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Home 2013 Editions April, 2013

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Most engine builders worth their salt know that with the components and technology available today, it’s not that difficult of a task to make horsepower. With the availability of so many performance parts – whether it’s from the OEM or the aftermarket – engine builders can pull from vast resources to achieve a balance between reliability and horsepower.

Reliable and enjoyable horsepower can be made so easily today that I often think about what it was like, say, ten years ago when it was such a struggle, and an expense to “go-fast.”

With that thought in mind, I sometimes ponder the changes that have taken place in the manufacturing world that put us where we are today. It is not so much as the hard parts such as cranks, blocks, connecting rods and cylinder heads, as much as the different alloys that are being used to manufacture these hard parts, which, subsequently, make power also.

Take cylinder heads, for instance. What changes can possibly be made to them that have not been accomplished already? Yes, the goal is airflow, but high cfm numbers don’t seem so unrealistic anymore. In today’s performance market there is a cylinder head for practically any street application or racing class you can imagine.

There are also CNC programs that are offered by aftermarket companies that can port a cylinder head for, as an example, a late model Hemi. So, airflow through the cylinder head is not really the hurdle it used to be. The challenge now is the valvetrain.

The weight of the valvetrain seems to be where the focus is at the moment. Trying to reduce the mass of the valvetrain while increasing opening and closing rates of the camshaft and trying to keep the valve from bouncing on the seat is not just a hurdle for engine builders and racers, but for the manufacturers as well.

Production engines now make more power than ever while offering considerable fuel mileage with longevity. With this in mind, we can see what materials the manufacturer (as well as the aftermarket suppliers) are using to keep up with today’s valvetrain technology.

Valve Seats

First of all, we’ll discuss valve seats and what’s going on with the changes that are taking place. What is the importance of the valve seat? Let’s think about its job first. The seat has to seal against the valve face in order to achieve the necessary efficiency in the engine. Second, the valve seat has to transfer heat from the valve face. For quite some time now, more than 90 percent of OE applications have used what is known as a powdered metal (PM) valve seat.

PM offers great durability and is a lot less expensive to produce. The great thing about powdered metal is its ability to retain its shape to ensure valve seal along with the ability to remove heat. This comes from how the seat is produced. The process that is used to form the powdered metal seat allows the materials that make up the PM seat to become more uniform. The old process of making a cast seat presented several problems.

According to Chuck Barnett at Dura-Bond Bearings, “When you pour a cast seat, you pour it hot. When poured in liquid form, you get voids from gases plus hard spots.”

Barnett says that cast seats often resulted in uneven mixing of materials and the seat was often not uniform, which made them more difficult to machine. When making a PM seat it’s like baking a cake. All the ingredients are added together and mixed cold. Then the mixture is placed in a press and squeezed by 100 tons of pressure. The rate of 200,000 pounds per square inch makes the material more consistent.

There are different blends of materials that are used to make different types of PM valve seats. Sometimes “softer” blends are created for use in some racing applications to lower valve bounce at higher rpm. This also gives the opportunity to incorporate other materials into the mix when making the powdered metal valve seat such as graphite, which will offer some lubrication.

Dura-Bond also offers a new line of PM seats they call the “Killer Bee” series. This series of valve seats is based on a copper infiltrated design used by GM in the LS3 V8 engine. The process of making this seat is the same as others where the mixture is pressed together. But now a copper wafer is added to the top of the mixture and then sent through a furnace where the copper melts into the mixture.

The molten copper penetrates the seat that results in a 15% copper mixture which offers a 4-6% faster heat transfer from the valves to the head. The Killer Bee has excellent machining capabilities along with reduced wear and superior finish. The Killer Bee series can be used with steel valves only because of the carbide hard phase process. And Titanium valves can be used, but only if they are coated.

Speaking of titanium valves, another choice of seat would be Beryllium copper. This material is noted for high strength and thermal conductivity. The greatest asset would be the ability to remove heat from the valve while taking a beating. Beryllium is only used in extreme racing applications. This is due primarily to the expense: a seat can cost an average of $35 each.

The biggest problem with Beryllium copper is the machining process. Here in the U.S., OSHA limits the amount of time someone is exposed to the material while machining in a controlled environment. When machining, small dust particles are released into the air that when inhaled over a period of time can cause severe lung damage and even death. So, it’s not just the price of the seat but also the price of machining the seat. Ductile iron is also a less expensive choice when using titanium because of its strength and durability.

One thing new for Beryllium copper has been developed by Exceldyne. They have recently developed a proprietary valve seat finish. This new technique improves the Ra of the valve seat while still maintaining the sharp edges that contribute to airflow. This form of finishing technique also promotes coating adhesion, which can now be used to reduce the wear on the copper based valve seat.

When rebuilding cylinder heads, one choice is the use of a high chrome valve seat. These seats work well when repairing OEM cylinder heads. They offer great strength and dependability while being very cost effective. They are easy to machine and offer great longevity when used for applications such as daily driving.

Tungsten carbide is used primarily for diesel applications. The cool thing about tungsten carbide is the more the valve seat is pounded the harder it gets. This is crucial to the life expectancy of the diesel engine. This helps these engines operate close to a million miles or more for over-the-road trucks before a rebuild.

Tungsten carbide is inexpensive to machine and produce, making it very cost effective as well. Dura-Bond manufactures a tungsten carbide seat with special additives that offer high temperature lubricating properties, which is not affected by high heat or machining.

These seats also work well in dry fuel applications such as propane and natural gas. High nickel has been used in propane and natural gas applications with great success. Since there have been more advances made for the use of diesel, propane, and natural gas, valve seat material has to be similar to ceramic in which the seat does not soften at elevated temperatures along with the ability to be machined like metal.

Valve Guides

Valve guides can be generally classified into two groups: cast iron and manganese bronze, which covers a wide range of applications.

Cast iron guides are used mostly by OEMs due to its wear characteristics that result in longevity for high mileage applications. Cast iron is used with chrome valve stem applications as well. Cast iron cannot be used with stainless steel because of its tendency to gall.

That’s why high performance applications do not warrant the use of cast guides due to the fact the material can’t handle the high loads associated with higher spring pressures. Under high stress, cast iron guides tend to crack and fracture, which can result in engine failure altogether. Cast iron is inexpensive and works best with daily drivers and high mileage applications.

For any kind of performance application, the choice is manganese bronze. The way to pronounce this correctly is MAN-GA-NESE. I often hear this as magnesium, which is not correct. Manganese bronze is ideal for performance because it is more compatible with titanium and stainless steel.

It has the ability to handle high stress loads with some lubricity, and the ability to have tighter tolerances with great heat transfer. Manganese bronze works great with higher valvetrain speeds and offers great corrosion resistance. The material make up of manganese-bronze guides generally consists of 55% copper, 40% zinc and 3.5% manganese.

As far as any other materials used in performance, manganese-bronze is still the best choice for valve guides. One thing that has evolved with the material is the way that it is being machined today. Precision Engine Parts (PEP) now offers their manganese-bronze guides with an internal groove.

This internal groove provides the intrusion of a small amount of oil into the guide area for added lubrication. This is used mainly in endurance applications. This high-quality material is manufactured in Germany and machined here in the U.S. by PEP.

Another added feature to manganese bronze guide was introduced by C.H.E. Precision Machine. C.H.E. integrates an internal O-ring into the guide instead of using an external valve guide seal. This was done because of the increased valve lifts in performance.

Valve lifts as high as .900? are becoming common in class racing. This style of guide with an external O-ring is beneficial because of the time it takes to reach these kind of valve lifts where triple valve springs must be used, which limits room for the valve stem seal. By being able to remove the seal, more length can be added to the guide allowing more stability in the valvetrain.

One more new thing to the market is the introduction of the high-temperature copper-bronze valve guide by Ferrea Valves. This is a proprietary heat treatment of the copper-bronze alloy that so far has better heat-resistance, lubricity, and the material has the ability to increase the heat-dissipation.

These copper-bronze valve guides are CNC machined and concentrically ground, which allows the tolerance range to be taken within .0005?. These valve guides are now being offered for domestic, import, and motorcycle applications.

Like I mentioned earlier, the primary focus of making power is to reduce the mass of the valvetrain. The reduction in valvetrain weight seems to be making big gains in finding more horsepower. This practice is becoming more common from racers to professional engine builders, to the OEM and aftermarket manufacturers.

For suppliers of valve seats and guides, visit our online buyers guide. Special thanks to the following for their input: PEP Precision Engine Parts, Dura-Bond Bearings and Ferrea Valves.

 

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Bob McDonald

Bob McDonald

Owner at Atlantic Engines
Bob McDonald is owner of Atlantic Engines in Granite Falls, NC, and specializes in high performance diesel and gasoline engines and cylinder heads for street, marine, dirt and drag racing.