bolts 29 wherein the length of the flat edge is longer than the outer diameter of the shank of the locking bolts 29 there are two long hollow bushings 33 disposed at the cylinder head cover 30 wherein the flat edges of each oval shape pipe hole 31 are perpendicularly installed each other in order to fasten the two long hollow bushings 33 and the cylinder head cover 30 onto the cylinder head a plurality of assembling bushings 35 are formed at the cylinder head cover 30 for insertion of the locking bolts 29 the assembling bushings 35 are designed to absorb deformation and manufacturing defects of the cylinder head cover 30 in relation to the cylinder head by forming a hole having a diameter larger than that of the shank of the locking bolts 29 but smaller than that of the head as described in the first embodiment the assembly method of the engine cylinder head cover 30 thus described can be applied in almost the same method as the first embodiment the only difference is that in the assembly method thus described step s 1 is substituted with a step for provisionally assembling the locking bolts 29 using any one of two long hollow bushing 33 the remaining steps can be initially applied to the assembly method thus described as in the first embodiment as apparent from the foregoing there is an advantage in the engine cylinder head cover and assembly method thereof according to the present invention in that the disposition and arrangement of a cylinder head cover in relation to a cylinder head can be constantly maintained by a simplified assembly method there is also another advantage in that the locking bolts for installing a cylinder.