At one point it was rumored that the USDM Corollas had stiffer valves springs compared to the GR Yaris. We have recently proven this to be false. This should be the first engine modification done as it's the first limiting factor when tuning. Before the stock turbo is maxed out, valve float at high RPM occurs.
Here lies the "Drop in" solution. We highly suggest these to be installed by a professional.
Used Factory Retainers, Keepers and Seats
Supertech Spring Weights-
Intake- 90lb @ 42.6mm Seat Pressure (Closed) - 212lb @10mm (Open)
Exhaust- 90lb @ 42.6mm Seat Pressure (Closed) - 212lb @ 10mm (Open)
Max Net Lift- 17mm
Coil Bind - 25.6mm
Rate - 12.2 lb/mm
Stock Spring Weights-
Intake- 50lb - Seat Pressure (Closed)
Exhaust- 80lb Seat Pressure (Closed)
