Primary advantage is the tip hardness which is 50RC as per Volvo specification.
Typical aftermarket valves are made from 21 4N stainless, which can only attain a tip hardness of 25RC unless a stellite wafer tip is added.
Tip is a critical wear point, having the additional hardness is good insurance.
CAR MODEL ENGINE INFO
Volvo Amazon B20 Intake, 42 mm
Volvo P1800 B20 Intake, 42 mm
Volvo 140 B20 Intake, 42 mm
Volvo 164 B30 Intake, 42 mm
Volvo 240 B20, B30 Intake, 42 mm
