A compressor assembly including a cylinder block defining first and second cavity portions. A central axis extends through first and second cavity portions. A compressible fluid respectively enters and exits the first cavity portion through an inlet and outlet. A piston is reciprocatingly disposed along the central axis and includes first and second piston portions which are at least partially disposed within the first and second cavity portions, respectively. The first piston portion defines a compression chamber within the first cavity portion. Reciprocation of the piston compresses the fluid within compression chamber. The second piston portion has a radial outer surface at least partially engageable with a sidewall of second cavity portion whereby forces transverse to the central axis are transferable between the radial outer surface and the sidewall. A variable volume space is defined by the second piston and cavity portions. A vent passage communicates with the variable volume space.