try to get N/A SOHC heads from a 2.5RS to go with that STI/Forrester/Legacy block. They flow better and with engine management they shouldn't be a problem.
Yep I'm looking to do the same when I turbo my RS. Oh and if someone decides on this setup please make sure you change out the cams. Power dies uptop.
Any idea where has reasonably priced blocks other than just waitin to jump on one on the foums? As for a cheap setup, the cams I have seen are not very cheap at all! Ya get a 2.5 rs heads and then put cams in them and you are looking at proly $1000+ for cams from what I have seen unless the cams differ from the wrx cams. What is the difference between the wrx heads and the 2.5 rs heads?
2.5 heads flow better. From what I hear wrx heads are quite restrictive in comparison. Cams are like $150 from delta to have them reground. And I'm sure you can find heads at a junkyard. Won't be $1000.
But are the sti and wrx heads dohc's? I would think that the dual overhead cam would flow better than a sohc...any chance of having my wrx heads ported and such to make them flow closer to the sti heads?
The biggest problem with wrx heads is the cams. A nice port job on a set of wrx heads should get you plenty of flow. Matt
ok from what i understand from reading this if i want to build i really high hp STI i should just take the STI block out and put a legacy EJ22 engine in it? does the engine mount up to the tranny with no problems?
All of the Subaru tranny's are interchangable. Atleast back into the 80's. If building a big HP motor I would stay with the larger 2.5L and just put forged internals. Even with stock heads and exhaust manifolds this setup can make 600+ at the wheels. How much more would you want?
i dont think it would be cost effective to do that unless you are builing a bored and stroked 2.2 for racing etc, like slowwrx was talking about.
Just think of blocks in three terms, open deck, semi open deck, and closed deck. Semi Open deck has been prove reliable up to about 600-700hp range. The ideal high horsepower block is a 2.2 sleeved by golden eagle to what ever size you want. You can sleeve a 2.2 to 2.0 or 2.8 and you might even be able to get more displacement out of it but I'm not really sure. If I was building an all out Time attack car I would probably build a 2.4 you spin them up really high, the pistons aren't to big and the rod ratio is good so you don't put massive side loads on the pistons. Matt
I think in terms of what Crashtke is looking at SOHC rs heads with a stock sti shortblock might be the best answer with forged internals. It's a nice median between huge power and breaking the bank. Porting the wrx heads could work but I think that'd cost more than spare heads from a junk yard. It doesn't sound like he's trying to go crazy with breaking his bank account.
http://www.rs25.com/forums/showthread.php?t=48323&highlight=wrx+heads This thread shows a pic of all the different heads so you can make your own opinion
Did any of you look at the above link? They have the ability to sleave an ej20 or EJ25 and effectively make it a closed deck block. With this I was thinking an EJ25 rs block sleaved could be a really strong block. I guess that you would have to then get all the forged internals too though :/ Yeah I am not looking to break the bank, but I have been looking lately at the various turbo options and realized that if I am going to get a good turbo I might as well have a stronger block to mate it to. I mean I could get a TD05-18g now and then when I swap blocks it would be fairly small for a 2.5 block. So, why not do the block swap first then worry about the turbo after that is up and running. Just building up the transmission is a bank breaker...PPG is REAL proud of their gears. A 1-4 set for our 5 spd is around $4500 just for the gears. With the sti 6 speed you are looking at that much or more for a weaker transmission. I guess my goals are not to have 6000 hp to the wheels, but I would like a vehicle with a reliable 450-500 hp that can put it to the gound without having to worry too much about a transmission detonating (already been there and done that...broke the casing on a th-350 chevy tranny). Luckily I have a guy who is a good friend of mine that will do porting for free! Viewing the above link it looks like the wrx heads just need a bit more meat taken out of them. Prior to doing the swap I think I will probably try to find a spare set of wrx heads to get worked on and rebuilt as this is my daily driver I am planning on working on. If I can recruit enough help I might try this myself....undecided. My buddy Andy, mentioned above, is a guru when it comes to cars of all sorts. He had a 8.98 second 1//4 mile mustang on a stock block! Well that is until he broke the block in half striaght down the middle, lol. He is opening up his own race shop and is actually getting an aw dyno. I am just at this stage trying to plan this out ahead of time, see what options there are for various combos. At this point I am leaning towards a sti SB with some forged pistons thrown in for good measure. I am guessing that should get me into the 400-450 range fairly safely. Then I have to worry about the tranny....4500 here, 4500 there, lol.
Having a friend that will do the porting for free is a huge help. I just figured that getting a professional job done to your wrx heads would cost more than getting the sohc rs heads.
Yeah he is also a tranny genius. He has worked on everything from cobra mustangs to evo's. He can even build up automatics to withstand some serious pressure. He is a great guy, just stays super busy with work.