The block of cylinders is cast from aluminum alloy and makes a single whole with the top part of a case. The block has the cavity of a water shirt opened up in which pig-iron sleeves with a support are inserted into a bottom of this cavity.

On a contour of the top plane of the block ten lugs for fastening of a head of cylinders are located. The lower (crankcase) part of the block is divided into four compartments by cross partitions in which radical bearings of a bent shaft are installed. Covers of radical bearings are made of malleable cast iron; each cover fastens to the block two hairpins with a diameter of 12 mm. In the first cover end faces are processed together with the block for installation of washers of the persistent bearing. Covers of bearings are chiseled assembled with the block and therefore at repair they should be established on the places. For simplification of installation on all covers, except the first and fifth, their serial numbers are beaten out. Nuts of hairpins of fastening of covers drag on a dynamometer key with the moment of 100 — 110 N · m (10 — 11 kgfs · l) also are stopped by Unigerm-9 sealant. To a forward end face of the block on paronitovy laying the cover of distributive gear wheels cast from aluminum alloy with a rubber cuff for consolidation of a sock of a bent shaft fastens.

To a back end face of the block six bolts and two adjusting pins the case of coupling cast from aluminum alloy which exact installation is necessary for the correct operation of the transmission fastens. The back end face of a case of coupling and an opening in it for installation of the transmission for the purpose of ensuring coaxiality of a main shaft of the transmission with a bent shaft are processed assembled with the block therefore the specified details are not interchanged.

Cylinders of the engine are executed in the form of the easily removable wet sleeves cast from special wearproof cast iron. The sleeve of cylinders is inserted into a block nest by the lower part. In the plane of the lower joint the sleeve is condensed with laying from soft copper 0,3 mm thick, and on the top end face — laying of a head of cylinders. For appropriate consolidation the top end face of a sleeve acts over the block plane on 0,02 — 0,1 mm. At the same time copper laying has to be pressed out. It is necessary for reliable consolidation that the difference of a vystupaniye of sleeves over the block plane on one engine was within 0,02 — 0,055 mm. It is reached (at the plant) by sorting of sleeves of cylinders according to height (from the lower joint to the top end face) and blocks on pro-point depth under a sleeve (from its top end face) on two groups. When changing sleeves of cylinders uniformity of a vystupaniye can be provided with selection of copper laying of the corresponding thickness.

   The head of cylinders — the general for all cylinders, is cast from aluminum alloy and subjected to heat treatment (training and aging). Inlet and final channels are executed separately for each cylinder and located on the right side of a head. Nests for valves are rowed on a longitudinal axis of the engine. Saddles of all valves — plug-in, are made of heat resisting cast iron of high hardness. Thanks to a big tightness when landing a saddle in a head nest (at the plant before assembly the head heats up to temperature of 160 — 175 °C, and saddles are cooled approximately to minus 40 — 45 °C, at the same time the saddle is freely inserted into a head nest), and also reliable and strong landing of a saddle in a nest is provided to rather big coefficient of linear expansion of material of a saddle. In addition head metal around saddles is pressed out by means of a mandrel.

Plugs of valves as well as saddles, gather with the head which is previously heated (plugs — cooled). Facets in saddles and openings in plugs are processed assembled with a head.

The head of cylinders fastens to the block ten steel hairpins with a diameter of 12 mm. Under nuts of hairpins the flat steel thermostrengthened washers are put. Between a head and the block laying from the asbestos cloth reinforced by a metal framework and covered with graphite is established. Windows in laying under combustion chambers and an opening of the oil channel are edged by a tin. Laying thickness in the compressed state — 1,5 mm.

The correct provision of a head on the block is provided with two adjusting pins plugs pressed in the block of cylinders (in lugs of hairpins of fastening of a head). Moment of force of an inhaling of nuts of fastening of cooking has to be 83 — 90 N · m (8,3 — 9,0 kgfs · м).

Heads of cylinders of engines 4025 and 4026 differ on the volume of cameras of combustion. Increase in extent of compression of the engine 4026 is received for the account of additional milling of the lower plane of a head on 3,6 mm (height of a head of the engine 4026 makes 94,4 mm, height of a head of the engine of 4025 — 98 mm).

Combustion chamber volume at the valves put into place and the screwed candle makes 74 — 77 ^cm3 for ^{the cm3} engine 4026 and 94 — 98 for the engine 4025. The difference between volumes of combustion chambers of one head should not exceed 2 ^cm3.