** Updated 24/02/2026 **

DISCLAIMER:

All information and opinions presented herein is to be used as nothing more than a general guide only. no responsibility will be taken for incorrect and outdated information, personal / property damage etc.

although care has been taken to research and check information as accurately as possible, please use it at your own risk.

if you think some information is incorrect, please Message me so i can rectify it.



After hours of searching throughout different forums, groups and pages, i noticed theres a lot of conflicting, missing and confusing information surrounding the differences between GC8 WRX and STI Valve Train designs, heads, flow and maximum HP, upgrade paths, Maximum RPM, failure points etc.

so in order to save myself and others a ton of headaches in the future when it comes to tracking down this info, i’d like to consolidate as much *accurate* information as possible!

For now this thread will focus on the EJ205 and EJ207 engines found in a variety of Version 5 and Version 6 WRX and WRX STI models. Although these engines do share some parts with the later model WRX GD, Forester and Legacy/Liberty models, all information presented in this thread is focusing on the GC8, GM8 and GF8 EJ20 models, although In future i hope to expand this thread to include the earlier EJ22T, EJ20G and EJ20K engines.



** More info wanted please **

• Head casting codes/types and identification
• dyno results of unmodified and modified EJ205 and EJ207 heads/valvetain, HP and RPM limits of factory components
• component power bottlenecks, limits and failures
• component interchangeability
• recommended upgrades
• measurements of cam profiles, valve weights, spring pressure etc.
• port size differences and head casting differs
• valve clearance settings
• anything else i’ve missed

the basics:



EJ205

Applies to:

• JDM GF8 WRX Wagon only
• AUDM GC8 and GF8 WRX
• EUDM/UKDM GC8 and GF8 Turbo 2000 etc.

Design:

Shim over bucket

Head Casting code:

WRX V5

Left: LH A 003 Right: RH A 003

WRX V6

Left: LH S20 Right: RH S20

Factory Rev Limiter:

7,000RPM

Intake Valve Head OD:

36mm

Exhaust Valve Head OD:

32mm

Intake Valve Length:

104.60mm

Exhaust Valve Length:

104.75mm

Intake Camshaft:

13031AA101

Exhaust Camshaft:

13034AA101

Intake valve:

13201AA390

Exhaust valve:

13202AA400

collet:

13210AA020

Valve spring:

13217AA193

Valve Spring retainer:

13209AA110

Valve Lifter:

13228AA031

Valve Spring Seat:

13227AA070

Valve Clearance Shims:

13218AExxx

13218AFxxx

13218AKxxx



EJ207



Applies to:

• JDM GC8 WRX Sedan
• JDM GC8 and GF8 WRX STI
• JDM GM8 WRX STI Type R
• JDM GC8 WRX STI Type RA

Design:

Shim under bucket

Head Casting codes:

WRX STI V5

Left: LH C 005 Right: RH C 006

WRX STI V6

Left: LH C 007 Right: RH C 008

WRX STI Type RA V6

Left: LH S20 Right: RH S20

Factory Rev Limiter:

7,500RPM (WRX)

8,000RPM (WRX STI and Type R + RA)

Intake Valve Head OD:

36mm

Exhaust Valve Head OD:

32mm

Intake & Exhaust Valve Stem OD:

5.97mm

Intake Valve Length:

105.9mm

Exhaust Valve Length:

104.75mm

Intake Camshaft:

13031AA160

Exhaust Camshaft:

13034AA160

Intake valve:

13201AA400

Exhaust valve:

13202AA410

collet:

13210AA020

Valve spring:

13217AA202

Valve Spring retainer:

13209AA110 (WRX)

13209AA120 (WRX STI & Type R)

Valve Lifter:

13228AA031 (WRX)

13228AA070 (WRX STI & Type R)

Valve Spring Seat:

13227AA070

Valve clearance shims:

13218ADxxx



Sources:

Part numbers and catalogs:

• https://subaru.epc-data.com

Head casting numbers:

• https://www.clubsub.org.nz/forum/index.php?/topic/41534-ej205-ej206-ej207-ej208-short-block-identification/

• https://www.type-ra.com/subaru-forum/threads/engine-id.28005/

general information:

thanks to @stockcar

 

Wait for Joe or Alyn on here to answer that one, or head over to Type RA forum

 

Best to contact Alyn-asperformance

 

in general terms an MY99/00 STi or STi RA engine uses shim UNDER bucket with specific (more aggressive) cams, retainers & springs to allow the higher rev limit against the more std SOB used in the WRX & UK Turbo2000 cars........
AVCS is specifically a "new-age" MY01> spec and was never factory std on any "classic" chassis.
"big port" is a term that applies to JDM 2.0 AVCS cars only........

most STi / STi RA cars whilst they are "safe" to the higher rev limit are often well past their power band and your simply revving for fun!!

 

also just to add the classic EJ207 bears no relation to the new-age spec EJ207
classic EJ205 & EJ207 use Open deck blocks whilst the new-age EJ207 is a Semi-Closed deck block as well as different crank, rods, pistons, etc dependant on exact age

 

@hedgecutter Mustn't want my advice Caleb

 

little typing = win win

 

thanks everyone for the input so far.
seems like i’m best to convert to SUB with aftermarket cams + springs & retainers if i actually want usable power past 7k rpm!

as some of you suggested i’ll also try contacting that shop you guys recommended and see what they have to say on the subject. hopefully im be able to post some reliable info when i find out.

in the meantime i've been comparing valve part numbers, and they are definitely different.

intake
EJ205: 13201AA390 EJ207: 13201AA400
Exhaust
EJ205: 13202AA400 EJ207: 13202AA410

cant confirm if they’re shorter or just lighter but definitely different in some way or another. interestingly enough if you put the EJ207 valves P/N into google it also cross references to later model subaru outback EJ205, so maybe the later models were upgraded to the lighter valves?same goes for the springs of course, they’re different between the 2 engines:

EJ205: 13217AA193 EJ207: 13217AA202

interesting stuff…

 

Stockcar above is AS Performance, first name Alyn.