What heads

[Samiam1017]

Ok quick story. Bought 05. Got it. Blew up motor a few days later. Ya it sucks. It's was a wrx. I bought. Ej257 short block. I have a few options. Work my 2.0 heads to hybrid ready. Cost is gonna be around 1400 for machine work. Or source out stock heads. What heads will work. And a quick explanation of the differences. Legacy gt turbo heads? Any different than sti? I also want to change it over to fly by wire. Did that start in 06. Then I would need intake, ecu,harrness, throttle body right? Am I missing anything. Thanks

[Mechie3]

$1400 is a lot for machine work. I bought a set of 15k mile 09 WRX heads for $800 shipped (included cams, buckets, pulleys, valve covers, etc).

Don't do a hybrid. They're hard to tune and prone to detonation. A lot of teh benefit of the 2.5 motors come from the AVCS which is located on the heads of the 2.5 motors.

DBW was 04+ STI and 06+ WRX. Not sure about LGT.

06+ WRX heads and 04+ STI heads are different. STI are triangle shaped, WRX are hemispherical (D25 casting). It's believed the D25 casting is better for flow and combustion. WRX heads have a different volume, so if you put those on an ej257, you'll have odd compression ratios. ej255 and ej257 shortblocks are the same except for the pistons (to make up for difference in head volume).

[PhyrraM]

ALL 2.5 liter turbos were drive by wire (and AVCS).

Having the 2.0 heads CNCed to match the 2.5 combustion chamber removes the "hybrids are hard to tune" stigma.

To convert to DBW and/or AVCS you would need to replace (at least) the engine control parts of the harness. Considering that Subaru doesn't separate the engine parts from the rest of the car, you'll need a complete harness and then decide to "segregate and merge" or to just replace the whole thing.

[Maximus]

Which is why I hope they go ahead and offer harness options for us. DBW would be great to keep.

[Mechie3]

You also need a DBW intake manifold and throttle body. The 07 STI manifold was slightly different with respect to bolt locations for the TGV to manifold connection.

Yes, CNC matching the combustion chamber removes the stigma. If he's paying $1400 for total machine work (CNC work is only ~$400 from a dealer on NASIOC) though, he can by heads with AVCS for less money.

[PhyrraM]

....... If he's paying $1400 for total machine work (CNC work is only ~$400 from a dealer on NASIOC) though, he can by heads with AVCS for less money.

Only if the heads are fresh. If your talking a set of used, 50K mile AVCS heads vs. a full recondition - the playing field isn't really level. Rebuilding a set of AVCS heads will cost about the same, leaving only the $400 for CNCing the chamber as the difference.

[Mechie3]

I bought a set of 15k mile 09 WRX heads for $800 shipped (included cams, buckets, pulleys, valve covers, etc).

nd 06+ WRX. Not sure about LGT.



Only if the heads are fresh. If your talking a set of used, 50K mile AVCS heads vs. a full recondition - the playing field isn't really level. Rebuilding a set of AVCS heads will cost about the same, leaving only the $400 for CNCing the chamber as the difference.

Yes, they need to be fresh. I quoted myself for what I paid for a set. I did disassemble them, check them, and use valve grinding compound to seat the valves. They didn't need anything else (or seating, but they were already out, might as well).

I actually have a set of 06 heads I need to sell. I blew a head gasket with them and never had time (or the need) to do anything with them.

[Samiam1017]

The 1400 was to surface,valve job and a cnc port. I don't remember the shop or the break down but I can go thru my emails if anyone wants to know. Mechie. Can you get me a link to the other guy also what's the deal with you heads. Pm me. Im parting out the 05 and want to get one with DBW and aluminum lowers. So intake harrness and all the other happy stuff I need will be in there somewhere. Thx

[BrandonDrums]

I've been doing a bit of research on this myself. I have an '05 WRX which I had a semi-built EJ55 swapped in by a local shop. That engine died (thanks to the local shop cutting some really bad corners) and now I'm about to swap a stock 07 STI engine in there. Long-term, I'm just trying to figure out which heads I should use for my fully built engine if/when the used 07 engine I put in looses compression.

I'm pretty sure the EJ255 heads are better. The EJ255 is more or less the same in the 06+ wrx and the 05+ Legacy GT and Forester XT and uses the B25 Heads which many builders think are superior to the STI heads. Slightly higher compression, better, more hemispheric combustion chamber and less intake and exhaust port angles. Because of the better shaped combustion chamber, you counter the increased risk for knock from the increased compression over the STI heads supposedly when you run STI spec pistons (which are lower compression than the EJ255 pistons)

This is by far the most in-depth and most amazing breakdown of the differences between the STI (Ej257) vs, every other turbo 2.5 (Ej255) heads out there. The bottom end between the 257 and 255 are the same besides pistons. STI's are lower compression with a bit more ideal crown shape, everything else is identical in the bottm.
http://forums.nasioc.com/forums/showthread.php?t=1856856

Also, AVCS is neat but is not so fancy you can't live without it. You have 4 options for your 2.5L swap into your WRX

1: Plug the oil holes on the Cams and run your solid non avcs WRX cam pulleys and just leave the solenoid wires unplugged (you wont have them on a pre '06 wrx harness and ECU) This is the most ideal non AVCS setup, the WRX cams are lighter and there's no questioning any 'float' in advancing or retarding valve timing since they are solid.

2: Do a TGV delete (http://forums.nasioc.com/forums/showthread.php?t=1663677) and swap in a JDM V6-V8 16 bit ECU which run cable throttles just like the 2.0L wrx and you can then just re-splice in 4 wires to use the TGV plugs (http://forums.nasioc.com/forums/showthread.php?t=2285827) to run the AVCS instead. This grants you AVCS control without having to swap or splice the entire wiring harness and convert to drive by wire control to get AVCS abilities. However, you will have to swap back to the original ECU to pass emissions (the JDM ECU isn't compliant with US OBD requirements) so you'll have to do some opensource tuning on 2 separate ECU's. Not bad though.

3: **This one won't be a logical option for the OP since he's buying heads separately, he'll likely already have the cam gears off.
Only leave the AVCS solenoids unplugged, leave everything else from the AVCS system in tact on the engine and run the OEM ECU. I'm doing this for my engine swap, most say the AVCS stays in its default position with the solenoid unplugged, some say there's up to a few degrees of "float" where the AVCS cams just move around because there's nothing controlling them. Mechanically, I don't believe there to be any way they can float without the solenoids being activated so they run like solid cams but are just heavier and have some oil flowing to them but not through the channel that will cause them to move.

4: Swap in the full mechanical AVCS system AND convert the full ECU and wiring harness from an AVCS enabled car. **That requires swapping throttle bodies, changing the throttle pedal linkage, full ECU and engine harness swap. Not worth it IMO. Either run without AVCS, convert to a JDM ECU or if you want the extra ~10 ft-lbs of torque below 2500 rpm but aren't willing to mess with electrical stuff, swap the cams with upgraded non-avcs units.

For options 1-3 you will need a cosworth Cam Position Sensor adapter bracket and you'll need to plug the 2.5L's rear camp position sensor ports (and most likely some air-pump ports depending on the year heads you get).

Here's a great write-up on how to swap in a 2.5L to a wrx
http://elementtuning.com/technical/ej25_install.htm

Here's info about the air pump delete:
http://forums.nasioc.com/forums/showthread.php?t=1209260&highlight=air+pump+removal

[rjh2pd]

TGV delete +1. I would think that if you could run AVCS then you should. It will gain you power either up high or down low (depending on cams). Running without it would be like someone deactivating VTEC.

[fateo66]

This is by far the most in-depth and most amazing breakdown of the differences between the STI (Ej257) vs, every other turbo 2.5 (Ej255) heads out there. The bottom end between the 257 and 255 are the same besides pistons. STI's are lower compression with a bit more ideal crown shape, everything else is identical in the bottm.
http://forums.nasioc.com/forums/showthread.php?t=1856856

Also, AVCS is neat but is not so fancy you can't live without it. You have 4 options for your 2.5L swap into your WRX

1: Plug the oil holes on the Cams and run your solid non avcs WRX cam pulleys and just leave the solenoid wires unplugged (you wont have them on a pre '06 wrx harness and ECU) This is the most ideal non AVCS setup, the WRX cams are lighter and there's no questioning any 'float' in advancing or retarding valve timing since they are solid.

I'm glad you liked my thread. If anyone wants measurements or other photos let me know.

As for the wrx cams, I believe what Brandon meant to say was the cam gears are lighter since the two intake gears are plastic as opposed to the heave mechanical AVCS aluminum/ steel ones. All 2.5 AVCS cams are hollow in some manner, the later ones quite a bit more so then the early 04-05 ones. So if you want some pretty nice OEM heads on your DBC car run D25's with some 06+ AVCS cams (they are more agressive then 02-05 WRX ones.)

Or you can do what I plan on doing on my second build and run some SOHC Z25 castings :cool:

[BrandonDrums]

TGV delete +1. I would think that if you could run AVCS then you should. It will gain you power either up high or down low (depending on cams). Running without it would be like someone deactivating VTEC.

Not really that big of a difference. AVCS on Subarus are literally only active until about 3000 rpm on the stock tune yielding just an extra 10-15 ft-lbs of torque at the flywheel down at the bottom end of the revs. It can be more with a tune but out of the factory the main benefit is efficiency, emissions and a little fight against turbo lag.

The USDM 2.0L turbo engine lack any variable valve timing and they run great. Having driven my 2.5L swapped wrx without AVCS and compared it to my friend's similarly tuned STI, any losses in torque down low that I missed out on I re-gained by doing a hybrid boost control setup which does a lot to minimize turbo lag.

AVCS would of course make the down-low grunt even better but I'd say the most work it's worth is just doing the JDM ECU swap on the stock harness.

And yes, i did mean to say the WRX non-avcs cam pulleys are lighter, the cams themselves I don't know about.

[Samiam1017]

Wow lots to read now. Thx. I have a lead on a 05 legacy gt and that's why I asked about them heads. So they are B25 heads. Are the ones ill looks for if I don't get the whole car. Brandon. You mention above in option one. The use of none AVCS cams out of 2.0 wrx heads. Are you suggesting. The B25 heads and use my current cams? Just so it's out there I'm not looking for 500 hp unstreetable hp. To just trying to have a good strong canyon carving motor. Thx again for the links now on to more reading.

[PhyrraM]

....... Just so it's out there I'm not looking for 500 hp unstreetable hp. To just trying to have a good strong canyon carving motor. ......

I would think that any stock turbo motor would be more than sufficient. :cool: Add a Tactrix cable and a tune for a cheap upgrade if your 'ego' (not meant to be derogitory, just descriptive) needs more than a 'stock' motor for something as cool as the 818.

[Mechie3]

Here's a thread showing the difference between 2.0 heads on a 2.5 block vs a cnc'd 2.0 head on a 2.5 block.

http://forums.nasioc.com/forums/showthread.php?t=2017993

[BrandonDrums]

Wow lots to read now. Thx. I have a lead on a 05 legacy gt and that's why I asked about them heads. So they are B25 heads. Are the ones ill looks for if I don't get the whole car. Brandon. You mention above in option one. The use of none AVCS cams out of 2.0 wrx heads. Are you suggesting. The B25 heads and use my current cams? Just so it's out there I'm not looking for 500 hp unstreetable hp. To just trying to have a good strong canyon carving motor. Thx again for the links now on to more reading.

I actually meant "Cam gears" not cams,I need to revise that post. The engine I'm taking out of my WRX is just a rebuilt 05 legacy GT engine with B25 heads with the cams from the B25 but the cam gears from my 2.0L wrx engine. Any 2.5L cams will be better than the cams from a 2.0L with or without AVCS but you can swap the cams themselves if you want.

I loved that engine up until it died and i will be rebuilding it for future use.

If you end up getting the 05 Legacy GT you'll be perfectly happy. If you aren't concerned about max power, you can't go wrong really with any 2.5L turbo engine, they'll all comfortably make 300whp reliably if treated properly.

[Samiam1017]

I ended up buying an 02 wrx. But I think I'm just gonna part it out and look for an 06. Or heads. Or both. Pm sent to mechie

[Samiam1017]

I think I narrowed my heads down to d25 06 avcs heads. New questions. I've seen a lot of tear down threads but nothing really like an assembly manual thread and reassembly of the motor from short block. Something with info like assembly order, torque specs, what to lock tight and what not to lock tight, what's recommended to be replaced or upgraded. Would help out greatly. I would gladly do a build thread with somebody walking me thru it. If that would indeed help out others too.

[Samiam1017]

Brandon you mentioned using the tvg wires to run the avcs. What is needed to make this happen. Is there any down sides to this? Would I be able to use my 05 harness. I guess the ecu is out and I would need to source a Jdm? Thx for your help

[Rasmus]

I recommend the FSM. Flying Spaghetti Monster. No, wait. Wrong FSM. Factory Service Manual. Assembly order. Torque specs and sequences. Drawings.

[Evan78]

Anyone interested in service manuals should take a look at this website:

http://ken-gilbert.com/impreza-manuals

[Mechie3]

That doesn't work for all years and is STI specific. Some torques may be different for your model year.

EDIT: My bad, he's updated his site. Used to have only the 04 STI manual. I have the full 06WRX/STI manual in PDF form so haven't looked for it elsewhere.

[Samiam1017]

Ok I'm getting closer to being able to assemble my motor. Ej257 with 06 wrx d25 heads. I have the heads coming. I already have water pump, gates timing kit, what else off hand am gonna need before I start to assemble to a long block. My list. Gasket set, oil pump,oil cooler( I guess these aren't cleanable as I had a bearing issue and would rather not use as is) head bolts,??? Any suggestions on these? Is there a place to get a complete gasket kit minus the short block stuff I don't need. Also it's an 06 block/ head but I'm using all 05 assessories. Will all the gaskets work from one kit or do I need to piece meal it together.

[Mechie3]

A gasket kit from an 06 should work. The master gasket set from Subaru is probably your best best. The only shortblock stuff you'd be left over with are a couple o-rings. All the other gaskets are for bolting on heads and accessories.

I measured the small bolts that hold the dorito triangle piece to the AVCS cam. It's an M5x.8, 9.5mm length from underside of head to end of threads, but ~2.5mm of that is taken up by a split lock washer and a plain washer.

[Tim@ajwperformance]

Ok I'm getting closer to being able to assemble my motor. Ej257 with 06 wrx d25 heads. I have the heads coming. I already have water pump, gates timing kit, what else off hand am gonna need before I start to assemble to a long block. My list. Gasket set, oil pump,oil cooler( I guess these aren't cleanable as I had a bearing issue and would rather not use as is) head bolts,??? Any suggestions on these? Is there a place to get a complete gasket kit minus the short block stuff I don't need. Also it's an 06 block/ head but I'm using all 05 assessories. Will all the gaskets work from one kit or do I need to piece meal it together.

The 06 Gasket kit will work just fine. Id definitely recommend new head studs whether you use OEM or ARPs, the studs tend to stretch a bit on turbocharged models. OEM 11mm STi oil pumps are a nice upgrade for you. Definitely check the oil pick up tube thoroughly as well for any cracks that may be there

[Samiam1017]

Tim do you guys sell factory Subaru stuff? I'm putting a list together and should be ready soon. At what power level would you recommend ARP bolts over factory. I thinks its only about hundred bucks but I like to keep my money to myself if possible.

[BrandonDrums]

Brandon you mentioned using the tvg wires to run the avcs. What is needed to make this happen. Is there any down sides to this? Would I be able to use my 05 harness. I guess the ecu is out and I would need to source a Jdm? Thx for your help

Hey Samiam1017, sorry for the late reply. You'd need just a V7 JDM STI ECU (wow, lots of acronyms) and the rest of the how-to information is here.

http://forums.nasioc.com/forums/showthread.php?t=2285827

I've never done this myself, I'm considering it but I think even with this simple work-around it's probably not worth the effort. Keeping AVCS disabled and upgrading the cams would be easier frankly.

However, it's a cool trick for folks who want the benefits of AVCS for a more street friendly setup.

FYI, I'm going to be selling a set of V25B heads (from an 07 STI) here in the next couple of months if anyone is interested!

[Samiam1017]

I got my heads in. Real nice looking 40000 mile d25 heads. I think now I have two options. Option one use the Jdm v7 ecu to run the avcs. And do a tvg delete (which I planned on anyway). Option two spend the money I was gonna spend on a ecu and get a set of cams and run without avcs. What everybody's opinion on what they would do/recommend and what the benefits/down falls of both options. My Main concern is tuning options. What's gonna be easiest to have tuned. Also what turbo should I look to get for quick spool up. I would like an upgrade from the stock td04 I have

[Samiam1017]

I'm gonna bump this up instead of starting a new thread. I'm looking for the proper ecu. Brandon recommends Jdm ver7 to control the avcs thru the factory tvgs controls. Question is whats the part number for a version 7 Jdm ecu. I see one offered on nasioc but I want to make sure it's the right numbers. A search shows it is but also had a guy mention the last 3 digits as 481 which this isn't. Better to be safe then sorry. Thx

[fateo66]

Just out of curiosity I wonder if you can use a USDM 02-05 ECU and flash in the JDM ROM along with wire up the AVCS solenoids like they would be on the JDM WRX. Some one smarter then me over on NASIOC might know.

[Samiam1017]

Sound logical right. I guess I will search around. I've never seen it mentioned before when I have run across threads on the topic