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Old 09-11-2007, 12:13 PM   #1
dubya-R-ex
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Default Recommendation needed: 2.5 or 2.0 WRX heads better for engine build? (NON-AVCS)

I am in the midst of doing an engine build with an STi short-block to go into my WRX. I intend on running non-AVCS. Which is the better choice of heads? 2.5L or 2.0L WRX heads? I plan on porting and building the heads and pretty much going all out with the APS tumbler deletes, port and polish 20G most likely, perhaps a 30R. Just curious which provides the better platform for an engine build and which provides the most potential. Please speak with experience if you are going to respond. Thanks!
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Old 09-11-2007, 02:13 PM   #2
PaulRex
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dont forget about 2.0l sti heads (v7/8), i dont think they are too expensive if compared to the 2.5l sti heads so consider those as well.

i only have a 2.0l so i cant really comment on these heads on a 2.5l since i dont have first hand experience just wanted to throw another option at you
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Old 09-11-2007, 03:22 PM   #3
Freon
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You really should get AVCS working if at all possible.
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Old 09-11-2007, 03:53 PM   #4
MindzeyeWRX02
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Quote:
Originally Posted by Freon View Post
You really should get AVCS working if at all possible.
very expensive to run AVCS.

If you can get 2.5L heads, go with those. If you don't have enough $$$ then the least you should do is upgrade the cams.

I am running an STi shorty with my 2.0L wrx heads. I have great torque but power falls off a little past 5k rpm. With upgraded cams, you should be able to have good power through out the power band.

just my .02
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Old 09-11-2007, 06:16 PM   #5
dubya-R-ex
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Quote:
Originally Posted by MindzeyeWRX02 View Post
very expensive to run AVCS.

If you can get 2.5L heads, go with those. If you don't have enough $$$ then the least you should do is upgrade the cams.

I am running an STi shorty with my 2.0L wrx heads. I have great torque but power falls off a little past 5k rpm. With upgraded cams, you should be able to have good power through out the power band.

just my .02

This is the type of response that I was looking for! Not some crap about recommending JDM heads. I don't intend on changing the ECU.

Upgraded cams and port/polish are planned. I am just wondering what the better base is for these upgrades. Simple enough I thought.
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Old 09-11-2007, 07:12 PM   #6
Texy32
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Default heads

Wrx's heads can flow just as well with porting and polishing. I second the cam upgrade. i had a hybrid 2.5/ 2.0 heads. it does flatten out unless you PnP the heads and upgrade the cams. There is someone on here now sell wrx race cams for $400. which is a steal. Make sure you run a line from the extra oil vent on the top of the 2.5 block to one of the heads.
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Old 09-12-2007, 01:36 AM   #7
bakka
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I have a built 2.5 bottom, p/p wrx heads, valves, springs and retainers with crower stage 3 cams.The car made 469 whp on pump gas. High compression makes it pull very hard.
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Old 09-12-2007, 01:39 AM   #8
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Quote:
Originally Posted by bakka View Post
I have a built 2.5 bottom, p/p wrx heads, valves, springs and retainers with crower stage 3 cams.The car made 469 whp on pump gas. High compression makes it pull very hard.
Turbo?

The one thing I wish I could've done over for my engine was to throw on a set of cams...
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Old 09-12-2007, 02:29 AM   #9
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Quote:
Originally Posted by bakka View Post
.... High compression makes it pull very hard.
What is your compression numbers? 8.7:1 or higher?

Last edited by wrxdaddy; 09-12-2007 at 09:19 AM.
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Old 09-12-2007, 12:54 PM   #10
Junior2JZ
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Bakka has standard STI head gaskets and 2.0 built WRX heads. Turbo is a FP 3065. The car hauls major ass
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Old 09-13-2007, 09:52 PM   #11
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USDM WRX (2.0) and USDM STi have identical ports but the STi has a slightly larger combustion chamber. It's very easy to have the chamber enlarged on the 2.0 heads to keep compression down and still use the proper sized head gasket (piston to head clearance should never exceed 1.2mm) if that's what you're interested in. Keep in mind the higher CR will help retain low end torque with the ported heads and larger cams - and spool a turbo faster.
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Old 03-28-2011, 08:56 AM   #12
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what kind of hp can I expect to get from a non built sti SB and wrx heads with the chamber enlarged to match the sti heads, running all stock internals?
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Old 03-29-2011, 03:02 PM   #13
soobaviator
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The S20 heads will give you the most flexibility to port for your application. They are small port to start with but have enough meat to enlarge to the same size as JDM big port heads.

I went huge on mines:





-soobaviator

Last edited by soobaviator; 06-15-2011 at 10:36 AM.
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Old 03-29-2011, 04:01 PM   #14
FuJi K
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Quote:
Originally Posted by akaerik21 View Post
what kind of hp can I expect to get from a non built sti SB and wrx heads with the chamber enlarged to match the sti heads, running all stock internals?
hp is on your turbo choice and fuel.

expect it to be like an STi head running on stock wrx cams, less lift.
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Old 03-29-2011, 04:29 PM   #15
OrbitalEllipses
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You'll want to at least pick up STI cams and plug them if not upgrade to something like a Kelford 264 or bigger.
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Old 03-29-2011, 09:17 PM   #16
theotherguy
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I have a set of ported B25 heads that have been modified for non avcs. Plugged sti cams, wrx cam sensor mounted, you'll need new seals. Too lazy to rewire the hydra in my '95 so I'm going to run the phase 1 dohc heads that are in it on a ej257. PM me if interested.
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