Holley Fuel Cell Cap 241-228 | Looking for an alternative to your stock fuel cell cap or maybe you need a fill cap for that custom oil tank or valve cover you are building? Well, look no further! Holley has created a full line of Billet Fuel Cell Caps and Billet Fill Caps. Holley’s caps are CNC machined from 6061-T6 billet aluminum and they are bright black anodized for great looks and corrosion protection. Each cap features a laser etched “Holley Equipped” logo so you know quality is built in.