The block of cylinders is cast from an aluminium alloy and makes a single whole with the top part картера. The block has the cavity of a water shirt opened upwards in which with a support pig-iron sleeves 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. Bottom (картерная) the block part is divided into four compartments by cross-section partitions in which radical bearings of a cranked shaft are established. Covers of radical bearings are made of malleable cast iron; each cover fastens to the block two hairpins in 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 in gathering with the block and consequently at repair they should be established on the places. For simplification of installation on all covers, except the first and the fifth, their serial numbers are beaten out. Nuts of hairpins of fastening of covers are tightened динамометрическим by a key with the moment 100—110 Н·м (10 11 кгс·м) and stopped by hermetic "Unigerm-9". To a forward end face of the block on паронитовой to a lining the cover of distributive gear wheels cast from an aluminium alloy with a rubber cuff for consolidation of a sock of a cranked shaft fastens.

To a back end face of the block six bolts and two adjusting pins fastens cast of an aluminium alloy картер the couplings which exact installation is necessary for correct work of a transmission. A back end face картера couplings and an aperture in it for installation of a transmission for the purpose of maintenance соосности a primary shaft of a transmission with cranked shaft are processed in gathering with the block, therefore the specified details are not interchangeable.

Engine cylinders are executed in the form of the easily removable wet sleeves cast from special wearproof pig-iron. The sleeve of cylinders is inserted into a nest of the block by the bottom part. In a plane of the bottom joint the sleeve is condensed by a lining from soft copper in the thickness of 0,3 mm, and on the top end face — a lining of a head of cylinders. For appropriate consolidation the top end face of a sleeve acts over a block plane on 0,02—0,1 mm. Thus the copper lining should be pressed out. For reliable consolidation it is necessary, that the difference выступания sleeves over a block plane on one engine was within 0,02—0,055 mm. It is reached (at factory) by sorting of sleeves of cylinders according to height (from the bottom joint to the top end face) and blocks on depth проточки under a sleeve (from its top end face) on two groups. At change of sleeves of cylinders выступания it is possible to provide uniformity with selection of copper linings of a corresponding thickness.

   The head of cylinders — the general for all cylinders, is cast from an aluminium alloy and subjected heat treatment (to training and ageing). 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 pig-iron of high hardness. Thanks to the big tightness at saddle landing in a head nest (at factory before assemblage the head heats up to temperature 160—175 ° With, and saddles are cooled approximately to a minus 40 45 ° With, thus the saddle is freely inserted into a head nest), and also to big enough factor of linear expansion of a material of a saddle reliable and strong landing of a saddle in a nest is provided. In addition head metal round saddles is pressed out with the help оправки.

Plugs of valves the same as also saddles, gather with a head preliminary нагретой (plugs — cooled). Facets in saddles and apertures in plugs are processed in gathering with a head.

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

Correct position of a head on the block is provided with two adjusting pins-plugs, запрессованными in the block of cylinders (in lugs of hairpins of fastening of a head). The moment of force of an inhaling of nuts of fastening of cooking should be 83—90 Н·м (8,3—9,0 кгс·м).

Heads of cylinders of engines 4025 and 4026 differ on volume камep combustion. The increase in degree of compression of the engine 4026 is received for the account additional фрезеровки the bottom plane of a head on 3,6 mm (the height of a head of the engine 4026 makes 94,4 mm, height of a head of the engine 4025 — 98 mm).

The volume of the chamber of combustion at the valves put into place and the screwed candle makes 74—77 sm ³ for the engine of 4026 and 94—98 sm ³ for the engine 4025. The difference between volumes of chambers of combustion of one head should not exceed 2 sm ³.