What is the horsepower rating for this rotating assembly?

With the standard 7/16" ARP 8740 cap screws on the connecting rods, this assembly is rated for up to 900 horsepower. Upgrading to optional ARP 2000 cap screws increases the rating to 1,500 horsepower.

What materials are the crankshaft, connecting rods, and pistons made from?

The crankshaft is made from 4340 forged steel. The connecting rods are also 4340 forged steel H-beams, and the pistons are forged 2618 aluminum from Manley's Platinum Series.

Can this rotating assembly be shipped to California?

No, this rotating assembly is not CARB approved and cannot be shipped to California due to emissions regulations.

Specifications

Brand: Manley Performance
Part #: 29555HX
UPC: 807298087412

Manley Rotating Assembly, BBC 555 4.250 STROKE/4.560/+43cc

Name: Manley Rotating Assembly, BBC 555 4.250 STROKE/4.560/+43cc
Brand: Manley Performance
SKU: manley-performance-manley-rotating-assembly-bbc-555-4-250-stroke-4-560-43cc-t14-880921
Price: 4083.56 USD
Availability: BackOrder

$4083.56

On Backorder

Order now to reserve yours — we'll ship as soon as stock arrives. Full refund if we're unable to fulfill.

Manley BBC 555 rotating assembly, 4.250" stroke. Built for high horsepower applications.

Key Features

Fits Big Block Chevrolet (BBC) engines.
Features a 4.250 inch stroke crankshaft.
Includes 4340 forged steel H-beam connecting rods.
Comes with 2618 forged aluminum Platinum Series pistons.
Standard configuration supports up to 900 horsepower with ARP 8740 bolts.
Optional ARP 2000 cap screws allow for up to 1,500 horsepower.

This rotating assembly is designed for Big Block Chevrolet (BBC) engines. Please verify compatibility with your specific engine block and build specifications.

⚠️ CA WARNING: This product can expose you to chemicals known to the State of California to cause cancer and/or birth defects or other reproductive harm. Learn more

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About this part

Product Details

If you're building a serious big-block Chevrolet (BBC) engine, this Manley rotating assembly is a solid foundation. This kit is designed for a 555 cubic inch displacement, featuring a 4.250-inch stroke crankshaft and pistons with a 43cc chamber volume. It's a well-built package aimed at serious performance builds where strength and reliability are paramount.

At the heart of this assembly is a 4340 forged steel crankshaft, chosen for its inherent strength and ability to handle significant stress. Paired with this are 4340 forged steel H-beam connecting rods. These rods come standard with 7/16-inch ARP 8740 cap screws, a popular choice for many performance applications. For those pushing the limits, there's an option to upgrade to ARP 2000 cap screws, which significantly increases the horsepower handling capability of the assembly.

The pistons are forged from 2618 aluminum, part of Manley's Platinum Series, and include premium chrome moly wrist pins. This combination of materials and design means the pistons are lightweight yet strong enough for high-RPM operation and significant cylinder pressures. With the standard ARP 8740 bolts, this assembly is rated for up to 900 horsepower. Opting for the ARP 2000 bolts raises that ceiling to an impressive 1,500 horsepower, making this a versatile choice for a wide range of powerful BBC builds. Please note this assembly is not CARB approved and cannot ship to California.