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How Much Extra Can High-Performance Valves Give?

Performance engine builders can choose from many intake and exhaust valves to choose from. With the variety of surfaces and materials available, it is necessary to conduct an extensive amount of research to choose the best valves to fit the purpose and application usage.

In the world of serious performance the intake and exhaust valves are more complex than what’s apparent. Because of the advancements in technology made in the race components industry, we now have an overwhelming array of options. The article below will will attempt to provide a detailed explanation of the various designs and materials to help the current offerings of valves.

Stainless-Steel Valves. Although stainless-steel-based valves are available in various quality and alloy recipes High-performance stainless-steel valves are usually constructed from a material known as EV8 (a higher-priced heavy-duty stainless alloy) They are made by forging a single piece. Additionally, certain valve makers provide a stronger stainless-steel blend that provides greater resistance to heat. Certain manufacturers use EV8 exclusively in their exhaust valves however, others use it to make both intake and exhaust valves.

Premium performance stainless GSC racing valves should include stellite tips made of hard material (since stainless isn’t able to be hardened and a tip that is hardened must be welded to the stem) and stems with hard chrome plating (not flash chroming that is cheap) to decrease wear on guides. Stems cut undercut help in a slight weight reduction and improve the flow characteristics. Be aware that if a specific type of stainless-steel valve does not come with a hard-tip using caps that lash are needed.

Titanium Valves. Titanium is the strongest metal with the greatest strength-to-weight ratio among all known metal. In a non-alloyed state titanium is as durable as steel, but around 45 percent lighter. When it is used in the manufacture of automobile valves, it is alloyed with tiny amounts of different materials, such as molybdenum and copper. Titanium is a difficult material to work with, since it may swell if the tools aren’t sharp and hard enough, or when the material isn’t cool appropriately during processing.

The majority of titanium valves are manufactured through forging, which is then machined into a the final form. Some are manufactured by using a two-piece design that is inertia-welded. Based on Xceldyne Technologies, this process is so efficient that inertia-welded valves have been recognized to have a higher grain structure over a single-piece made design. The valve is CNC-machined, and often subcut in the stem to create a bed to allow for the inlay of a coating. After that, the valve gets moly-coated.

The valve’s specific sections are then machined further and the stem is then ground, leaving the moly-based plasma coating just over the area of the stem that is desired. The stem, head and keeper grooves then final-machined. The stem grinding process is completed to ensure dimensional accuracy of.0002 in .0002 in. The final polishing reduces the risk of carbon accumulation.

Three different types tip styles for valves are available, and include the hardened steel tip, or a tip coated with ceramic (ceramic tips are utilized together with caps for lash) and thin-film technology , such as plasma vapour deposition (PVD) coating.

Since titanium is a soft substance, it demands an appropriate contact surface near the tips of the stem, which is usually the lash caps are made of hardened. Xceldyne observed that when valves have stem diameters of less than 5/16 inches. (7mm and smaller), a special hard coating is placed on the stem’s end to guard it against the friction of the lash cap.

The tough, hard ceramic coating is designed to protect the titanium from friction created by the cap’s lash. Other coatings like PVD treatment, Chromium Nitride treatment Chemical liquid deposition (CVD) diamond-like carbon (DLC) or any other specific protective applications can be placed on the tip. The hardened area at the tip stops the transfer of material or galling from the tips to the cap.

The hollow titanium valves are offered with hollow stems or hollow heads and hollow stems. Hollow stem designs decrease the weight of valves by approximately 10 percent. This design uses an exclusive method that helps remove an additional 6-8 pounds of mass (depending on the size of the valve). As part of the exclusive procedure, the inside part of the head can be reinforced to create an additional support structure to ensure durability and strength.

The following precautions must be observed during handling and usage for titanium valves

Don’t use your hands alone, as fingerprint acids can alter the coating. Wear gloves or cover the valve with oil prior to handling.

*Do not use lapping compounds or any other abrasive materials when you are coating the valve with PVD.

*Replace the valve seats after any rebuild, to assure correct valve-to-seat fit. The distance between the Contact zone (valve face to seat) must be at least 1 millimeter.

*New valve seats must be relatively soft materials like nodular iron or bronze (heat-treated up to Rockwell RC32 (or less).

Unless otherwise instructed by the valve manufacturer, always use lash caps that are hardened for titanium valves. Certain valve makers make valves with tips made of friction-welded steel. Titanium tips that are unprotected will swell when exposed the forces of a rocker arm.

In the event that the valve has an stellite tip The tips may be ground during valve maintenance However, it is important to be careful. It is recommended to remove safely a maximum of .015 up to .020 in.

When it comes to seat valves are involved traditional hard or cast seats can create grooves in the valve face, therefore the use of a nickel-bronze material for seats is suggested. There are other exotic metal seats available.

Titanium valves are specifically designed to be used in situations where the weight of the valve train must be decreased, especially for extended high-rpm and applications with high rpm, as titanium valves can accommodate greater engine speeds and can be able to handle extremely aggressive camshaft profile. However, in extreme temperature situations (blown or turbo engines) titanium may not be the right option. Additionally, for a lot of applications on the street, titanium might not be the best option for engines that don’t require to rev as much or which is buttoned up and not torn and maintained frequently. It’s recommended to restrict titanium for naturally aspirated race, or inlet-side forced-induction applications where the weight of the valve train and long-term high-rpm usage is crucial.

Inconel Valves. Inconel is a trademark registered from Special Metals Corp., and is a reference to a variety of superalloys made from nickel. The Inconel alloys can be described as oxidation and corrosion-resistant metals designed to be used in extreme temperatures. Inconel maintains its strength across the entire temperature range. In contrast to steel and aluminum, it does not creep as as (change dimensions) in high heat conditions.

Inconel alloy makeup may include manganese, carbon, silicon and sulfur, phosphorous, nickel cobalt, chromium molybdenum, iron, aluminum titanium, boron, and copper. Copper has the largest amount of material accounted for using nickel and chrome.

5 “grades” that comprise Inconel are commonly used: 600 625, 625 and 690. 718, and 939. In essence, the advantages of Inconel are its light weight and resistant to temperatures that are extreme, superior strength , and resisting thermal dynamics.

Inconel valves have a very strong thermal resistance, and they are specifically designed for high-temperature use, like those they are used in turbocharged Supercharged, Nitrous, and turbocharged.

Nimonic 90 Valves. Nimonic is an alloy of nickel and chrome which is a particular version called Nimonic 90, which is utilized by some manufacturers to create high-performance valves. Nimonic 90 is a superalloy comprised of nickel-chromium-cobalt, which offers high strength and the ability to withstand extremely high temperatures, reportedly well within the 2000degF range, without distortion. Manley has reported that they’ve had great results in applications as extreme as nitromethane as well as high-boost turbo turbo applications like multi-turbo tractor-pull engines.

Sodium-Filled Valves. Sodium-filled valves feature stems that are precision-gun-drilled and filled with a specially formulated sodium. This reduces weight (the result of drilling the gun to create hollow stems) and more efficient heat dispersion. There’s some debate over the effectiveness of this transfer due to fears that heat transfer to guides can cause guide wear. However, even with these issues, it’s important to consider it is that Chevy LS7 engine has salt-loaded exhaust valves (along with intake valves made of titanium).

The hollow spaces between the stem and head of a valve that is sodium-cooled are filled to approximately 60 percent of their volume metallic sodium which melts at around 206 degrees Fahrenheit. The inertia forces created in the process of opening the valve causes the sodium liquid to flow upwards inside the stem, which transfers heat to the guide of the valve and, later, into the valve’s water jacket.

Hollow-Stem Valves. Hollow-stem stainless-steel or titanium valves (no sodium-fill) feature gun-drilling to create hollow stems, strictly for weight reduction–approximately 10% as compared to a comparable solid-stem valve.
General Recommendations

For the majority of street engines using a stainless steel valve, a high-quality one is suggested. Titanium is the most popular choice for race-related applications, however certain engine builders who focus on turbocharged models would prefer an extremely higher-nickel Inconel valve. Hollow-stem valves work well on the intake side however, they are more difficult to make and inspect for any flaws with respect to the I.D. surface. A lot of upper-echelon engine builders are hesitant to use hollow valves because of their potential when it comes to endurance (NASCAR or 24 hour style) racing.

Valve made of stainless steel are used most often in mild-performance racing and street racing. Titanium is employed in situations where weight is a major factor and price is not an important factor. Inconel is a popular choice in situations where exhaust gas temperatures become extremely high. The stainless steel (for street-performance) is much more durable features than titanium. The street racers don’t typically be able to appreciate the advantages of titanium. In racing, utilize titanium if you’re looking to shed weight…and invest a lot of money.

If your client is concerned about durability, concerns and he’s already producing the power you want and is making the engine spin as fast as he’s willing to go, make use of a stainless steel material. If he’s running nitromethane you should consider an Inconel exhaust valve material would be the best option for a successful finish to in a race.

On the other side filling with sodium is the most efficient method to increase capacity for head of the hollow exhaust valve. If steel valves with a diameter of stock are needed, but weight limit is not required switching to an intake that is hollow and a sodium-filled exhaust will definitely be an advantage.

The most important thing is getting the mass out from the valve. The lighter the valveis, the more rigid the valve train system relative to the amount of mass it is required to move. Furthermore, when the mass of the valve is reduced this can decrease the force of the spring needed to regulate a particular valve’s movement and/or switch to an aggressive cam design to generate more power.

Although some valve manufacturers offer solely solid-stem designs, hollow stems definitely provide less mass. It is possible that they are the most efficient way to go however there are important manufacturing and inspection obstacles to overcome when making hollow valves.

The issue for your client is: What is the most secure and efficient method to invest my money to build this engine for this particular project within the budget? The answer may be hollow valves but, generally speaking, it’s likely to be a valve stem that is solid at the very least, unless there is significant technological advancements in the manufacturing aspect. As OEMs are pursuing more innovative techniques for manufacturing valves for the mass market and new technology is developed, it could be available to the aftermarket to manufacture parts for the race and performance side.

The majority of the market is the square groove lock, the stress within the valve are reduced by a only a single circular (radius) groove. The most stress-free system is a top-lock model with a narrow round groove that runs along high-end of lock. The lock is constructed with a smaller pitch than the retainer to ensure that you can hold the valve in place by the collet force, which squeezes more in the bottom of the interface between the valve and lock.

Radiused grooves are designed to address the issue that stress-concentration zones are that are associated with a tiny diameter of an inside of a lock with a square groove. When racing at the highest level, with valves made of any material retainers, locks and other components might only have a single groove, as it causes locks to hold onto the stem of the valve, and hold it in the right position. A lot of OE engines come with multiple grooves of steel valves and locks which allow the valve to spin inside to the lock. This is ideal for street or low-end performance. Since there is a gap between valves and the lock and the valve, it can cause an overstress issue if it’s used in racing with extreme force.