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Old 03-26-2008, 09:08 PM   #1
Scooby Newbie
Member#: 31707
Join Date: Jan 2003
Location: Los Angeles,CA
1995 Open Class
GC rally car

Default Help! Simple guy needs simple answers re:Hybrids!

Hey all,

There seems to be some conflicting info here that I want to try to get straight.

I have a GC rally car with a blown WRX motor (2 actually). Both motors have melted pistons that have scored the cylinder walls so I am looking to either -
1. Bore out cylinders (giving me an oversized 2.0), install forged pistons and rods, slap on WRX heads which are in good shape.
2. Replace with a brand new 2.0 WRX shortblock, slap on the WRX heads I already have.
3. Replace with a brand new STi shortblock, slap on the WRX heads I already have.

I'm leaning towards #3 since the STi shortblock would have the larger displacement and (supposedly) better internals.

Here are my questions...

Does the USDM STi block have forged rods AND pistons? (I have read something here that appeared to say it does NOT have forged pistons and that the STi pistons are the weak link)

Do the WRX heads bolt straight up to the STi block with no problems? (I have read some rumblings about valve clearances)

Does the STi block bolt straight up to the WRX 5MT transmission with no problems? (I'd assume we use the WRX flywheel)

Can the stock WRX injectors handle the demands of the larger displacement block? (already have a Walbro 255 pump)

What is the hot setup for a hybrid build that would not be on the ragged edge of destruction, bearing in mind it is going into a rally car and needs to be fairly driveable?

At this stage I don't want to drop multi thousands of dollars on an engine, so I'm looking to use as much of what we already have ie turbo, TMIC etc...

Like I said there is such a huge volume of info here that I am working my way through it is difficult to keep everything straight.

Thanks in advance for any and all help and opinions.
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Old 03-27-2008, 11:05 AM   #2
Scooby Specialist
Member#: 86274
Join Date: May 2005
Chapter/Region: MAIC
Location: Crofton, MD
. Andrewtech
Gold Club Member


I would bo with option 3 as well. The STi sb is not that much more expensive than the WRX sb.

The EJ257 has forged rods and cast pistons. The pistons are the weak link but if the car is tuned properly, you shouldn't have any issues.

WRX heads do bolt right up. All you need is the 2.5L head gasket.

It does bolt up to the WRX transmission.

It would be a good idea to upgrade the injectors. You would be maxing out the stock ones and it would be nice to have bigger injectors if you decide to get a bigger turbo.

If you want something that would be perfect for rally go with a smaller turbo. A stock td04 would spool instantly and yeild decent power. When I had hybrid tuned with the stock td04 I hit 260 whp and 282 wtq. Then I put in a modded td04 (ported, polished, 16G compresser wheel, clipped exhaust wheel) and bumped the power up to 290whp and 309 wtq. There was instand throttle response and I kept on thinking what an amazing rally setup this would be. It ran out of power around 5500 but all you needed to do is shift and it would be back. It had plenty of useable power.
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Old 03-27-2008, 12:05 PM   #3
Scooby Newbie
Member#: 31707
Join Date: Jan 2003
Location: Los Angeles,CA
1995 Open Class
GC rally car


Perfect reply. Thanks for that.

NicktheBrit is offline   Reply With Quote
Old 03-27-2008, 12:05 PM   #4
Element Tuning
Former Vendor
Member#: 54918
Join Date: Feb 2004
Chapter/Region: MAIC
Location: Gaithersburg, MD
673 WHP Element
Tuning Pro Comp Engine


It really depends on your budget but let's say you have $2k.

While the STi short block is a great bottom end it's dismal on the top when mated to WRX heads and cams. If you swap the cams to STi or better and this turns into an awesome setup.

I would say get new WRX 2.0 block haves or find some used in good condition. $900
Shameless plug: Element Tuning Forged H-beam rods $549
Forged Pistons with rings: CP for instance $650
Bearings: $170
Subaru Engine Gasket kit: $300
ARP Head Studs: $200

Your parts total $2119.

This is assuming you could build it yourself but this motor would work best with the factory heads plus with the gasket kit you can replace all your seals etc.

Now if both of those blown engines are out of your car then you need to solve the cause of the failures before you invest in an new engine as it will blow up just as easily as the first two if you have a bad tune or a fuel injector/manifold leak which is usually what causes a melted piston.

Good luck.
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