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Piston Material Comparisons

Junes Mopar Muscle Magazine has a great article on differing types of Pistons, and their suggested usage. I'll try to convey what they are in a short as possible post.

Cast Aluminum
-Best suited for stock engines (no HP given)
-Lower priced

- The typical cast piston is melted, and poured into a steel mold having the shape of the finished product. This requires minimal machining. They are less expensive and designed as a cost effective replacement option.
As such they are not well suited for high performance engines.

Hypereutectic (Cast) Aluminum
-Best suited for up to roughly 600 to 650 HP in normally aspirated engines.
-Middle of the road pricing.
-This type of piston is also a cast piston, but with Silicon added roughly 16%. This produces a harder more wear resistant version of the standard cast piston. Silicon expands less then aluminum because it also acts as an insulator preventing the aluminum from absorbing as much as the operational heat as a standard cast piston. It is also harder and is less susceptible to scuffing. Also this piston allows closer piston to sidewall clearances improving combustion seal do to less rocking as it travels in the
cylinder.
- Because of the higher silicon content it is a less ductile alloy and is less forgiving when used in boosted and/or nitrous applications. Best suited for normally aspirated engines. (Just a guess, this may be what is in our 6.4s)

4032 Forged Aluminum Pistons

-Best suited for engines producing up to 1,000 HP normally aspirated
-Higher priced
-Forged Pistons are the strongest on the market. Manufactured by forcing a hot aluminum ingot into a simple mold. This results in more machining to produce a finished product. 4032 alloy is a high-silicon alloy with low expansion characteristics. Pistons of this alloy can use tighter piston to wall clearance with tighter seal and less noise and reduced scuffing then the 2618 cousin. Less scuffing and piston rocking.
-Again because of the higher silicon content it is less ductile it is less forgiving when using boosted and/or nitrous applications. They have a lower resistance to detonation. Best suited for minimal amounts of boost or normal aspiration.

2618 Forged Aluminum Pistons
-Best suited for engines producing up to 1200 HP and ideal for running power adders.
-Higher Priced (so what else is new?)
-This Piston a lower Silicon content (2%). Thus it exhibits high expansion characteristics. Typically used for extreme duty racing applications. 2618 pistons are engineered to use larger piston to wall clearances. This means when you start the car the pistons will be heard when cold. Commonly called piston slap. Once the engine heats up the slapping noise will quiet as the piston expands.
-2618 is a more ductile alloy and gives a higher resistance to detonation.
These characteristics enable the pistons to survive some of the most extreme conditions, but longevity is eventually compromised after countless heat cycles.

<phew> article from June 2014 Mopar Muscle Magazine
 

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great info - thanks!
 
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