107" Big Bore Forged Piston Kit 3.937" Standard Bore - For 07+ HD Twin Cams

For 07+ HD Twin Cams

• Compression Ratio: 10.4:1
• Cylinder Bore Diameter: 4 in
• Engine Type: 4-Stroke
• Items Included: Piston Rings,Wrist Pin
• Performance Part: Yes
• Piston Diameter: 3.937 in
• Type: Piston Kit

These big bore pistons work with the stock 4-3/8" stroke flywheels to convert any 2007+ HD® big twin engine from 96" or 103" to 107" displacement with 10.4:1 compression with stock heads. Stock cylinders may be bored to accommodate larger pistons, but we recommend S&S 3.937" bore cylinders which feature high strength alloyed cast iron liners. Pistons are compatible with stock rods with tapered wristpin ends.

S&S® 3.937" pistons are machined to such close tolerances that it is not necessary to measure the piston. Additionally, the low friction coating on the piston skirt of early production pistons with out micrometer window makes taking measurements very difficult. Therefore, hone cylinders to nominal diameter +/- 0.0001" for correct clearance. Current production pistons have micrometer windows in the coating on the piston skirts that allow accurate measurements to be taken. These pistons may be installed by honing cylinder to nominal diameter +/- 0.0001" or by measuring piston and honing cylinder to achieve .002" - .0025" close clearance for street applications or .0032" - .0045" loose clearance for immediate competition use.