Checking and repairing the block head and its parts

Check the flatness of the seating surface of the block head. To do this, attach a ruler diagonally to the head of the block and check with a feeler gauge that the ruler fits the surface of the head. Repeat measurements at different locations on the block head and on different diagonals.

The head of the block can be ground no more than 0.3 mm. The volume of the combustion chamber cannot be less than 38.88 cm³. If these requirements are not met, the block head must be replaced.

Check the camshaft bearing bores for signs of rubbing. The camshaft should rotate freely in the bearings, without jamming. A bent or damaged block head must be replaced with a new one. Slightly knocked-out valve seats can be attempted to be repaired using the appropriate tool kit (e.g. Hunger). But first you need to check the clearance of the valve stem in the guide. The method of this measurement is shown in fig. 2.70.



The gap measured in this way can be a maximum of 0.7 mm for the intake valve and 0.8 mm for the exhaust valve. If the gap is large, it is necessary to expand the guide to the next repair size (pic. 2.71). After that, it is necessary to select new valves with rods of increased diameters. The width of the chamfer of the valve disc should be:

	in 1.4i engines	in engines 1.1
intake valves	1.75 mm	1.18mm
exhaust valves	2.32 mm	1.75 mm

The upper angle of the cone of the working chamfer of both types of valves is 45°. The saddle top correction angle is 30°and the bottom correction angle is 75°. Before inserting into the seat, lubricate the working chamfer of the valve disc with a thin layer of fine-grained abrasive lapping paste. Enter the valve into the guide and install in the seat. Turn the valve several times. The contact surface will be visible on the working chamfer of the valve in the form of a matte ring, the width of which must correspond to the above values. Near the edge of the plate on the surface of the working chamfer should be visible "brilliant ring" 0.5 mm wide (pic. 2.72).



Under no circumstances should the valve face be ground separately from the seat. The only way to obtain an accurate fit of the working chamfer and seat is by diligent (time consuming) rubbing with appropriate tools.

The head of the block is installed in the reverse order to dismantling.