In Stock


( £437.50 EXC VAT )

New to our range of Omega pistons, the all new forged 998 semi slipper piston, CNC machined from lightweight alloy forgings.

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( £437.50 EXC VAT )

The Omega forged 998 semi-slipper piston is perfect for high performance small-bore engines, the plus 0.020" proving to be particularly successful in the Mini Se7en race series, with multiple race and championship wins.

CNC machined from lightweight alloy forgings, the pistons have been designed to be as light as possible, at only 236 grams for the 020 including 5/8" pin and rings.

For use with either fixed or fully floating pins and supplied with a set of special wire circlips. Spare forged 998 ring sets are also available and in stock.

Production process
The production of piston forgings is more complex than the casting process and some 80% of Omega's pistons are produced in this way. The main material used is RR58 (2618A). Two other alloys are used - one is a high silicon alloy and the other is a Metal Matrix Composite alloy.

The forging process requires material to be bought in at closely controlled diameters, this is then cut to billet size and all cut faces machined to a smooth finish. The billet is pre-heated in an air-circulating furnace to a temperature quite close to the operating temperature of the piston crown when the engine is operating at full power. This temperature is critical and cannot be disclosed.

This together with tightly controlled speed of the forging process gives a dense and very fine grain structure to the forging. Microstructure analysis of Omega's forgings and that of other manufacturers will highlight this difference. This fine grain structure gives the forgings higher strength and fatigue life. After forging, any excess material is removed and the forgings are then heat-treated followed by wet blast cleaning.

Piston ring installation: