Product development (PD) and engineering design processes are often characterized by the information flowing among activities. In PD, this flow forms a complex activity web a process that can be viewed as a complex system. Most literature on the subject of information flow in PD focuses on a single project, where precedence information constraints (based solely on necessary information and possible assumptions) determine the execution sequence for the activities and the resultant project lead-time. In this paper, we consider multiple PD projects that share a common set of design resources. Especially in this setting, precedence information availability is insufficient to assure that activities will execute on time. We extend the information flow modeling literature by including resource availability. We model several PD projects as a portfolio, where activity execution is based on both information and resource availability. We demonstrate the effects of accounting for resource constraints on both individual projects and portfolio lead-time distributions.