James’ Show-spec GC8 gets a big power EJ20 with EFR7670


James’ GC8 was a show-stopper in its past life, and a failed engine made for a great excuse to install a power plant to do the car justice.

Back in the 2000’s when the Autosalon days were in full swing, huge wide-body conversions, shaved panels and big chrome wheels were all the rage.

Somewhere, somehow, someone got a hold of a high-performing version 3 WRX STI RA and went to town and turned it into a big baby blue show-stopper. The glory days of this style had well and truely past when James got ahold of the car. After a few good drives, the engine was also history.

To give the car a new lease on life, James teamed up with the PBMS team and setabout ditching the 20 inch chromies and building a high-tech engine package.


To piece together a strong engine that can handle far more than factory intended, factory block was binned in favour of a closed deck EJ20 item. This then had the full catalogue of parts thrown at it, with a stroker 79mm crankshaft with matching pistons and rods to increase the engine size.

EJ20 Stroker with EFR7670 twisted turboEJ20 stroker 2.14L (aka 2.2L)

  • PBMS prepped block
  • Oil gallery modification
  • 79mm Crankshaft
  • Eagle Forged rods
  • JE Stroker Forged Pistons
  • Group N Race Bearing
  • 12mm Oil Pump


Cylinder head technology has advanced since 1997 when the car was produced. For this engine we opted to use later model STI heads with intake AVCS (variable valve timing). This would allow for a wider power band and more response – ideal for driving on the road or track.

To improve flow, the PBMS Stage 2 port and polish was used in conjunction with Kelford cams and valve springs.

James' GC8 WRX STI RA Engine bay

High flow V7 STI heads

  • PBMS stage 2 port and polish
  • Kelford 272 camshafts
  • Kelford valve springs
  • ARP Head studs
  • Camshafts dialled in and balanced

Turbo upgrade

Continuing with the response and power theme started by the stroker engine and later model heads, we reached straight for the high tech EFR7670 turbo. This was coupled with a twin scroll exhaust housing (1.05 AR) and Turbosmart 45mm watergate.


Borg Warner ERF7670 PBMS twisted turboThe entire exhaust manifold was ditched in favour for a twin scroll variant, again to bring the power on early. A PBMS twisted turbo adapted was used to hold the ERF7670 in place.

ECU and EFI components

The RA has received a simple and effective setup to control the engine and supply fuel.

  • Link ECU G4+ plug in ECU
  • Bosch 1000cc Injectors
  • Walbro 465 intank fuel pump
  • Tomei Type L fuel pressure regulator
  • Split fuel rails


Moving to later model heads meant the factory Version 3 intake manifold would no longer fit. We chose to use a high flowing and impressive looking OE Subaru intake manifold off a Legacy. This wasn’t a simple bolt-on, however has proven to flow well across the rev range. Other extras such as a custom 100mm thick intercooler kit and downpipe were fabricated as part of the package.


Jame’s STI is amazing to drive on the road. The engine package works incredibly well together to give a very smooth and responsive package, achieving full boost as early as 3800rpm on the road, with power growing as the revs increase.

Built EJ20 Stroker with EFR7670

On the dyno it made 345kw on pump 98 at 29psi. The future will likely see a switch to E85, once the transmission has been upgraded to suit. We’re pretty sure that even in its current state, the big engine package finally does the body justice.

About the author, Julius

Julius provides technical support and expertise to Possum Bourne Motorsport. He's been involved with the industry since 2009 and has stamped his mark as an industry leader.


  1. Michael Wilkins on 12/21/2018 at 2:09 AM

    How good, I was the someone who originally built that car. But that engine and gearbox would have been toast after I sold it and moved overseas. Great to see someone put a new heart in it. I sunk that much cash into pre GFC then sold it during the GFC for a $40k loss. It’s a shame the carbon bucket seats I put in got taken out. Looks like the tein type flex adjustables are still in it.

    • Julius Bloem on 03/14/2019 at 7:04 PM

      Hey Michael, awesome build! When it turned up to us it had factory seats which we replaced with Bride seats. The original Teins had also expired, so it has a brand new set, as well as host of upgraded arms and bushes through out. This car is definately being well looked after, and drives like a dream!

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