We have investigated the chemical equilibration of the parton distributions in collisions of two heavy nuclei assuming the partonic fluid to be ideal as well as viscous. The initial conditions are taken from HIJING calculations for Au + Au collisions at RHIC and LHC energies. It is seen that when the viscous drag is taken into account, the lifetime of the plasma is increased by a factor of nearly two. The temperature as well as fugacities evolve more slowly than their ideal counterpart. Photon and lepton pair production are also investigated. With viscosity, there is a twofold increase in the photon and lepton pair production. The increase in the large p_T photons or large invariant mass lepton pairs is due to the slower rate of temperature evolution.