A furnace (10), firing pattern and method of operating a heater that employs a combination of hearth burners (46) and wall burners (56) for the cracking of hydrocarbons is described. The firing pattern leads to improvements in the uniformity of the coil metal (26) temperatures and vertical heat flux profiles over the firebox elevation. The hearth burners (46) operate with a stoichiometric excess of air while the wall burners (56) operate with less than the stoichiometric amount of air.