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Engines and Components› Crankshafts and Components

Eagle Specialty Products

Forged 4340 Crankshaft, 4.000-Inch Stroke, 2-Piece Rear Main Seal

$1,238.99 $1,209.99 Save $29.00

SKU: EAG436040006123

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In Stock
Ships by Sep 9
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$100 Minimum Order
30 Days Return
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Overview

The Eagle Specialty Products EAG436040006123 is a forged 4340 steel crankshaft designed for high-performance applications. It features a 4.000-inch stroke and internal balancing, with a 2-piece rear main seal style.

This crankshaft is X-rayed, magnafluxed, and sonic-tested for quality assurance. It includes features such as chamfered oil holes for improved lubrication, a .125-inch radius on rod and main journals for increased strength, and precision-ground, micro-polished journals to less than 5 R.A. A target bob weight of +/- 2 percent is specified to reduce balancing time.
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The Eagle Specialty Products EAG436040006123 is a forged 4340 chromoly steel crankshaft engineered for demanding, high-performance engine builds. This crankshaft is designed with a 4.000-inch stroke and internal balancing, suitable for engines with a 2-piece rear main seal configuration. It is specifically intended for stroker applications and requires machining to the engine block for clearance. Constructed from non-twist forged 4340 steel, this crankshaft undergoes a rigorous multi-stage heat-treatment process, followed by stress-relieving and shot-peening for exceptional durability. Each unit is subjected to X-ray, magnaflux, and sonic testing to ensure top-tier quality and structural integrity. Enhancements include chamfered oil holes for superior lubrication, a .125-inch radius on rod and main journals to bolster strength, and precision-ground, micro-polished journals that achieve a surface finish of less than 5 R.A. The crankshaft also features a tight target bob weight of +/- 2 percent, significantly minimizing balancing labor. Important considerations for installation include the mandatory use of chamfered bearings and the necessity for block machining to accommodate the crankshaft. This component is not intended for use in pollution-controlled vehicles.

Product descriptions are provided by our supplier partners and may not always be perfectly accurate. Not sure this fits? or call (760) 282-4645 and we’ll verify before you order.

Fitment

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Specifications

BrandEagle Specialty Products
Part NumberEAG436040006123
CategoryEngines and Components

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Returns & Fitment

Built for enthusiasts. Every order is backed by our 30 day return window on eligible items. Unused and uninstalled products may be returned with approved RMA and no restocking fees when received in new condition. Orders placed through the MOTORMIA app with a complete build qualify for our Fitment Guarantee — free return shipping if the part doesn’t fit your exact setup. The guarantee covers fit only; installation must follow manufacturer instructions, and we recommend a qualified shop for parts marked Difficulty 4–5.

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Shipping

Orders are processed in 1–3 business days. In stock parts ship promptly from our partner network. Special-order items either aren’t currently stocked or are built to your spec — expect 4–6 weeks. If a part goes on backorder while your order is in the queue, we’ll reach out and work through discounted alternatives together.

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