Question for Phyrram

[Samiam1017]

In another thread(don't remember which one). You mentioned that the ecu,harness,throttle body should stay together. I have a 05 ej20. I ordered a 08 ej25 short block. What should be done to the heads before they can be used on the new block, Whats the advantage /disadvantage to this hybrid build. I'm assuming that moving over the other parts this will work with a proper tune. What else should be done for a strong street motor. What about headers? Or other parts when I'm looking what "year" is the motor or isn't that really relevant

[PhyrraM]

If your only planning on using the shortblock, then electrically you treat it like the '05 - using all your '05 components.

There is some discussion as to how to properly address the slight bore mismatch between your 2.0 heads and the 2.5 liter block. You CAN bolt everything together as-is using 2.5 liter headgasket and it WILL work with a proper tune. The issue is that there are some complaints of "hot spots" making tuning ignition timing hard. A safe tune should be not problem. The ideal way is you have somebody (search NASIOC) CNC the combustion chamber of the heads to match a 2.5 liter head, then you tune it like a 2.5 (just on a 2.0 ECU). You can also use actual 2.5 liter heads with a relocated cam sensor.

I reccomend a "matched" set simply so you know everything will work. There ARE many permutations and swaps that will physically work, but each will have it peculularities that making a blanket reccomendation here on a forum makes little sense as it's easy to miss a detail and end up with something that doesn't work and a lot of "forum finger pointing".

[Samiam1017]

I do remember seeing a write up about a company in CA that CNC matched them. I'll have to go back and look again. But as with any topic ever discussed on any forum there was guys that loved it and the guys that hated the idea for what ever reason. I figured it never hurts to ask. Is there anything that is not "bolt on" that is highly recommended. Thx again

[PhyrraM]

I do remember seeing a write up about a company in CA that CNC matched them. I'll have to go back and look again. But as with any topic ever discussed on any forum there was guys that loved it and the guys that hated the idea for what ever reason. I figured it never hurts to ask. Is there anything that is not "bolt on" that is highly recommended. Thx again

The way I see it is that doing the CNC matching work can not hurt anything. All your doing is replicating what Subaru did on factory motors which get $$$ more in R&D than any aftermarket company can do.

As far as not doing the CNC work? Well, there are tons of folks who have built 2.5 liter hybrids with out issues. IMHO, as long as you build a safety buffer into your tune, I cannot see a problem.

Disclaimer...I am a street based driver who sees no need to persue more than 400ish HP in a WRX, much less an 818.

[JRach]

I do remember seeing a write up about a company in CA that CNC matched them. I'll have to go back and look again. But as with any topic ever discussed on any forum there was guys that loved it and the guys that hated the idea for what ever reason. I figured it never hurts to ask. Is there anything that is not "bolt on" that is highly recommended. Thx again

There's also a shop in Colorado I've personally used. Same work, but half the price.

[Samiam1017]

Details. What other mods did you do to your build.

[Evan78]

I asked Clark Turner about this setup and posted his email response in another thread (http://thefactoryfiveforum.com/showthread.php?2472-SubuGurus-engine-assembly-options&p=25513&viewfull=1#post25513).

[Samiam1017]

I asked Clark Turner about this setup and posted his email response in another thread (http://thefactoryfiveforum.com/showthread.php?2472-SubuGurus-engine-assembly-options&p=25513&viewfull=1#post25513).

Well apparently Clark turner does like the idea at all. I've been searching around for more info. But I haven't heard any real reason why do this? Except that you need a new short block and you already have the heads. I guess I have some real thinking to do now.

[Evan78]

It's not a bad combination, just check into the head work. The displacement is partly just a preference, some people love a high reving motor, which the 2.0 is better for, but if you just want to make power, the 2.5 will do it a lot easier.

[Samiam1017]

Ok after some research I guess I have two options. Forged pistons or cnc the heads. The ej20 heads refreshed with a cnc job is around 1100. But I still have the weak link. The stock pistons... So if I just freshen up the heads (no cnc) and go with the forged pistons that would probably be better ? What do you pros recommend. Thx

[longislandwrx]

what's your power goal?

with a proper tune 2.5L STI block should be good for 400WHP no problemo, It's been known to handle more but in terms of reliability/longevity I hear 400 is the magic number.
The machine work may be overkill depending on your horsepower goals. Hundreds of people have done hybrids without it with great results.

A 2.5L master hybrid install kit with a thicker headgasket will be fine for moderate hp goals.


also, although i'm not an expert like Clark... saying "It needs pistons at a minimum no matter what the end combination." is just an outlandish statement.

[Samiam1017]

I never really set a hp goal. Being unfamiliar with these motors,the terms used to talk about them, whats compatible with what and what each "stage" means I thought it best to just look at the best way to have a fresh engine. Without knowing how the car was taken care of and that it was a salvage vehicle, I was looking to be more safe then sorry. I couldn't find a reasonable rebuild cost so factory short block seemed the way to go. But after reading some of the write ups reliability became a concern with this hybrid set. Do you have any good links. Who makes the master hybrid install kit. Who do you use as I'm only about 2 hrs from NYC and Philly theres got to reputable and inexpensive engine shops around. Thx

[Evan78]

Ok after some research I guess I have two options. Forged pistons or cnc the heads. The ej20 heads refreshed with a cnc job is around 1100. But I still have the weak link. The stock pistons... So if I just freshen up the heads (no cnc) and go with the forged pistons that would probably be better ? What do you pros recommend. ThxIs that price from EQ Tuning? What is the cost for machining alone? I'm not advocating machining or not machining, just curious about the details.

The common failure for the 2.5L motors is cracked ringlands, that is probably why Clark is saying to drop in forged pistons if you've got it out and apart already. Don't make a decision based on my opinion, but my uneducated guess is that it would be better to machine the heads than replace the pistons if you have to choose between those two options. If I were in your shoes, I'd probably elect to wait a while longer to raise additional funds to build the motor the way you want.

[Samiam1017]

Is that price from EQ Tuning? What is the cost for machining alone? I'm not advocating machining or not machining, just curious about the details.

Ya it's from eq tuning. 500 valve job. 200 surfacing. 450 cnc. There the only company that bothered to return a call or email??
I'm not sure if ajw performance can do this. I haven't called or emailed them,but they never chimed in with advice. And I believe there the only shop that is active here.

The common failure for the 2.5L motors is cracked ringlands, that is probably why Clark is saying to drop in forged pistons if you've got it out and apart already. Don't make a decision based on my opinion, but my uneducated guess is that it would be better to machine the heads than replace the pistons if you have to choose between those two options. If I were in your shoes, I'd probably elect to wait a while longer to raise additional funds to build the motor the way you want.

That's why my thoughts went to the forged piston. But I've been getting mixed reviews about putting them in without splitting the block. Most recommend honeing. So I guess I need to find a shop that can do that properly. The engine shop I used in past builds (all chevy v8s) and is currently doing a big block 396 for me has only done 1 valve job on Subaru heads. I don't think they can do it without buying more tooling.

[longislandwrx]

a built shortblock from Rallispec.... one of the best loved in the scene right now.

http://www.rallispec.com/prod_block.htm

$3500 and good for up to 600hp you'll never stress again

figure appx $1000 for a master kit and $500? for assembly.


you can also go the stock shortblock and save $1500, but questionable reliability as the power goes up... are pistons essential at any level like clark said... i dont think so, but if it helps you sleep at night.

as for assembly. Rallispec does it but i dont know how much they charge, personally I've used http://www.performanceautosolutions.com/ Dave Brown is a top notch tuner as well.

as for machine work, on LI LAB MACHINE in lindenhurst is a cut above... see what i did there?

[longislandwrx]

oops, just saw that you bought the block already... skip the rallispec part.


Personally if it was my build, and i'd already bought the block. I'd have PAS do a set of drop ins, assemble the block with the 1.5mm cosworth gaskets and be a happy camper.

[metalmaker12]

As power goes up, how much power do you want in such a light car, 300-400 is plenty good for me

[Samiam1017]

oops, just saw that you bought the block already... skip the rallispec part.


Personally if it was my build, and i'd already bought the block. I'd have PAS do a set of drop ins, assemble the block with the 1.5mm cosworth gaskets and be a happy camper.

I'll have to call them. I emailed but no reply. Everything I've read the block still needs to be at leasted honed. They make a lower compression piston for a hybrid set up.
Thx

[longislandwrx]

I'll have to call them. I emailed but no reply. Everything I've read the block still needs to be at leasted honed. They make a lower compression piston for a hybrid set up.
Thx

Correct me if i'm wrong but if you have a no mile shortblock the motor should have a factory hone? Unless they hone it again to loosen up the motor a hair? Not really sure, I never asked.

[Samiam1017]

Correct me if i'm wrong but if you have a no mile shortblock the motor should have a factory hone? Unless they hone it again to loosen up the motor a hair? Not really sure, I never asked.

It's the same thing I thought. If there the same size as factory and it's a brand new short block. Why does it need a hone. But on the Subaru forums that's what they say to do... I talked to my local engine builder. He didn't see a reason to if they were factory size. He did say if I buy them to bring them and the block down and he would check all the specs to lmk what he would do...I may see if my local distributor has them and if so get them and check it out cuz I could always return them

[PhyrraM]

A few reasons why drop-in pistons are not reccomended:

The factory pistons use a hyperutectic cast aluminum and run at very tight piston to wall clearances compared to aftermarket forged pistons. This is because forged pistons have a much greater rate of expansion as the pistons heat up. So, a proper drop-in pison needs to be a precise amount smaller than the OEM piston.

The factory cast pistons are designed to the way that the factory hones the block on it's mass production machinery. This honing process is not exactly the same as how an engine builder would hone your block. This mass production based process may not be 100% perfectly round, but it IS very repeatable...so the pistons can be designed and produced to accomodate these "imperfections" without negative effects. In fact, there can be such a variance in factory honed bores that Subaru makes at least two different pistons. Once the finished bore is measured, the case is stamped A or B (possibly C) based on the final dimensions of that bore. Four bore means four distinct stamps. You can look at every Subaru case half and see the 2 stamps from the factory. Further down the assembly line either an A or a B piston is installed in the proper bore. A single motor can have any combination of piston sizes from the factory. (FYI, they 5 main bearing sizes are also stamped for bearing selection during crank installation.)

Aftermarket pistons are designed for perfect bores of the "published" size. Ask yourself, how can a single piston fit both A and B bores? While many have had luck with drop-in pistons, many others have just proven them out to be a false economy. YMMV.

Also, keep in mind that EVERY truely professional performance engine builder - of any type of motor - Doesn't even touch the bores until the pistons are in hand and measured. Exactly the opposite of a drop-in piston.

[JRach]

A few notes on machine shop costs and such...

Proper assembly is very time consuming. Like anything else you get what you pay for. Double and triple checking clearances, proper ring gap etc etc etc which all depend on the application (street, occasional track, drag, fuel, etc).

I just started an engine build for a customer of mine, here's a break down of the costs to get a general idea of what to expect... he's a friend so a bunch of the prices are discounted a bit.

99.75mm Pistons- $596
Stock rods- free
New oem 79mm crank- $345
ACL Race/Rod bearings- $147
OEM 11mm oil pump- $162
OEM Gasket set- $286
ARP head studs- $196

So JUST for the parts of the shortblock (minus the gasket set and head studs, keep in mind we're re-using the stock rods)
Total- $1,250

In addition we're re-using his existing case halves (after cleaning and re-machine work of course)

Proper Machine work costs-
Bone/Hone using torque plates- $435
Deck block halves- $145
Cleaning fees- $85

Total- $665

We're already at $1,915 and havn't even added in labor time yet (shops range anywhere from $90-$160/hr).


A few reasons why drop-in pistons are not reccomended:

The factory pistons use a hyperutectic cast aluminum and run at very tight piston to wall clearances compared to aftermarket forged pistons. This is because forged pistons have a much greater rate of expansion as the pistons heat up. So, a proper drop-in pison needs to be a precise amount smaller than the OEM piston.

The factory cast pistons are designed to the way that the factory hones the block on it's mass production machinery. This honing process is not exactly the same as how an engine builder would hone your block. This mass production based process may not be 100% perfectly round, but it IS very repeatable...so the pistons can be designed and produced to accomodate these "imperfections" without negative effects. In fact, there can be such a variance in factory honed bores that Subaru makes at least two different pistons. Once the finished bore is measured, the case is stamped A or B (possibly C) based on the final dimensions of that bore. Four bore means four distinct stamps. You can look at every Subaru case half and see the 2 stamps from the factory. Further down the assembly line either an A or a B piston is installed in the proper bore. A single motor can have any combination of piston sizes from the factory. (FYI, they 5 main bearing sizes are also stamped for bearing selection during crank installation.)

Aftermarket pistons are designed for perfect bores of the "published" size. Ask yourself, how can a single piston fit both A and B bores? While many have had luck with drop-in pistons, many others have just proven them out to be a false economy. YMMV.

Also, keep in mind that EVERY truely professional performance engine builder - of any type of motor - Doesn't even touch the bores until the pistons are in hand and measured. Exactly the opposite of a drop-in piston.

Great info here, I can't tell you how many customers i've tried to talk out of using drop in pistons to save a couple bucks!

[Samiam1017]

phyrraM thx for that explanation I've seen that similair post a bunch of times but didnt understand what they were talking about, but there's something about the way you explained it that I see now. And I looked at my motor and it's stamped on the pistons very easy to see..

jRach What's your Thoughts/experience with hybrids? I really can't do both forged pistons and cnc heads. I would be onto a long block for almost 5 grand at that point..it's either one or the other( I could always do the other down the road) or just get the proper sti heads. If I didn't have another project going I wouldn't care as much. Thx

[NonProfit]

...there's something about the way you explained it that I see now. And I looked at my motor and it's stamped on the pistons very easy to see.

Yes, PhyrraM is schooling us all in the ways of the Subaru.

[longislandwrx]

Good info PhyrraM.... I suspected as much but good to have it all laid out. I've had good luck with 2 engines both with drop ins. Although I'm sure the builder mic'd them up though and they were within acceptable limits.

[JRach]

IMO if you've already dropped the money on a EJ257 shortblock you're better off having the combustion chambers matched! If you're set on forged pistons, what's another $200 on having the machine work done on the heads?
Contact ASF machine in Colorado. They do it for $179 (if you pay them do a valve job as well), not sure what they charge without.






jRach What's your Thoughts/experience with hybrids? I really can't do both forged pistons and cnc heads. I would be onto a long block for almost 5 grand at that point..it's either one or the other( I could always do the other down the road) or just get the proper sti heads. If I didn't have another project going I wouldn't care as much. Thx

[longislandwrx]

They will cnc the heads and a valve job for $180??

[PhyrraM]

They will cnc the heads and a valve job for $180??

I read that as:

If your already paying them to do a valve job, they will add the CNC work for $179 more.

[Samiam1017]

I read that as:

If your already paying them to do a valve job, they will add the CNC work for $179 more.

I emailed them for info and pricing so if I should get a reply I'll pass the info on

[longislandwrx]

makes sense and post was edited. ty

[flatfourspec]

I have done quite a few hybrid builds. I will not do one without CC matching the heads to the block. I have been using Larrys Power to do them, I think it is around $350 a set plus shipping. The thing I don't like about doing them without opening up the combustion chambers is the compression difference: stock EJ257 is 8.2:1 vs close to 8.8:1 you would be making without opening them up....let alone the hot spots and tendency for detonation. I don't like the idea of just tossing a thicker head gasket in place to compensate for it when throwing gobs of boost at it. And if you plan on throwing more boost at it definitely put pistons in it right away as earlier stated. Ringlands are an issue even with stock boost levels and normally crap out before 120k. When going a new block I haven't had an issue dropping in pistons on the factory hone, no hone is as good as a factory hone. And also, choose wisely for pistons. A lot of people cheap out with CP's, remember this is where your power is made. A coated skirt, offset wrist pin and polished face are a must in my book. I personally use Cosworth's. The stock heads will flow plenty for max power levels that a car of this weight will take. The limiting point on a factory WRX head is the cam. If you find a set of STi cams, plug the oiling holes on the intake cams and set the valve train up with some shimless buckets and you will be set!

And also, which block did you get? You mentioned it was an EJ25. Is it a 257 or a 255 block? They will have different compression pistons right off the bat. The EJ255 works with a D25 head and is 8.55:1 compression, the EJ257 had a B25 and VB25 head which makes 8.2:1. Easy way to tell is see if the pistons have one or dots indicating forward. And does your series block have the black nitride crank? If so, you lucked out as it looks like Subaru is phasing them back out.

Sorry to ramble on and cover the complete long block! Haha! Just my .02 on it.

[Samiam1017]

It's a 257 factory new short block. The crank is black. I haven't decided if I'm going to look for 2.5 heads or cnc the heads. Thx