We're looking into developing some new products for the LSX engines, and we will be introducing a new LT1 cylinder head very soon. So now you have the scoop on that!
Aluminum Blocks
Dart doesn't always recommend using alluminum blocks in street applications. "Other than bragging rights, saving weight is really the only reason to use an aluminum block," says Jack. "In a street car, there won't be any power difference from iron to aluminum blocks, but in very high-horsepower situations, the iron block will actually make more power because of its superior ring seal." Another consideration is the difference in expansion rate between iron and aluminum. "With an aluminum block, it is more important to let the motor come up to temperature before any hard use and to check the fasteners more often because of the greater expansion rate of aluminum."
Aftermarket Block Design
"Factory blocks are designed to be produced inexpensively and perform up to passenger-car expectations. Aftermarket blocks are designed for racing and performance use. Essentially, they are stronger and offer the engine builder more options. Dart uses higher-grade alloys, which contribute to greater strength. The castings are designed with thicker cylinder walls, which allow larger bore sizes while maintaining better ring seal. Deck thickness is also increased, and various deck heights are available to allow more flexibility in designing combinations. Likewise, the main caps are beefier and made of better material than stock. Aftermarket blocks have a superior oiling system, delivering oil to the main bearings first, then the cam and lifters. By relieving much of the restriction in the oil passages, we can eliminate the need for a high-volume oil pump. Furthermore, water jackets are enlarged to enhance cooling, and the head-bolt holes are blind, which keeps them out of the water jackets."
Using compacted graphite in an iron block doubles its strength without increasing weight. This is a good option for high-boost forced induction or nitrous applications.
Manifold Design
For optimum performance, the intake manifold and the intake port of the head should be viewed as a single package. The manifold's runner volume, runner shape, and plenum volume need to be designed around the heads. If the manifold is too big or too small then performance will suffer. "We do the initial designs based on our collective knowledge and refine them using wet-flow testing, dyno time, and on-track testing," explains Jack. Consequently, Dart manifolds are designed to work specifically with Dart heads. "Rather than trying to make a universal manifold, we generally design an intake manifold for a specific head and type of use. This doesn't mean our manifolds won't work with stock heads or a different brand of heads, it just means they are optimized for Dart heads."