When it comes to circle track-ready blocks, DART’s billet components provide an excellent platform.

The term gets bandied around a lot. “Billet” components are defined by experts as parts that were created from a single block of material. That is a fact lost in many advertising campaigns that allude to their products being billet quality without actual billet construction – a case of promising a lot without ever really delivering the “goods” in terms of strength and reliability.

Rest assure, that Dart’s billet blocks are just what they promise starting with a 600-lb block of 6061 aircraft grade aluminum whittled into a small block engine form. From the initial shaping, the material is then heat treated to penetrate the surface of the material making it strong and yet retaining the lightweight features. It is then final machined to the owner’s requirements from there by the engine builder. These blocks avoid the porosity problems found with cast blocks where small gas bubbles are emitted during the curing process creating a less dense component and other inherent problems not found with billet construction.

So why would circle track racers require such a high tech piece when there are so many quality cast aluminum components on the market? Simple. With most late model racing applications, the block is actually part of the chassis, an integral part of the entire vehicle and one of the weak links for many when racing. Simply put, cast blocks are often not up to the task. Just ask Jack Cornett of Cornett Racing Engines in Somerset, Kentucky – engine builder to the current top two racers in World of Outlaws late model dirt competition, Josh Richards and Darrell Lannigan.

States Cornett, “ With the cast blocks we were experiencing a lot of cracking of these engines especially in the motor mount area. These engines see a lot of stress and the cast blocks just can’t handle it. You are not going to break or crack one of these billet aluminum blocks.”

In addition to the benefits of the tougher block construction, Dart set about creating a block in a spread bore configuration – spreading out the bore centers to provide even greater strength and ultimately better breathing with these state-of-the art components. In essence, the bore centers on the Dart billet small block Chevy engine are moved from 4.400-inch to 4.500-inch – that’s a big deal. When tandemed with Dart’s 9-degree valve angle cylinder head, you have the best of all worlds.

“In the high end late model racing arena, the spread bore racing engines have become the norm for a lot of reasons but especially because it allows engine builders to generate a lot more power and increase bore sizing,” states Jack McInnis, VP of Marketing for Dart. “When you are talking about building a 430cid small block Chevy engine for racing you want to be able to increase the bore size rather than increasing stroke. With the spread bore spacing it also allows you to get a better head gasket seal between bores that that is critical with these engines.”

To meet the new billet block cylinder spacing, a new cylinder was required. To that end, Dart looked for ways to improve breathing and determined that a 9-degree valve angle would provide a much straighter, raised fl oor, better fl owing port design (standard small block Chevy valve angle is 23-degrees). Big block style canted valve heads for the small block have replaced the standard in-line cylinder head in NASCAR due to their increased performance. The new 9 degree Dart head offers performance comparable to splayed valve heads but maintains the ease of use associated with in-line valve heads.

Notes McInnis about the Dart billet block, “with a casting, no matter how careful you are there is always some core shift and internal porosity from expanding gas from the process – it is just inherent. With billet blocks you get the most strength working with an extremely dense single piece of material. Best of all you don’t have to compromise as these blocks are infinitely customizable with full or half water-jacketing, camshaft and lifter placement, etc. You are really only limited by the components you can come up with to bolt on to it.” For Jack Cornett, the benefits of the Dart spread bore billet blocks are greatly appreciated and have netted some impressive results. Concludes Cornett, “we dyno test all of our engines to ensure they perform as promised. They have all run extremely well.”

Source

Dart Machine

www.dartheads.com

248-362-1188