connecting holes 30 into the high pressure chamber 18 and finally is discharged from the discharge port 16 to the outside of the compressor a second embodiment shown in fig5 differs from the foregoing embodiment in that the compressor has an intake side at its front end and a discharge side at its rear end the compressor includes a front side block 7a which is replaceable with the rear side block 7b of the foregoing embodiment the front side block 7a includes a pair of intake holes 21a only one shown while a non illustrated rear block is provided with discharge holes a front head 11a of the compressor has an intake port 15 which is corresponding to the discharge port 16 of the compressor of the foregoing embodiment other structural details of the compressor are the same as those of the foregoing embodiment with the exception that a low pressure guide groove 20 is formed in the front head 11a instead of the drive shaft 4 the like or corresponding parts are indicated by the same reference characters throughout several views and due to the structural similarity a further description is not necessary according to a third embodiment shown in fig6 through 9 a sliding vane rotary compressor includes a displacement adjustment mechanism incorporated in a rear side block 7b and a rear head 11b the compressor of this embodiment is the same as the compressor of the first mentioned embodiment except the shape of the rear side block 7b and the internal construction of the rear side block 7b and the rear head 11b the displacement adjustment mechanism is the same in principle as the mechanism as shown in japanese utility model laid open publication no 55 2000.