OMEGA FORGED PISTONS 73.5mm - VARIOUS SHORT HEIGHTS

In Stock

£525.00

( £437.50 EXC VAT )

Various compression heights are available – 1.426", 1.248", or super short 1.115". This enables the use of our long conrods along with long-stroke crankshafts for ultimate performance.

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£525.00

( £437.50 EXC VAT )

The Omega/MED forged lightweight piston comes with a narrow-section ring pack, which will reduce friction, and the special ultra–light 18mm gudgeon pin. The pistons come complete with little end bushes to fit to the conrods, to make the gudgeon pins fully floating (see Technical tab), along with special wire circlips to hold the pins in place.

Various compression heights are available – 1.426", 1.248", or super short 1.115". This enables the use of our long conrods along with long-stroke crankshafts for ultimate performance. See the Additional Information tab for more detail.

With a standard 81.33mm stroke crank this will create 1380cc on a 1275 engine.

Supplied as a set of four with ring pack, which is also available separately. We would also highly recommend purchasing an MED piston installation tool for easy trouble-free insertion.

Why upgrade to forged pistons?
Our range of Omega forged pistons are stronger yet lighter than our diecast range, making them particularly well suited to higher performance applications. Forged pistons utilise a smaller, lighter 18mm gudgeon pin and bushes to convert the conrod little ends to a fully-floating configuration. Fully-floating pins give less chance of damaging the pistons on insertion, as with press-fit, and are easier to disassemble. Therefore it's the favourite method for competition engines.

Short or standard height?
This depends entirely on your desired engine setup. Short height refers to the distance between the centre line of the gudgeon pin and the piston crown top. These particular pistons are commonly used in conjunction with longer conrods and long-stroke crankshafts. Some engine builders use these to position the piston tops further down the bores, to perfect the compression ratio in certain applications, or allow more material to be skimmed from the top of the block. Standard compression height is 1.498".

What size pistons do I need?
Bore size remains one of the most common questions we're asked here at MED – should I go plus-0.020" for 1293cc or straight to 73.5mm for 1380cc? It's not as straightfoward as it first seems; you may be restricted by regulations to a set capacity, or the engine itself may have already been bored to a larger size. It may have even been bored, then re-linered again. In light of ever-increasing values of core 1275 engines, for cost-conscious engine builders we would recommend boring to the next size up where possible. A larger capacity should produce more power for a given engine spec, however, you may wish to keep a couple more bites of the cherry in hand, so to speak. Where maximum performance is the goal, 1380cc is the way to go.  

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.

Tech info for conversion to fully floating con rods:

  1. Fit supplied bushes to little ends and hone to a finished size of 18.015mm-18.020mm.
  2. Machine little end of conrod on the short side to give a finished width of 21mm
  3. Drill 1/8" hole through the little end and bush at the top of the conrod and lightly countersink to allow oil feed to gudgeon pin. 

 

Piston ring installation: