Engines and Components› Engines, Blocks and Components

RHS(Racing Head Service)

LS Aluminum Block - 4.120 Bore 9.240 D/H

$6,575.95

SKU: R02M 54903U

Special Order
Special Order
Ships in 4–6 weeks
Free Shipping over $200
$100 Minimum Order
Non-Returnable Item
INSTALL DIFFICULTY
DIY PRO SHOP

Professional / shop required

Overview

The RHS LS bare race blocks are engineered for high-performance engine builders and racing enthusiasts. Available in standard and tall deck height combinations, these blocks offer maximum clearance for up to a 4.600-inch stroke crankshaft. Their unique design minimizes windage in the rotating assembly, improving engine lubrication at higher RPMs.
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Part #: 54903U

In recent years, LS engine technology has revolutionized the GM performance aftermarket. Gen IV engines have set a new standard for factory horsepower and torque. To meet the growing demand of today s high performance engine builders and racing enthusiasts, engineers at RHSesigned an aluminum LS engine block for radical street and all-out racing applications.

This block has a 9.240 deck height with a 4.125 bore and a 5.87 cylinder sleeve length. Cylinder walls are Siamese cast with press-in cast iron sleeves. 12AN feeds for dry sumps. Aircraft-quality A357-T6 aluminum. 6-Head Bolt Design.

This product may expose you to chemicals known to the State of California to cause cancer, birth defects, or other reproductive harm.

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

BrandRHS(Racing Head Service)
Part NumberR02M 54903U
5,000+ Trusted brands
1M+ Enthusiasts
5M+ Parts sold
(760) 282-4645 hello@motormia.co

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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.

Free shipping over $200 in the continental US. Alaska, Hawaii, U.S. territories (Puerto Rico, U.S. Virgin Islands, Guam, American Samoa, and the Northern Mariana Islands), and international orders carry surcharges — most appear at checkout. Some exceptions (LTL freight, or suppliers who quote freight only after we place the order) won’t. In those cases we’ll reach out with the exact charge before your order moves forward.

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