This is a discussion on Knock Knock- my hybrid motor build within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; Originally Posted by 20WRX04 I wouldn't want to put EJ20 heads on an EJ25. I've read about quite a few ...
I would leave everything alone and just put the stock STi block with stock STi internals in there and not fuss about with porting stuff or doing forged internals. Built motors never, ever, ever last as long as they are advertised to and they almost always eat more oil than the owners are comfortable with. I may get a few heated responses to saying this, but you're better off trying to keep it simple when it comes to motor replacement. Which is not to say that there aren't some really sick things you could do if you're tearing your car apart...you could. Take it from someone who did 2 built motors in his last WRX...not worth the aggravation. Get a reliable setup that runs properly and has close to factory longevity/lifespan.
Also, for what it's worth, if you use stock size headgaskets on 2.5 block with 2.0 heads, your compression is just under 9:1; the reason people complain about this is because they have a hard time running the boost numbers they want to run, i.e. 25psi on an 20g or a Green on race gas. High compression is a totally different game. I would recommend you talk to a motor builder like axis or crawford and ask them how they would address this. The long answer is "low compression aftermarket pistons." The short answer is "thicker headgasket."
I might also try to find a JDM STi 2.0 block if I were you...rock solid internals, super smooth powerband, no retune/turbo upgrade required to make everything run smoothly. I have often thought of replacing the the stock USDM 2.5L motor in my STi with a JDM 2.0L motor...assuming I had a big pile of cash lying around
Best of luck.
^^^ Thanks for the input & advice Tim. I really appreciate it. This is my first Subaru motor build & i'm just scratching the surface of what I should & shouldn't do. My buddy, a Subaru master tech, will be doing most of the work so at least I know that portion will be taken care of. There's a lot of things to think about when it comes to these kinds of situations. I'm just going to take it all in & see where it leads me.
So you're saying it's a good thing to use a thicker head gasket with 2.0 heads on a 2.5 block? I've got so much to learn when it comes to hybrid builds.
I would look into a JDM 2.0 block, however i would be getting the 2.5 motor for $400. Can't beat that!
As of right now i'm leaning toward a build with my 2.0 motor but i'm not ruling anything out yet. Decisions, decisions.
OT but how do you like VaBeach/Norfolk? I lived out there in 2004. Good times.
Last edited by 20WRX04; 08-01-2008 at 08:43 PM.
The thicker heaadgasket will basically, in very plain speak, add more volume to the combustion chamber so that the compression ratio is lower. This is a VERY overly simplistic explanation, but it's what a lot of other tuning communities do when they want a little less static CR without cracking into the motor to do pistons.
VA is nice, reminds me of a cross between southern california and Long Island, where I grew up. I am still having a hard time coming to grips with how much more expensive everything is compared to Pensacola, though....it's crazy!
I loved VA. Yeah it can be expensive down there. The state taxes are lower but they hit you with all kinds of other taxes to make up for it. And you gotta love the torrential downpour season.
Ok, so i've decided to keep it extremely simple. Depending on the condition of the internal engine components, I might be able to just get away with getting ARP head bolts, Cometic head gaskets, Cosworth bearings & hi flow oil pump. And i'll get the valve seats refinished. If I have to replace anything else (crank, rods & pistons), i'll probably just go stock but i'm not ruling out better stuff. There's too many possible cons, let alone additional mods, to running a hybrid motor. I'll hopefully be pulling the motor out at the end of August. Happy bday to me,.. I think.
I think that's best - this is going to be expensive enough. Again, let me know when all this is going down, and I'll try to come out for a day or twoOriginally Posted by 20WRX04
Thanks TR, i'll keep all that in mind. I think i'll just end up getting a stock crank for my motor. I have a VF39 set up & I really don't want to put another motor in there that already has miles on the bearings, etc. It would only be a matter of time before the used bearings go.
Ok, a little update on my motor swap. If all goes well, I should be pulling the motor in a few weeks in favor of an STi motor. I decided to go with that motor & put my WRX heads/cams on it. Hybrid ftw! I'm going to replace the bearings in the STi motor with Cosworth bearings. I also just ordered P/P/C manifolds, TGV deletes, phenolic spacers & a new UP from Grimmspeed. I also got a larger TMIC that will be coated with a thermal dispersant from SwainTech. They are local to me, so it's a no brainer. Also got Autometer EGT & WBO2 sensors & gauges, along with an Innovate LC-1. One step colder plugs are on the way too. There's so much more I have yet to get....
Might i ak how did u blow it?