911 SC port sizes
 

I hear that not all SCs were created equal in terms of injection port sizes. Can someone explain to me what differences exist between the various models? Also, what are the ramifications of these differences when it comes to tuning and power?

Thanks

Someone will chime in with the fine details but basically the 1978-1979 SC engines are considered " big port " which is good for horsepower. The 1980-1983 are considered " small port " which is better for torque.

Big ports were better for performance.

Small ports were better for emmissions and fuel economy.

ROW SC's maintained the big ports through 83 for exports to unrestricted emissions areas.

USA Specs:

1978-79 SC port sizes: I = 39mm/E = 35mm

1980-83 SC port sizes: I = 34mm/E = 35mm

All models used the same valve sizes: I = 49mm/E = 41.5mm