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DRT31837211 - Dart 4.125" Bore LS Next Engine Block

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Dart’s LS Next block is the first significant change in the architecture of the LS engine platform. By eliminating the “Y-block” design and utilizing conventional style main caps and oil pans, Dart has addressed the problems resulting from the LS engine’s separated crankcase bays. Windage is greatly reduced, resulting in increased power along with a much stronger main web area.


  • Dart’s LS Next block is cast in the USA with premium cast iron alloy
  • 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 .375” at the bottom, pviding 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 large displacement capacity, and a max bore size of at least 4.200”
  • 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
  • Dart’s new LS Next iron cylinder block is one step closer to hitting the market following a series of oil-system tests. The block was first shown at the SEMA show last November, and it’s designed to take advantage of the LS engine’s positive attributes while removing the negatives from the equation. Basically, the new block supports LS cylinder heads and other major components but replaces the troublesome Y-block side skirts with Gen I-style main caps and oil-pan rails. The result is less crank windage and stronger main web.

    The oiling system was the most critical issue that company founder Richard Maskin and his team tackled during the block’s development. The first test used an external pump and a modified Moroso Rocket-block pan core. The second test utilized a stock LS oil pump, which was modified with a weaker pressure spring, and a Moroso LS oil pan with pan rail spacers to make up the difference in the skirt length. These adjustments maintained the oil desired oil pressure in the engine without the excessive volume that the LS often requires. “According to my sources, the stock LS7 uses somewhere around 18 gallons per minute revved up, while our design uses much less and still provides more-than-adequate oiling across the board,” explains Maskin. “So far, we’ve created two blocks – the first one was cut up for inspection, and the block used for this test was number two. Now that the initial testing has been run, we plan to pour 25 production blocks next week, which will be available for purchase on or about the first of May. “We’ve got two more tests to run,” continues Maskin. “The first being a Pro Stock dry-sump system with 25 inches or more of vacuum to see what power potential is really in the oiling system. For the second test, we’ll be going back to the stock pump with an all-out, baffled, screened, wet-sump oil pan.”

    More power than expected

    The test engine was fitted with Dart’s CNC-machined LS1 heads, a “reasonably small” solid-roller cam, GM intake and 850cfm carb. “As far as performance goes, there are plenty of performance parts out there – heads, manifolds, etc. that are much better than what we used in this engine,” says Maskin. “We were just trying to prove that the block worked as it was designed to work.”

    Experts at Lingenfelter Performance and Nickens Racing Engines had earlier suggested to Maskin that the engine with those parts would make about 640 to 660 horsepower. As indicated by the dyno results below, the engine hit a peak of 740 horsepower and averaged 701 horsepower from 5,600 to 8,000 rpm.

    Click On Documents Tab to view Dyno results

    Dart’s new LS Next block features 4-bolt steel main caps with 7/16-inch bolts and full main webbing for maximum bottom-end strength. The cylinder barrels are .375-inch longer for better piston support and ring seal. It comes with a 9.240-inch deck height and 5/8-inch deck thickness. The siamesed cylinder bores can be opened up to 4.200 inches, allowing for large-displacement options. The block also features blind head bolts: four 7/16-inch head bolts, one 3/8-inch and one stock-sized inner hole per cylinder to improve clamp force in power-adder applications. There are provisions for oil restrictors in the lifter valley to complement the low-volume, priority main oiling system. LSX-style lifter bosses and dog-bone provisions are also included with the LS Next block – it will easily accommodate 1.060-inch bushings with .937-inch lifters. The block also features a Pro Stock/Pro Mod-type big-block style stepped main oil galley. Lastly, the water jacket around the No. 1 cylinder has been expanded as well as around the outside of each cylinder barrel for additional cooling capacity.

    Application List



    • 31837211
    • 31837211
    • Dart
    • Special Order Item
    • New

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    • 500.0 lbs.
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