Manley 290930X SBC Rotating Assembly Stroke Bore X-Series Bearings - 383 3.750 4.030

The Manley 290930X is a complete Small Block Chevy 383 cubic inch rotating assembly built around a 3.750" stroke and 4.030" bore (0.030" over). The "X" suffix denotes the inclusion of Manley's optional "X" Series rod bearings with .001" extra clearance, making this kit ideal for engine builds requiring slightly looser bearing tolerances for high-performance or forced-induction applications.

At the heart of this assembly is a lightweight 4340 forged steel crankshaft that has been heat treated, stress relieved, shot peened, nitrided, and 100% magnafluxed for maximum strength and reliability. It is paired with 4340 forged steel H-Beam connecting rods featuring 7/16" ARP cap screws, and 2618 forged aluminum Platinum Series pistons with premium chrome moly wrist pins.

Kit Contents:

• Lightweight 4340 forged steel non-twist crankshaft — 3.750" stroke, 350 main journals
• 4340 forged steel H-Beam connecting rods — 6.000" center-to-center length with 7/16" ARP cap screws
• 2618 forged aluminum Platinum Series pistons — 4.030" bore (0.030" over)
• Premium chrome moly wrist pins
• High-performance piston rings (Classic Race conventional style with plasma moly top rings)
• Clevite "H" Series narrowed rod bearings — X variant with .001" extra clearance
• Clevite "P" or "H" Series main bearings

Key Features:

• Crankshaft is heat treated, stress relieved, shot peened, nitrided, and 100% magnafluxed
• Micro-polished large-radius journals for reduced friction and extended bearing life
• 2618 aluminum piston alloy offers superior strength for boosted and high-rpm applications
• Horsepower capability rated up to 750 hp with standard ARP 8740 cap screws (upgrade to ARP 2000 for up to 1,500 hp)
• Note: This rotating assembly is unbalanced — professional balancing is required before installation

The Manley 290930X delivers a premium foundation for a high-performance 383 small block Chevy build, combining race-proven components with precise manufacturing tolerances. Balancing service (Manley P/N 04000-1) is available separately and is required prior to engine assembly.