metal frame 19 is secured by bolts 21 to a flange of the block 1 the two frames 19 and 20 partially overlap and between the overlapping portions there lies a resonance absorbing or insulating resilient flexible element 2 the element 2 is bonded as by vulcanizing or adhesive securing to the frames 19 20 and extends continuously therebetween the element 2 also serves as a continuous oil seal between the crankcase 3 and the block 1 the mounting is therefore a compact assembly the composite casing 3 3 39 is rigidly connected to a gear box 4 by a bolted flange the cylinder block 1 head 12 and auxiliaries 13 are enclosed an a non oil wetted sound proofing cover 5 5 39 the main part 5 of the cover is secured to the crankcase 3 through the frame 20 and the bolts 22 the top of the cover 5 39 is connected to the main part 5 through an edge frame 25 of angle section the cylinder block 1 head 2 and crankshaft 9 are all connected to the crankcase 3 through the resilient element 2 bonded to the frame members 19 and 20 so that during operation of the engine movement relative to the gear box 4 can occur a flexible rotary coupling 8 is therefore.