Using a Stant LEV-R-VENT radiator cap is like using Speed Bleeder bleed screws for the first time, a revelation. By gently raising the lever, the radiator Pressure is gradually released. No more steam and boiling water escaping when you open the cap on a hot engine... 0.5 bar (7psi) relief Pressure.
 
Part Name: Stant Lev-R-Vent Radiator Cap, 7Lbs (0.5Bar)
AlfaStop Product Code: 1CS152
Original Alfa Romeo Part No: 1365.64.020
Model: Guilia 101 Series, Giulietta 750 & 101
Quantity Per Car: 1