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RHS 54906U LS Aluminum Race Block, 9.240 Standard Deck - 3.895 Bore
RHS 54906U LS Aluminum Race Block, 9.240 Standard Deck - 3.895 Bore

RHS 54906U LS Aluminum Race Block, 9.240 Standard Deck - 3.895 Bore

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RHS 54906U LS Aluminum Race Block, 9.240 Standard Deck - 3.895 Bore
RHS 54906U LS Aluminum Race Block, 9.240 Standard Deck - 3.895 Bore
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We estimate this item will ship on or before December 18th.
Part # 59054906U
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  • This item ships directly from the manufacturer. It may take an additional 2 business days for Racing Head Service to ship this item.
  • This item ships via Ground Shipping only. Expedited and Air shipping options are not available.


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  • Standard Deck Height (9.240)
  • Needs Final Finish Hone Before Assembly
  • 5.87" Cylinder Sleeve Length
  • 3.895" Bore

Engineers at RHS have designed a high performance aluminum engine block for GM LS applications to meet the needs of race and street performance engine builders alike. To go beyond the limitations of other existing LS blocks, the new RHS LS Race Block is available in both standard deck and tall deck height configurations. Additionally, this innovative aluminum block features a raised cam centerline and outboard priority main oiling to allow rod clearance for a 4.600 stroke and to minimize windage in the crankcase. And for quality control assurance, RHS conducts a CT scan (similar to a medical CAT scan) on each block to ensure maximum casting precision and consistency. When you combine unmatched finishing quality with added clearance for increased stroke applications, precision computeraided design and extra surface material to allow custom machining, you get the new benchmark for LS horsepower, torque and durability.

  • Designed from heavy-duty A357-T6 aluminum material
  • 4.125-4.165 siamese cast bore walls w/ press-in spun cast iron liner

  • Available in standard (9.240) & tall (9.750) deck heights w/ beefy .750 deck thickness

  • Both standard deck (5.67/5.87- same as LS7) & tall deck (5.94/6.38) cylinder liner lengths available

  • Long arm friendly Accommodations for up to 4.6 stroke w/ standard rod pin diameters (2.100) & oversized 60mm camshaft

  • Raised cam centerline (.388/9.86mm) to allow larger stroke; 2 extra links in the timing chain Timing sets available from COMP

  • Main cap surface area maximized at mating surface & large fillets from cap to cross bolts for added strength

  • Designed for clearance side oil galley moved outboard & engineered rod clearance come standard

  • Significantly increased windage passage area under bores & around caps over LS7/LSX engines

  • 6 head bolt design w/ full water jacket around the cylinders (based on LS7 design)

  • Bay-to-bay breathing improved w/ increased side window area versus LSX & LS7

  • Extra large windows in valley for access to inboard 6th head bolt

  • Extra long liners for standard (5.87) & tall (6.38) decks

  • Provisions for Gen III & Gen IV cam & knock sensors & valley covers

  • Cam tunnel will accommodate stock through oversized 60mm roller bearing cams (includes cast-in lock screw pads)

  • .842 lifters standard with material available for oversized lifter access (accepts 1.060 bushing for keyed lifters)

  • In the standard deck, maximum pushrod angularity = Less than 2 degrees

  • Includes Ampco 45 cam thrust plate and aluminum rear cover

  • Lifter bosses designed to clear tie bar lifter

  • Priority main oiling, galley moved outboard for long stroke clearance

  • Oil filter feed galley GM dog bone replaced with proprietary no restriction threaded plugs

  • Dry sump friendly with provisions for more serious dry sump setups; includes big front & rear AN-12 side feeds

  • Includes provision for piston oil squirters, cast-in & machined

  • Rolled threads on all threaded holes for added strength

  • Gen III/Gen IV compliant with race mounts for Gen I, Gen II, Gen III & Gen IV engines

  • ARP main stud kit standard with enough material in castings to accommodate up to a ½ fastener

  • Chilled main bearing bulkheads for added strength

  • Optimized billet main caps & improved windage

Some parts are not legal for use in California or other states with similar laws/regulations

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