The engine has two cylinder heads. Each head is centered by two locking pins pressed into the cylinder block

The cylinder heads are fitted with guide bushings and valve seats.

Valve bushings are metal-ceramic. Inlet valve bush inner diameter 9+0.022mm, and exhaust 11+0.022mm.

The allowable wear of the bore of the valve guides must not exceed 0.05 mm. If the inner diameter of the bushing increases, it should be replaced.

For spare parts, valves are produced in a standard size, and bushings are produced with an inner diameter reduced by 0.3 mm, i.e. with a reaming allowance after being pressed into the cylinder head.

The worn bushing is pressed out with a punch. A new bushing is pressed in with a thrust mandrel from the side of the rocker arms.

The sleeve above the plane for the valve spring should protrude no more than 22 mm.

After pressing, the valve sleeve bore is reamed to the appropriate standard size.

The valve seats are made of cast iron.

Small defects in the working surface of the seat can be eliminated by grinding the valve to the seat, and deep scratches and other large defects can be eliminated by grinding the seat, followed by grinding the valve to the seat.

The tightness of the valve seat in the seat also depends on the concentricity of the seat face and the guide sleeve bore.

The concentricity of the seat is measured with an indicator device.

The base is the hole in the valve guide, and the indicator foot slides over the seat.

The non-concentricity allowed without repair should not exceed 0.06 mm.

When replacing the valve seats, they are removed using carbide countersinks.

Before installing the repair size saddle, its seat in the cylinder head is bored to the following sizes:

For inlet valve seat 49.25+0.027mm and exhaust —- 38.75+0.027mm.

Before being pressed into the cylinder head, the seats and valve guides are cooled in solid carbon dioxide (dry ice), and the cylinder head is heated to 160-175°C.

Cold seats and bushings during assembly should enter the seats of the heated cylinder head freely or with little effort.

Under light blows of a hammer on the mandrel, the valve seat and sleeve should sit in place.

In no case should you hammer in a seat or bushing with great effort, as this will disturb the fit, and later, when the engine is running, the seat or bushing may fall out of its socket.

The operation of installing seats and bushings in the cylinder head must be carried out quickly.

When the temperatures equalize, large interferences appear in this connection, under which further pressing is impossible without great effort.

To grind the working chamfers of the newly installed seats concentrically with the holes in the valve guides. To do this, use a special device.

The spreading reference is installed in the machined hole of the bushing, and the mandrel shank serves as the axis for the grinding wheel (driven by an electric motor) with a chamfer at an angle of 45°.

When grinding, the concentricity of the working chamfer of the seat and the valve sleeve hole of 0.03 mm (according to the indicator) should be ensured.

The cylinder head entering the assembly must be thoroughly washed, the cooling jacket must be cleaned of scale and dirt, the oil channels must be free of sludge, and the exhaust channels must be free of carbon deposits.

The valve guides pressed into the head of the block must be nominal or one of the repair sizes and marked with paint. The sizes of bushings and their marking are specified in tab. 1.

The distance from the upper end of the guide bush to the plane of the head should be 24 mm.

Inlet and exhaust valve seats must be ground at 45° to the axis of the guide bushings.

The width of the working chamfer of the seat should be 1.5 - 2.0 mm.

The runout of the conical surfaces of all valve seats relative to the axes of the holes in the valve guide bushings is no more than 0.025 mm.

The outer diameter of the valve guides pressed into the cylinder head can be of a nominal size or a repair one (increased by 0.25 mm).

Nominal and repair dimensions of the valve guide




or reduce

diameter, mm


Inner diameter

guide sleeve

valve, mm





1st repair




2nd repair




Inlet and outlet valves

Nominal and repair dimensions of valve stems




or reduce

diameter, mm


rod diameter, mm








1st repair





2nd repair





The diameters of the valve stems must be nominal or one of the repair sizes given in the table.

The working chamfer of the valve head must be ground at an angle of 45° to the axis of the stem.

The cleanliness of the working surface of the chamfer after grinding must correspond to the 8th grade.

Beating of the working surface of the chamfer relative to the valve stem is not more than 0.03 mm.

Cylinder head assembly and installation

Before installation, the valves and holes of the guide bushings must be thoroughly wiped.

Valves with nominal or oversized stems must be installed in guide bushings of the appropriate size.

The valves must be lapped into the seats in the cylinder head before assembly.

Lapping with paste, consisting of one part of M20 micropowder GOST 3647-59 and two parts of industrial oil 20 (spindle).

After lapping, the working chamfers of valves and seats should have a continuous matte contact strip with a width of at least ½ of the width of the seat chamfer around the entire circumference.

Lapped valves are numbered according to their seats and are not depersonalized afterwards.

After lapping, the parts must be thoroughly rinsed.

The quality of the lapping must be checked for leaks (at an overpressure of 0.05 kg/cm2, the amount of air let through by the valve can be no more than 12 cm3 per minute).

The order of tightening the cylinder head studs GAZ-66, GAZ- 53

The order of arrangement of the studs for fastening the racks of the axis of the rocker arms and the exhaust pipe:

а) studs of racks M10x1 L=112 mm - two extreme ones;

studs racks M10x1 L= 80 mm - two medium;

b) intake manifold studs:

  • extreme M10x1 L=30 mm;
  • medium M10x1 L=42 mm.

Before installing the cylinder head assembly with valves and exhaust pipe, the head mounting studs must be screwed into the block until it stops in the order indicated in fig. 1 and table.

The cylinder head gasket must be free of cracks and asbestos chipping.

Before setting, the head must be thoroughly blown out with compressed air.

The cylinder head must be freely put on the studs without impact and installed on two pins.

When tightening the cylinder head stud nuts, follow the order shown in fig. 1.

The nuts are tightened in two steps, preliminary and finally.

The tightening torque should be in the range of 7.3-7.8 kgm.

Final tightening should be done on a cold engine.

After a hot run-in and the engine has completely cooled down, check the tightening torque, which should be 7.3-7.8 kgm.

When tightening the cylinder head nuts, loosen the intake manifold nuts.

Cylinder Head Stud Installation Order



in order










in the left row




and its number













Assembly and installation of the axle with rocker arms and racks

Before assembling, thoroughly clean the inner cavity of the rocker shaft from sludge, dirt, etc. and blow it with compressed air. Wipe the outer surface with a napkin and grease with a thin layer of spindle oil.

The assembled rocker arms on the axle should turn freely without jamming.

The adjusting screw must be freely screwed into the rocker without jamming.

Setting the TDC of a GAZ-53 car

Mount rocker axles with rocker arms and uprights assemblies on the studs of the head of the block so that the heads of the pusher rods enter the rocker sockets.

The clearance between the valves and the rocker arm on a cold engine should be within 0.25-0.30 mm.

Adjust the clearance in the following order: turn the crankshaft to the position corresponding to c. m.t. compression stroke in the first cylinder, for which:

  • - close the hole for the spark plug of the first cylinder with your finger, turn the crankshaft until the compressed air starts to escape from under the finger. This will happen at the beginning of the compression stroke;
  • - carefully turn the crankshaft until the marks on the crankshaft pulley coincide with the central mark of the indicator c. m.t. (Fig. 2), located on the front cover of the block, and adjust the gaps between the valves and rocker arms of the first cylinder.

Then, turning the crankshaft 90˚ each time, adjust the valve clearances of the remaining seven cylinders in the order of their operation 5-4-2-6-3-7 and 8.

GAZ-66 TDC installation