New modern style Pistons and rings

[82ACAUTOCRAFT]

Does anybody use new style pistons and rings on FE, I am talking about high silicone forged pistons and new slim ring designs like on the modular ford engine for example! This allows running much tighter clearance with the bores.

[jared1970]

I think Barry Rabotnick had a thread about this once. I think his research showed little if any gain in FEs with those parts. Maybe my memory's failing me, maybe it was a different topic, but I'm pretty sure I remember him saying that the observed gains in power and longevity didn't justify the extra cost.

[Barry_R]

Was not me.... I will definitely run some pretty thin rings in a race application. Usually calls for custom pistons - - an .043 top, an .043 and/or back cut 2nd, and a reduced radial wall oil ring will free up some true measurable power - often 20HP or more.

I usually just run conventional 1/16-1/16-3/16 ring packs in street engines though. There is power to be had in fancier stuff - but its not in proportion to the added cost for most guys. Depending on the quality of the machining oil consumption can be an issue - or it can actually be reduced. The custom pistons and swoopy rings will bump the build price by somewhere around $500.

No silicone in pistons

Many street oriented pistons will have silicon though - - it adds durability for skirt and ring grooves in high mileage applications (such as daily drivers). The racers usually use 2618 alloy which has greater high temperature strength - but no silicon. Its really a matter of the right alloy for the intended job. Most Cobras don't rack up enough miles for durability to come into play....

[jared1970]

Sorry, my mistake. I must be thinking of someone or something else.

[olddog]

Originally Posted by 82ACAUTOCRAFT

Does anybody use new style pistons and rings on FE, I am talking about high silicone forged pistons and new slim ring designs like on the modular ford engine for example! This allows running much tighter clearance with the bores.

The modular (and many modern) engines come with a cast piston of high silicone content (>20% if memory serves me). The word is escaping my mind, but it is something like hypoeutectic or hypereutectic. They are stronger than cast aluminum and have a much lower coefficient of thermal expansion. This gives a modestly strong piston that can be fit much closer to the bore.

A forged aluminum piston is the strongest. It is more dense, due to the forging process, but this also gives it the highest coefficient of thermal expansion. In very high performance applications (turbo-charged for example), the pistons must be fitted so loose, that when cold, there is often piston slap, until the engine is warmed up.