Dart LS Next Quick Specs
• 9.240in deck height
• Cylinders extended by .375in (effective deck height 9.615in)
• Stock & aftermarket LS components utilized
• Available in standard 4.000in & 4.125in bore sizes (4.200in maximum)
• Manufactured in US using premium cast iron
In Dart’s dyno room on April 4, their new LS Next block was undergoing its final stages of testing before making its production debut. “It produced 740hp @ 7,000rpm,” said its creator Richard Maskin “and it sustained 700hp for a long way.” Configured with 4.155in bore and 4in stroke the 434cu in test engine made 600ft lbs of torque.
Introduced by General Motors in 1997, the purpose of Dart’s LS replacement block is to exploit greater potential from the engine, particularly in the reduction of windage and improved lubrication.
To keep the tests simple and meaningful Dart used a distributor and a carburetor. In so doing they isolated the effects of modern ignition, fuel injection, and electronics from the equation. “It’s got a mechanical roller camshaft in it,” said Richard, “because I wanted to be able to rev it to 8,000rpm with the existing springs. It makes over 690hp @ 8,000rpm. It has a real flat power curve emphasizing its suitability for street use. It’s got a small cam in it, 255/265. It’s got our Cathedral-port heads, GM intake manifold, and a conventional-looking oil pan. It has, however, 12:1 compression ratio.”
To monitor the oil level during testing, a sight gauge was installed on the side of the engine. Because the lubrication system was altered significantly, an external pump was used for ease of adjustability. “When we started out we had too much pressure, so we had to constantly change the bypass spring till we got it functioning within the appropriate range. Now we have the final specification for a stock-style pump.”
Dart felt there was little to be gained by putting an efficient oil pan on the stock block because of its reputation for excessive windage and numerous oil leaks in the crankcase. “You can minimize some of the leaks with lifter bushings in the stock block, but there is still excessive leakage around the main bearings.”
For the new LS Next block, Moroso will produce a full kick-out dry-sump pan, similar to that used in Pro Stock. In the meantime by adapting an existing dry-sump oil pan for testing purposes, Dart charted an engine power increase of 25hp average. Compared with the stock block, which tends to pickup around 10hp, these results were encouraging.
Lastly, Dart’s LS Next block employs 350-style upper main bearing shells, and bearing manufacturer Clevite is currently producing the initial 1,000 sets. Importantly the new bearings accommodate the stock crank. Reassuringly, Dart’s new LS Next block accepts all the stock components including, pistons, front cover, rear cover, cylinder heads, top plate, and so on—everything is designed to accommodate stock LS parts, except the oil pan.