30/12/2025
Factory Subaru blocks can fail here, but does this build have all the right fixes?
Subaru engines are often criticised for reliability once boost and power increase, particularly when the factory cast block begins to separate under load. Damien Brand of B-Sport gives us a detailed breakdown of a 1250kg 1999 Version 5 GC8 Subaru Impreza STI hill climb car that has been built with reliability as the primary goal, not headline power numbers.
This car uses a Crest CNC billet block and cylinder heads to address known Subaru issues such as main case fretting, uneven exhaust port flow, and limited clamping force. The engine produces 480kW at the wheels on 28 psi of boost using a BorgWarner 9280 turbocharger, deliberately operating well within the component limits.
Some of the supporting systems that make this package work in a hill climb environment are also covered, including an RCM dry sump system, a PBG six-speed sequential gearbox with rally-style push-pull paddle shift, and a full MoTeC electronics package featuring an M150 engine control unit, dual PDM30 power distribution modules, E8 expander, C125 display, and keypad.
The discussion focuses on why these choices matter for longevity, oil control, drivability, and data logging in hill climb competition, and why building a Subaru once and building it right is often the fastest approach in the long run, and after 10 years of effort, Damien certainly wants to get as much enjoyment as possible.
BorgWarner Boosted MoTeC TBT Wiring and Tuning
