A sealing arrangement for a post for an intake manifold having a first portion and a second portion held together is set forth. Each of the portions extends from a shell half that, when the two shells are attached to one another, form the intake manifold. Each of the portions includes a face. A groove is formed on at least one of the portions. A seal is fitted in the groove. A fastener hole is formed in the portions. In one portion, the fastener hole passes through the portion and in the other a thread is formed by a thread forming fastener. The seal may be positioned in a groove formed on a post face, in a groove formed adjacent the opening of the fastener-receiving hole in the post, or in a groove formed on an interior wall of the post adjacent a cap fitted over the head of the thread forming fastener.