A portable electrically operated gas heater for heating gases for use in curing sand molds. An electrical heating element fits tightly inside a bore in a heat exchange tube having sufficient mass for providing a reservoir for storage of a substantial amount of heat. The heat exchange tube is provided with fins on its outside and an inner shell fits around the fins to define a gas heating passage. An insulative outer shell is secured to the outside of the inner shell. An inlet port to the passage is provided for receiving cold gas from a pressurized source through a control valve and an outlet port from the passage is provided for distributing the gas after contact with the heat exchange fins in the passage. An automatic reset timer is connected to the control valve and is operative to open the valve for a predetermined period of time to deliver a burst of gas. Heater control means including a thermostat is provided for controlling the energization of the heating element to maintain a predetermined tempertaure within the gas heating passage. The heater control means is operable independently of the timer for continual energization of the heating element, under control of the thermostat, to store heat in the reservoir prior to delivery of a burst of gas by the timer. This storage of heat permits the use of a lower wattage heating element than would otherwise be necessary in order to instantaneously heat the burst of gas.