Build Your LS with Summit Racing™ Pro LS Forged Pistons

No matter what type of LS engine combination you’re building, there is a Summit Racing™ Pro LS Forged Piston for it. They’re available for popular crank strokes, connecting rod lengths, and bore sizes, with compression ratios starting in the mid-9:1 range for boosted engines and up to 11.5:1 for naturally aspirated or nitrous-fed motors. Let’s see what makes a Pro LS piston tick.

Forging
Summit Racing Pro LS pistons are forged from 2618 alloy aluminum, chosen for its ductility and crack resistance. Careful attention was paid to the material thickness in the crown area to insure strength without creating excessive weight. The corner radii are large to increase strength in critical areas—weight saving was not a consideration here.

Wristpins
Summit Pro LS pistons are designed around a 2.250 inch long chromium steel wristpin. This pin length provides several advantages:
• No notching needed to clear the reluctor ring in stroker applications. This prevents cutting across the piston forging grain and creating a weak spot that can allow a crack to start
• The pin boss span is moved inboard and captures the factory connecting rod small-end perfectly. This reduces pin flex by putting it into shear rather than bending
• Forced pin oilers lube the pins with every down-stroke. The design maximizes bearing area for reduced pin bore wear

These features mean the piston and pin can be lighter, which reduces rotating assembly mass. Less rotating mass means less horsepower lost to spinning the assembly.

Piston Skirts
To compensate for thermal expansion, a piston must have the proper taper from top to bottom plus the right cam (oval shape) to compensate for the piston’s structure. Pro LS pistons have A skirt profile with the cam and taper required to ride perfectly in the bore. A premium skirt coating allows the pistons to run even tighter to the cylinder bore walls. A tighter fit means increased piston stability, less wear, increased piston ring seal for more power, and reduced piston slap.

The Pro LS pistons for stroker applications have a skirt taper that starts higher on the piston than other piston designs. This adds extra stability when the piston is at Bottom Dead Center (BDC) in the bore. This adds reduces piston skirt wear.

Ring Lands
The Number One cause of piston failure is ring land breakage, either from detonation or too-tight piston ring gaps. Pro LS pistons are designed to use thinner file-fit ring packs to maximize ring land thickness. The top ring land thickness is .275 inch minimum, with many Pro LS pistons having .300 inch thick top lands. Secondary ring lands are .165 inch thick and have a pressure seal groove for increased ring seal.

Other Features
• Pistons for 6.0L and larger engines have generous valve reliefs that work with both cathedral and rectangular port heads
• High-speed brush deburred to remove sharp edges that cause detonation
• Precision machined ring grooves cut with a slight positive angle for nd the valves and enhance combustion

Summit Racing Pro LS Forged Pistons are available in versions for Gen 3 press-fit, Gen 4 floating, and aftermarket 6.125 inch connecting rods. You can get more in-depth technical information and application charts in this Pro LS piston article on our OnAllCylinders blog. 

SEE SUMMIT RACING’S PRO LS FORGED PISTONS