Abstract: A multi-cylinder internal combustion engine cylinder block is formed with communication ports allowing communication between cylinders that, when assembled with pistons and a crankshaft, are 180.degree. out of phase. This allows the trapped mass of air beneath a piston to flow beneath a piston in a different cylinder 180.degree. out of phase. As a result, advancing and returning pistons are matched to effectively balance pressures.

Abstract: A plastic one-piece tubular clip has a base portion embedded in the bolt mounting hole of each of the holes of an engine oil pan gasket, and a tubular shaft portion that projects through the aligned holes of an oil pan rail and an oil pan reinforcing plate, and through which the oil pan mounting bolts are inserted, the tubular portion having internal ridges or teeth to grip the shank of the bolt with its head portion butting up against the bottom of the reinforcing plate to resiliently lock all the pieces together as a subassembly so that the oil pan can be easily assembled to the engine merely by raising the oil pan up against the crankcase with one hand and then pushing each one of the bolts up into their mounting holes and tightening the same with the other hand.