Xise Posted June 8, 2008 Share Posted June 8, 2008 Hi, this is my first post. I have been trying to find out how interchangeable subaru parts are. I know that my 2.5 RS has the EJ25 block as does the STi, i wanted to know if mine was a toned down version or the exact same block. Basically what I am trying to do is convert my SOHC heads to the DOHC heads/ cams that the STi uses, I just want to know if all the valves and stuff would line up....I looked at the head gaskets for both cars and they look identical. I am basically asking if STi parts would bolt directly on to my RS motor. Can anyone help me out??? Link to comment Share on other sites More sharing options...
zukiru Posted June 8, 2008 Share Posted June 8, 2008 people put sti/wrx heads on those blocks. your answers have been covered many times over at the more impreza oriented sites. not that this isn't a good place to ask or talk about this. but you will get more answers and experience at I-club, Nasioc or RS25. Link to comment Share on other sites More sharing options...
Xise Posted June 9, 2008 Author Share Posted June 9, 2008 I tried posting at all except one of those boards and you are the first person that gave an actual answer. Thanks a lot man you helped me out a ton, now it is time to empty my savings account lol Link to comment Share on other sites More sharing options...
Xise Posted June 9, 2008 Author Share Posted June 9, 2008 Link to comment Share on other sites More sharing options...
Zefy Posted June 9, 2008 Share Posted June 9, 2008 do not just jump into this. your engine has pretty much only one thing in common with an sti engine... the part that says 2.5... besides the displacement the blocks are completely different. sti block is designed for boost with low compression while yours is designed for N/A furry with high compression. if you slap a turbo on your car and expect to run stock sti boost you will granade your motor. do a search on nasioc or something as this topic has been discussed MANY MANY times. there is even a section in there exactly for doing such mods. http://forums.nasioc.com/forums/forumdisplay.php?f=50 its a BIG job... Link to comment Share on other sites More sharing options...
boxerbob Posted June 11, 2008 Share Posted June 11, 2008 people put sti/wrx heads on those blocks. your answers have been covered many times over at the more impreza oriented sites. not that this isn't a good place to ask or talk about this. but you will get more answers and experience at I-club, Nasioc or RS25. Clubwrx.net , wrxtuners.com . i probably know more sites but they are small. Link to comment Share on other sites More sharing options...
SubPar Posted June 11, 2008 Share Posted June 11, 2008 Normally Aspirated with bolt-on Forced Induction Powertrain http://forums.nasioc.com/forums/forumdisplay.php?f=50 Built Motor Discussion http://forums.nasioc.com/forums/forumdisplay.php?f=144 Link to comment Share on other sites More sharing options...
Xise Posted June 15, 2008 Author Share Posted June 15, 2008 Thanks a bunch guys, ya i figured the RS had a slightly different block than the STi did, I can't thank you guys enough for your help...the first forum to actually give me a quick answer instead of simply dismissing me as a noob. fact is this is my first subaru and my first AWD, I am use to BMW motors so this is all new to me. And as far as the turbo is concerned i can't even afford to think about doing that now....I just want to get some new heads/cams/gears for the first actual mod....maybe if I am feeling fiesty...(and have the $$) I can get my block machined...or just buy a Sti long block and THEN get a turbo.....I will determine that after I see how fast some DOHC heads are on this car. Actually here is a good question how much HP do you think an RS motor could produce if I did stick w/ NA? AND! does anyone make performance differentials for under 1 grand...for just one...I mean damn. Oh ya almost forgot so oficially what motor code is mine? EJ2555, EJ255T, or EJ2557?? Link to comment Share on other sites More sharing options...
PoorManzImpreza Posted June 15, 2008 Share Posted June 15, 2008 what year is your rs? I assume since your wanting DOHC that it is not a 96-98 car since they had the EJ25D which was already equiped with factory DOHC, so assuming it is a new gen phase 2 N/A 2.5 SOHC motor it is likely to be an EJ251 motor. Having said that there have been figures floating around on NASIOC stating that these SOHC 251 heads flow VERY well, more than some OE DOHC heads. What I would advise is to do some major ready (on NASIOC http://www.nasioc.com/ and RS25 http://www.rs25.com/ ) and questioning (maybe not so much on NASIOC ). Plan your setup, think about what you want from your car. BMW tuning is mostly N/A tuning while subaru tuning is mostly turbo tuning. One last thing, changing the final drive in an AWD subaru require changing the front AND rear diff ratios. The rear diff is a tiny bit easier than your average BMW, the front diff requires removing and splitting the tranny which is very involved... depending on your year of RS you might also already have 4.111 gears..and considering that suby final drive ratios go like this: 3.545, 3.7, 3.9, 4.11 and 4.44 that ain't bad. Feel free to ask any questions we are a friendly board and love to assist our fellow man (and woman) to become as equally addicted to subarus as we are;) HTH, Kaz Link to comment Share on other sites More sharing options...
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