ARP HEAD STUD FIXING KITS
( £108.33 EXC VAT )
Our Forced Induction Special forged piston now comes with a huge 18cc central dish to lower the compression for forced induction engine applications.
These utilise the standard-size 13/16" gudgeon pin with circlips for a fully-floating little end and will require machining and re-bushing of the conrod by a suitable machine shop. Alternatively we can supply these with a standard press-fit pin. Please see options above.
Available in plus-0.020" and 0.040" size, which have proved to be the most popular with forced induction engine builds.
Why use 18cc forged pistons?
Our range of Omega forged pistons are stronger yet lighter than our diecast range, making them particularly well suited to high performance applications. The 18cc dished pistons have been designed specifically for forced induction engines to significantly lower the compression ratio and are the ultimate choice for anyone building a turbo/supercharged 1275 A-Series engine.
Which gudgeon pins do I need?
Our forged pistons tend use an 18mm pin for fully-floating little ends, but these particular pistons are fitted with larger 13/16" (20.6mm) pins for extra strength, making them ideal for high-boost applications. If using standard conrods, the little ends will need to be machined and re-bushed by a competant machine shop.
Alternatively we can supply regular length gudgeon pins for press-fitment. Of course, some forced induction/race engines will be using steel 'rods - in which case we would recommend the MED Steel conrods with 20.6mm little ends to run these pistons fully floating.
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: