Performance Encyclopedia

Platinum Series Cylinder Heads

The as cast chambers of a Platinum series cylinder head.

The as cast chambers of a Platinum series cylinder head.

The Platinum version of the Dart’s popular Iron Eagle and PRO 1 heads are the direct descendants of Dart’s Pro Stock engine program. wet-flow technology and improved combustion efficiency propelled the project.

“Essentially we’ve revisited and reinvented the standard 23-degree small-block head,” says Dart founder and president Richard Maskin. “There were enough things to change that it justified making a brand-new head from scratch. Our goal was to take advantage of the parts and technology that are now available and bring these heads into the 21st century”.

The cornerstone of the Platinum head project is Dart’s wet-flow bench. This custom-built, computer-controlled [wet-flow bench] fills an entire workroom. Powered by three 50-horsepower electric motors, this amazing machine can flow 800 cubic feet per minute at a vacuum of 55 inches of water. (For comparison, the industry standard for dry-flow testing is 28 inches of water.) A nonflammable liquid with the same specific gravity as gasoline is injected into the intake air stream at a 13:1 air/fuel ratio. This liquid has a fluorescent dye that glows under ultraviolet light, allowing the flow bench operator to visualize the movement of the fuel as it travels through the port, valve and chamber.

“The wet-flow bench was originally intended to be a tool to develop our Pro Stock heads,” said Tony McAfee, who oversees Dart’s cylinder head R&D program. “But when we tested our production heads on the wet-flow bench, it was a revelation. We realized how dramatically we could improve the performance of every Dart head by applying what we’d learned in wet-flow testing.

“If you just look at flow numbers on a dry-flow bench, you’re not going to see a big difference between the original style heads and Platinum Series heads,” said McAfee. “But when you look at the wet-flow, the differences are huge. Fuel distribution around the valve is one of the things we concentrated on, and we did extensive work in the valve bowls and the combustion chambers to improve both fuel flow and air flow.”

The new Platinum heads’ intake seats have five distinct angles – a direct result of Dart’s wet-flow testing. The benefits of a five-angle intake seat don’t become apparent until you test them in a wet-flow condition. Each of the five angles provides a shear point for the fuel to go into suspension before it enters the chamber.

The Platinum Series heads now come with back-cut valves. A back-cut valve makes a big difference in how the fuel is conditioned before it enters the combustion chamber. The end result of all of these changes is that the engine pulls more fuel and makes more power.

The spark plugs in Platinum Series heads are located as close to the top and center of the combustion chambers as possible. This shortens the distance that the flame front must travel and produces a more uniform pressure rise in the cylinder to push the piston downward.

“The original PRO 1 heads were released in 1998, and since then we’ve picked up more than 100 horsepower in our Pro Stock engines,” Maskin noted. “We’re making more power with the same rules, the same engine displacement, and the same valve sizes. Many of the things we have learned in the Pro Stock engine program are applicable to other types of engines and components. That’s why the Platinum Series PRO 1 heads are such an improvement. We work on racing engines every day, and we know that if you’re not moving forward, you’re falling behind.”

Platinum head results are in red, while the older style Dart heads are in blue.

Platinum head results are in red, while the older style Dart heads are in blue.

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