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The LS Next block is the first significant change in the bottom end architecture of the LS engine platform. By eliminating the ''Y-block'' design and utilizing conventional style main caps and oil pans, (stock pans can be used with Moroso oil pan spacers) Dart has addressed the problems resulting from the LS engine's separated crankcase bays. Windage is greatly reduced, resulting in increased power and improved lubrication.

This design change led to several additional improvements. The main webs are significantly stronger because the bay to bay breathing windows are eliminated in Dart's design. Deleting the windows also allows the cylinder barrels to be extended by .3750'' into the crank case, providing greater piston support at the bottom of the stroke. Two standard bore sizes are available, 4.000'' and 4.125''. Maximum bore of 4.220'' for iron and 4.165'' for aluminim, or optional Darton M.I.D. sleeve kit allowing up to 4.220'' bore.

All stock and aftermarket LS components can be utilized. Conventional style 4-bolt steel main caps are used. A 5/8'' thick full deck design is utilized for superior strength, with six head bolts per cylinder to provide secure clamping. Dart's priority main oiling system ensures high rpm reliability and includes provision for oil restrictors in the lifter valley.


  • Dart's LS Next block is cast in the USA with premium cast iron alloy or aluminum
  • Conventional style 4-bolt steel main caps with 7/16'' bolts are used
  • Full main webbing for maximum bottom end strength
  • Cylinder barrels are extended by .3750'' at the bottom, providing greater piston support for all combinations
  • 9.240'' deck height, with options of 9.450'' are available which allows for a possible effective barrel length of 9.825'' deck block
  • Extra thick Siamese cylinder bores allow for larger displacement capacity and a max bore size of at least 4.220''
  • A 5/8'' thick full deck design with a 9.240'' deck height
  • Six head bolts per cylinder provide secure clamping for power adder applications
  • Head bolts are upgraded to 7/16" for increased strength
  • Blind head bolt holes don't go through into the water jacket
  • Provision for oil restrictors in the lifter valley
  • Revised low restriction priority main oiling system
  • Pro-Stock / Pro-Mod big block style stepped main oil galley
  • An external oil filter must be used with stock or aftermarket oil pumps
  • Dual starter mounts
  • The water jacket on the #1 cylinder has been expanded for additional cooling capacity
  • LSX style lifter bosses and dog bone provision are provided
  • 100% Made in the USA!


The LSNext MID block upgrade is designed with one thing in mind - strength!  Where regular aluminum blocks fall short, the LSNext MID block takes the win.  Designed to accomodate the need for ever-increasing power levels and to perform on a prolonged basis is the LSNext MID block's wheelhouse.

• Eliminates block cracking due to cylinder failure
• Wet sleeve (diesel design) for in-field replacement
• Virtually eliminates cylinder distortion due to block flexing and harmonics
• Significant cylinder integrity and strength improvement over dry sleeves

• Superior cylinder sealing with diminished or no pan pressure
• Increased bore size potential at current bore spacing of 4.4 inches
• Superior cooling, especially at upper chamber quench area
• Ducted water flow for all applications in either direction
• Engineered Siamese water cross flow eliminating hot spots
• Design removes deck distortion by seating and anchoring sleeves in compression in the lower block area where the maximum aluminum mass is concentrated
• Increased thermal stability of the power section at all operating temperatures
• Compatible with all currently available head designs
• Will support boost up to 50 PSI without distortion
• Absolute minimal weight increase over stock aluminum block configuration

Also available as a ready to assemble package from Steve Morris Engines with finish honing, with complete or partial rotating assembly, or in assembled short block and long block combinations.

Part #: 672

Price: $5,206.70
Please Call for Availability !
Add Block Completion kit:
MID Sleeve Upgrade - 9.240" Deck Only:
Bore Size:

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