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RHS LS Race Block 54903

  • Note: Image is a representation of this item. Actual item may vary.
  • Note: Image is a representation of this item. Actual item may vary.
  • Note: Image is a representation of this item. Actual item may vary.
RHS 54903
55.00 KGS
$240.00 (Fixed shipping cost)
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Product Description

Part Number 54903 RHS Block


4.125" BORE


Engineers at RHS® have designed a high performance aluminium 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 aluminium block features a raised cam centreline 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 computer aided 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 aluminium material
  • ·         Main cap surface area maximized at mating surface & large fillets from cap to cross bolts for added strength
  • ·         Designed for clearance – side oil gallery 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
  • ·        


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



*Freight Charge for this item includes insruance.



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