Wiseco 4137FSX Pro Tru Street Forged Flat Top Piston 4.137 in. Bore

The Wiseco 4137FSX is a Pro Tru Street series forged flat top piston designed for small block performance engine builds requiring a 4.137-inch bore. Manufactured from 4032 forged aluminum alloy, this piston delivers a reliable balance of strength, heat resistance, and everyday drivability that street performance enthusiasts demand.

Wiseco's Pro Tru Street pistons are engineered to provide a meaningful boost in horsepower and torque while maintaining compatibility with a wide range of engine configurations. The flat top crown design supports a clean combustion chamber geometry, making it a popular choice for both naturally aspirated and mildly modified street builds.

Key Features:

• 4.137-inch bore diameter — precision-machined to exacting tolerances
• Flat top (F) crown design — optimized combustion chamber compatibility
• Pro Tru Street (S) series — forged from 4032 aluminum alloy for strength and durability
• Single piston (X) — sold individually for custom builds and replacements
• Cam and barrel piston profile for proper piston-to-wall clearance measurement
• Machined valve pockets deeper and larger than stock for improved valve clearance
• Compatible with cast iron, chrome, Nikasil, and boron composite cylinder bores
• Engineered and manufactured in Mentor, Ohio, USA

As with all Wiseco automotive pistons, piston-to-wall clearance should be measured at the widest point of the piston skirt, 90 degrees from the wrist pin hole. Always verify dome-to-head clearance and valve-to-piston clearance prior to final engine assembly.