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Old 11-27-2004, 04:09 PM   #1
JDM_Scobaru
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Default RS Heads vs. WRX heads

I am thinking about doing a Turbo Legacy Swap to my car, but I want to relplace the legacy heads with different better flowing heads. So how do the RS heads compare to the WRX heads in terms of flow.

Thanks,
Zach
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Old 11-27-2004, 04:50 PM   #2
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Zach,
Just wanted to let you know. I'll be in chicago after december 20th. If you would like to check out the head then you certainly can. I'll also give you a good deal because I need to empty my garage (the heads have both cams and should be perfectly fine, but they need to be cleaned and I would suggest replaceing the cams because I accidently droped one onto the floor.
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Old 11-27-2004, 06:51 PM   #3
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So how do WRX heads compare to RS heads?
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Old 11-28-2004, 03:37 PM   #4
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I have heard that the RS heads were some of subarus best flowing heads, but you may need to do a search on www.RS25.com, I know there are some threads about it there I remember reading awhile back.
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Old 01-04-2005, 11:03 PM   #5
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Quote:
Originally Posted by JDM_Scobaru
So how do WRX heads compare to RS heads?
good question.... Anyone???
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Old 01-05-2005, 12:09 AM   #6
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Zach, you still want these wrx heads?
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Old 01-05-2005, 12:11 AM   #7
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Quote:
Originally Posted by DoctorNick
Zach, you still want these wrx heads?
No thanks though i already gave a guy $5000 for a wrx swap in March, If anything changes though or plans dont go through Ill contact you.

Thanks again,
Zach
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Old 01-06-2005, 03:21 PM   #8
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There are two different verions of the 2.5 RS head. The first was the MY 1998 DOHC head that came on the 1998 RS. After that, Subaru changed over to a SOHC design for the remaining GC8 RS body style (through 2001). There was no increase in power as a result of the transition to the SOHC for the RS.

COBB is about the only company that has done any extensive work on the RS head. On the intake cycle, a BONE STOCK *SOHC RS head flows more air than a stock GM LS1 head. Quite impressive. The only problem that I have found with the SOHC RS head is that the cam profile is too small, netting a rather dramatic dropoff in power past 5500 RPM. However, a large turbo suited to high RPM power making can alleviate some of the fall-off that RS-T owners experience. A cam is another good option.

I have not seen any empirical evidence to suggest that the WRX head flows MORE than the RS head. I would imagine though, that it does have a more aggressive cam profile to lengthen the threshold of power fall-off as a result of the rather small turbo that the WRX comes with from the factory. However, I have not seen any benchflow statistics to prove that the WRX flows more. COBB would be a good source to research for factual evidence.

To say one is better is not entirely accurate. A lot of it depends on what you want to do. Both heads (with stock cams) have made VERY VERY impressive numbers on the dyno. For the RS head, one must look no further than how much power Mark R. (xephyr on the forum) has recently made in his 2.5 RS with the stock DOHC design heads. 452 WHP @ 21 psi.....The WRX has also pushed similar, and prob higher, power levels.

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Old 01-06-2005, 03:46 PM   #9
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hmm very informative
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Old 01-06-2005, 03:52 PM   #10
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RS heads can probably be had a bit cheaper and maybe more readily available. I would get RS heads personally, but in the end it probably won't make the hugest difference assuming a semi-realistic power goal for most daily drivers. My 2cents
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Old 01-06-2005, 04:24 PM   #11
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Hmm....Thanks everybody for the good input
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Old 01-06-2005, 04:55 PM   #12
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Quote:
Originally Posted by Graham
I have not seen any benchflow statistics to prove that the WRX flows more.
Neither have I.


Last edited by Wedge; 01-06-2005 at 05:18 PM.
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Old 01-06-2005, 05:57 PM   #13
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I was wondering when you were gonna step in wedge
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Old 01-06-2005, 06:15 PM   #14
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Hmm interesting results, what about a stage one for WRX heads?
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Old 01-06-2005, 06:27 PM   #15
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Vic- thanks for the information, quite helpful.

JDM- A stage one setup for the WRX would certainly improve airflow, but then again so would a stage one for the RS heads. Also, about 6 months ago I saw a dyno plot of a WRX that had done a cam swap to HKS 264's I believe. With something along the lines of a VF22 sized turbo, the power increase was ALL transferred to the upper RPM range. Yes, this would be fun if you want a car that is top-end heavy in the powerband, but that is not going to get you out of corners quickly on a race track. Thus, the whole argument goes back to what kind of application you are aiming for. A cammed, top-end happy WRX head would be wicked on the drag strip, but horrible for a road course where you want power down low. Also, depending on what size turbo you are using, having a medium range power cam in the car can aide spoolup tremendously versus a a high profile cam that only delivers power on the top-end.

Soon2beGreat- You hit the nail on the head...unless you hovering above the 400+ WHP range, I just don't think you find extremely noticeable differences between the two heads. Another factor is that assuming you have a GC8 chassis/ECU, you would have to wire in the WRX heads. RS heads are certainly easy to come by, and cheaper.


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Old 01-06-2005, 07:13 PM   #16
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Well in a little whie, I will have a JDM ej20 in my car, what cams would be an upgrade for the car?
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Old 01-06-2005, 07:14 PM   #17
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Also how hard is it to put cams in that motor, how long and what would have to be done?
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Old 01-06-2005, 07:17 PM   #18
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Jun 264 would be a nice medium.
Subarustore.com has cheaper cams, forgot who makes them.

Its a PITA, better do it while the motor is out. Did cams once in the RS, and thats much easier then the wrx.
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Old 01-06-2005, 07:33 PM   #19
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I think you should leave the stock cams in the car and save money on the cams you would have put in. Plus, I would not doubt it if the JDM cam profile was more aggressive than their USDM companions. But then again, it would be easy to do while you have the motor out of the car.


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Old 01-06-2005, 07:40 PM   #20
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RS heads: SOHC you gotta buy cams, DOHC, you have to oversize valves and port. Which bang are you going to take is the question i think...
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Old 01-06-2005, 07:46 PM   #21
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I hear the usdm sti cam is another option. Also more likely to find a set of those for a decient price with all the new deep pocket sti owners.
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Old 01-06-2005, 08:23 PM   #22
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Then what mod, if i choose to leave the JDM cams in, should i do, to the motor?
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Old 01-06-2005, 09:32 PM   #23
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What kinda JDM motor? G? K?

Honestly, if your getting an older JDm model, like V4 old, I would get cams. But I would just say just do the BPU mods (IC, samco hoses, TBE, Headers mabye?)
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Old 01-06-2005, 10:12 PM   #24
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its a JDMEJ20G
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Old 01-06-2005, 10:12 PM   #25
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I'd just leave the cams stock, just get basic stuff like exhaust and get the car tuned.
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