There are many Ferrea springs available for B-Series. We only list the ones that we will use in our own engines for the applications that you all are using your engines in. Regardless of their descriptions, we highly recommend the S10086 spring (Kit 4036) for any all motor street or turbo application. They can be used for high hp turbo applications in the 1000hp range, and up to 10,000 rpm. If you require a heavier duty spring for more power and RPM please use the 4 Piston SFWD spring.
KT4001 - S10070 - Seat Pressure 80 lb, Max Lift 14mm
KT4002 - S10027 - Seat Pressure 100 lb, Max Lift 13.5mm
KT4027 - S10104 - Seat Pressure 80 lb Max Lift 13.5
KT4036 - S10086 - Seat Pressure 110 lb, Max Lift 13mm (Recommended by 4P for most applications)