Blocks and cylinder liners

Machining of small and large-size engine blocks is done primarily using the machines from the Danish company, AMC-Schou, and the American company, Sunnen. Boring (honing) of cylinders and surface planing is carried out with high-precision boring machines for high machining parameters.
JURGAL uses modern honing technology for rebuilding of engine blocks. Engine block honing is performed to obtain correct grinding and eliminate any excess material resulting from hole boring using a traditional boring machine. The blocks are subject to this operation after initial grinding. Thanks to the honing, the block is properly prepared for nominal or oversized pistons.

Cylinder honing, also known as cross grinding or finishing, is a state-of-the-art technology for the surface treatment of metals. We perform it using a digitally controlled honing machine, which guarantees the required technical parameters of the cylinder bearing surface, responsible for proper engine lubrication etc. Cylinder honing is carried out using honing heads equipped with diamond whetstones. In addition, we use lubricating and cooling liquids to transfer away the heat energy generated during the treatment process and remove the honed material away from the abrasive stone and the workpiece.

Honing using a CNC-controlled honing machine has many advantages, the greatest of which is the certainty that each cylinder is precisely machined according to pre-programmed parameters. As a result of this process, each cylinder is shaped in an optimal way, without errors (e.g. ovality, axis curvature, scratches, concentricity or waviness). Errors of this type cause much faster wear of cylinder surfaces, and the displacement of the rings in the piston grooves or leaks past the rings, which may cause the fuel to get into the oil. This error is highly undesirable as it considerably deteriorates the lubricating properties of the oil.

The honing of cylinders is also performed to give their surface a honing pattern. The scratches crossing at the right angle help to distribute and hold the oil on their surface, thanks to which it is properly separated from the ring and the piston. This is used for avoiding friction of these parts during operation, which significantly extends their service life.

The technology utilised by JURGAL guarantees that the required hole parameters are repeatedly obtained. Thanks to this modern technology, it is possible to minimise errors in the shape of the machined hole. During honing, the surface becomes free of geometric errors, such as: distortions, microcracks and scratches. This process also adjusts the geometry of the cylinder, whose wear makes it conical and oval. Compared to the bored surface, honed workpieces are given longer service life and better lubricating properties.

Rebuilding of the block bed plate is based on restoring the dimensions of the holes for the crankshaft supports in accordance with the catalogue data while maintaining their concentricity. A horizontal boring machine and a horizontal honing machine are used for machining the crankshaft bearings.

In the case of seizure of the crankshaft supports, we can restore them by welding. One of the operations in the rebuilding of engine blocks is alignment with a horizontal boring machine. The alignment of an internal combustion engine block depends on the concentricity and dimensions of the crankshaft bed plate in the engine block. It should be done when:

• the crankshaft has broken,
• the engine has been severely overheated,
• the crankshaft is seized on the main bearings of the shaft,
• after assembling the crankshaft on new bearings, it rotates heavily or sticks,
• there are other faults affecting the shaft.

Aligning of the engine block involves corrective boring of the main bearings of the crankshaft, and if necessary, hardfacing of any defects in the seats and coaxial boring of the entire bed plate in the block.

In some cases, it might be necessary to replace all the bearing surfaces in the engine block. This means replacement of the cylinder liners in the engine block in those situations where the cylinder bearing surface is damaged so severely that grinding cannot be performed. This is also used when oversized pistons are not available for purchase. Replacing the liners in the engine block allows us to preserve the original pistons.