Chevrolet Performance LSX Semi Finished Standard Deck Bare Block

LSX Bowtie Block Standard Deck



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LSX Bowtie Block

The next generation of high performance GM blocks has been released! It’s the amazing LSX bowtie block, designed from the ground up to deliver maximum value while providing you with the foundation to build the LS engine of your dreams.

GM Performance parts, working with NHRA pro stock legend Warren Johnson, designed the LSX block to be the ultimate high performance LS block. Our goal was to bring the LS community race block technology at street car prices. Just like every engine part in the GM performance parts portfolio, the LSX Bowtie block is held to the highest industry standards for tolerances, materials and construction.

We think that you’ll find the LSX to be the ultimate in high performance LS engine blocks!


  • 100% CNC machined cast iron
  • True priority main oiling
  • 6 head bolts per cylinder
  • Standard 4.400″ bore spacing
  • Extra thick siamese cylinder bores
  • Fully machined bores, ready to hone to fit
  • Semi-finished, machined decks, ready to be decked to your specs.
  • Increased deck thickness
  • LS7 style 6 bolt “dowel located” main bearing caps
  • Wet sump and dry sump cabability
  • Deep skirted head bolt holes (same as OEM aluminum blocks)
  • All stock bolt holes are stock thread size
  • Maintains all OEM “LS” family exterior mounting features
  • Front motor plate mounting holes added
  • Added material around cam bearings for extra strength
  • 8mm exterior/interior 5th and 6th head bolt holes
  • All 5 cam bores machined for bearing # 12453169
  • Standard .842″ lifter bores
  • Screw-in soft plugs
  • Accomodated any “LS” series oil pand and oil pump
  • External oil pump feed at rear of block
  • Main web bay to bay breathing holes for increased HP
  • Access windows for cylinder head stud access (intake side)
  • Extra breathing pocket added near starter for better windage
  • Includes new cam retainer # 19166177, rear cover #19166178, lifter retainers #19166182 and OEM replacement cam bearings


  • 3.880″ finished siamese bores (ready to be honed to your specifications)
  • 9.26″ semi-finished standard deck height (ready to be decked to your specifications)
  • Max. 4.250″ reccomended stroke
  • Capable of 364 to 482 + C.I.D.
  • Orange powder coat finish
  • Accepts all Gen III & IV LS heads, cranks, cams etc.
  • Approximate finished weight – 225 Lbs

Engine Builder Features:

  • Front oil feed holes can be plugged or restricted for mechanical flat tappet or mechanical roller lifter cam applications
  • Can be safely machined to 9.20″ deck height
  • main bearing cap bolt threads can be machined for aftermarket 12mm fasteners
  • Maximum 4.250″ bore (at .200″ wall thickness)
  • 6-bolt head bolt pattern (for boosted applications)
  • Machined for 8mm inner and outer 5th and 6th head bolts
  • Standard bolt holes can be machined for larger diameter lifters and/or bronze bushings
  • Front oil feed lines can be plugged and external oil pump and/or aftermarket dry sump oil systems can be used via oil pump feed at rear of block – may be required with certain long stroke & aluminum rod combinations
  • Belt cam drive systems can be accomodated (some machining will be required)
  • External oil pump feed at rear of block
  • 7th transmission bolt has been added (per early SBC) stud can be installed for sanctioning body requirements
  • Front motor plate can be used for racing chassis applications
  • Threaded water plugs can be used for external heaters or coolers


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