Leading A-Series engine specialist since 1981
Our forged Omega 18cc has become the piston of choice for forced induction engines, available in plus-0.020" and 0.040" sizes with standard diameter 13/16" (20.6mm) gudgeon pins.
The large central dish allows for a much reduced compression ratio, all without using problematic decompression plates or very large combustion chambers in the cylinder head.
This, combined with the high strength of Omega forged pistons, makes these the ideal choice for high performance turbo and supercharged engines.
Please see the additional information tab for more detail and advice.
We would highly recommend purchasing an MED piston installation tool for trouble-free insertion to the bores.
Supplied as a balanced set of four with ring pack, which is also available separately (these particular pistons use a ring set from our diecast range).
The 18cc dished pistons have been designed specifically for forced induction engines, to significantly lower the compression ratio. They are the ultimate choice for anyone building a turbo/supercharged 1275 A-Series engine.
These pistons are supplied with 13/16" (20.6mm) diameter pins, as per our diecast Omega range, meaning they can be press-fitted to standard conrods. They will not suit the MED steel conrods.
If you'd prefer to run a fully-floating setup, your conrod little ends will need to be machined and re-bushed by a competant machine shop. We do not keep bushes for these size pins.
We would recommend a skirt clearance of 0.004", however different engine builders will have their own preferences.
The recommended ring gap is 0.010"-0.012".
Forged vs diecast
For low-boost applications, we also keep a diecast Omega piston with 10cc dish, in plus-0.020" and 0.040" sizes. These forged pistons are stronger and feature a larger dish, making them best suited to high performance usage.
High silicone alloy is first cut to billet size and the faces machined to a smooth finish. Each billet is pre-heated in an air-circulating furnace to a temperature close to the operating temperature of the piston crown, then compressed into a rough shape using Omega's in-house forge and custom-designed dies.
The specific temperature, together with tightly controlled speed of the forging process, gives a dense and very fine grain structure to the piston for high strength and superior fatigue life.
Any excess material is then removed before the forgings are heat-treated and wet blast cleaned. From here each piston is subject to a highly developed process of CNC machining, with constant measurement and quality control checks by experienced perfectionists.
Once final machining is complete, the pistons are engraved with a model and batch number, cleaned and sorted into matched weight sets. It's a time-consuming process to create such a high quality product, but the end results are well worthwhile.