Greeting from Oregon~The shower me state,

Just bought (buying) our first home at 50 years old. Better late than never I reckon. It has an older Tappan range~no external model number found. Both upper and lower oven coils glow bright and hot but the oven will only reach 375 on preheat, while the vent under the left rear burner is putting out enough heat to simmer water in a pot. What's goin' on with this?