Apparatus and methods for processing substrates using a gas injector unit with a quartz plate are provided. The gas injector unit comprises an injector body with a first opening extending through the injector body. The first opening has a nut portion and a clamp portion. A nut is positioned within the nut portion spaced from the injector body by a spring. A clamp is positioned within the clamp portion, which may be remotely located on a hub for connection with the injector body. A screw extends through the opening in the clamp, a portion of the injector body, the spring and into a connection portion of the nut. Gas distribution assemblies and processing chambers incorporating the gas injector unit are also described.