I was planning on installing the JDM V8 RA Spec-C Heads, but my tuner (Kingpin) convinced me to send my USDM STi heads to Cosworth Racing as core, for one of their fully-built heads.
I read on www.fastwrx.com that the Cosworth Racing 2.5L Heads flow 15% more @ Inlet Ports & 31% more @ Exhaust Ports, does anyone know how much more the JDM STi heads flow over the USDM STi heads?
Also, I was planning on using the DPR Stage 4 or 5 cams to take advantage of the higher redline (8500-9000+), and large turbine turbo (.85 or .95 A/R T4 Turbine/GT35R Comp.). The DPR Stg 4/5 cams are advertised as 323 & 330 duration (intake & exhaust) camshafts, whereas the JDM V8 RA Spec-C Cams are something like low 260 to high 260 duration cams w/ "Large Port" Heads. I'm highly doubting the duration is measured at the same point, does anyone know what the equivalent duration would be for the DPR & JDM cams?
Another plus about having my 2.5 Heads built for my 2.65L Sleeved (Large Bore & Stock Stroke) block is that the 2.5 Heads were designed for my bottom end, as compared to the 2.0L JDM Heads. Money saved from not having to get the JDM heads combustion chamber re-worked to match the bottom end. Also, the Cosworth Heads are ready to have the cams of my liking dropped right in.
Are the USDM Head castings completely different than the JDM STi heads? Since i'm going with the Autronic SM4 Standalone EMS, does anyone know if i'd be able to swap in the JDM V8 RA Spec-C Intake Manifold and bolt my 05' USDM STi's Drive-by-Wire Throttle Body on to it? Reasons for the swap: 1) JDM V8 RAC Intake Manifold uses "Top-Feed" Fuel Injectors 2) 1-pc "Long Runner" Manifold without TGV's
I read on www.fastwrx.com that the Cosworth Racing 2.5L Heads flow 15% more @ Inlet Ports & 31% more @ Exhaust Ports, does anyone know how much more the JDM STi heads flow over the USDM STi heads?
Also, I was planning on using the DPR Stage 4 or 5 cams to take advantage of the higher redline (8500-9000+), and large turbine turbo (.85 or .95 A/R T4 Turbine/GT35R Comp.). The DPR Stg 4/5 cams are advertised as 323 & 330 duration (intake & exhaust) camshafts, whereas the JDM V8 RA Spec-C Cams are something like low 260 to high 260 duration cams w/ "Large Port" Heads. I'm highly doubting the duration is measured at the same point, does anyone know what the equivalent duration would be for the DPR & JDM cams?
Another plus about having my 2.5 Heads built for my 2.65L Sleeved (Large Bore & Stock Stroke) block is that the 2.5 Heads were designed for my bottom end, as compared to the 2.0L JDM Heads. Money saved from not having to get the JDM heads combustion chamber re-worked to match the bottom end. Also, the Cosworth Heads are ready to have the cams of my liking dropped right in.
Are the USDM Head castings completely different than the JDM STi heads? Since i'm going with the Autronic SM4 Standalone EMS, does anyone know if i'd be able to swap in the JDM V8 RA Spec-C Intake Manifold and bolt my 05' USDM STi's Drive-by-Wire Throttle Body on to it? Reasons for the swap: 1) JDM V8 RAC Intake Manifold uses "Top-Feed" Fuel Injectors 2) 1-pc "Long Runner" Manifold without TGV's
