When building a high-performance engine, the details matter. One of the small details that you might not have ever considered is the style of lock groove used in your valve stem. Recently Ferrea Racing Components released a pair of videos detailing the most common types of grooves on the market today, and their individual pros and cons.
The Three Little Grooves
In the first video, Zeke Urrutia, Director of Marketing for Ferrea Racing Components, briefly goes over the three styles of groove. First, there is the “triple-groove” or “three-groove” style of valve which, as the name suggests, has three individual grooves machined into the stem.
“[The three-groove style] is widely used by the OEMs,” Urrutia explains.
“The main function of that style of groove is to allow the valve to physically rotate 360-degrees. That rotation is engineered into the design and allows the valve seat to clean itself of carbon.”
He continues on to explain that the triple-groove is a great design for OEM and high-performance street engines, but that it really isn’t optimal for a race engine. Urrutia also mentions that the triple-groove design, requires three times the machining for each valve, so there is an associated cost increase for that design.
“For a race engine to avoid excessive amount of wear in the groove area, you need the least amount of rotational movement,” he says.
Round is a Shape
The second style discussed is one referred to as a “bead-style” or “radial-style” groove. As the photos show, it is a single groove, which has a completely radiused inner groove.
“The radial-style groove is commonly used in race applications. It is also used in both stainless and titanium valves, as well as in hollow-stem designs. It’s actually very popular in titanium valves,” Urrutia says.
“The radial-style groove works really well, because the rounded edge of the top part of the groove cushions against the lock. If it ever gets into uncontrolled and/or excessive valve movement, the radius cushions any impacts.”
In addition to preventing damage should the worst happen, it also offers approximately 30-percent more valve-stem life over other designs. The radial valve groove also extends the time between refreshing your heads by restricting rotation of the valve, preventing any accelerated wear by excess valve movement, like the three-groove is designed to allow.
Being a Square Isn’t Bad
The third style of groove is a “square-groove.” Also known as a “Chevy-groove,” this design has been around the longest. “The square groove is another popular OEM groove style. It is a very typical style groove, which has been used in a lot of engines for over 50 years,” says Urrutia.
As the name suggests, the profile of the square groove is, well, squared off. It is the widest of the grooves offered and has sharp edges – or “breaks” as Urrutia calls them – at the top and bottom of the groove.
“We have actually reengineered the square groove top and bottom edges, adding a small radius to them. This helps soften impact to the valve in the case of uncontrolled valve movement. It’s still not as forgiving as a radial groove, but it’s an improvement,” Urrutia explains.
It has been used in both OEM and racing engine use, and the fact that the square groove design restricts rotation by design like the radial groove makes it a valid choice in both stainless and titanium solid-stem valves.
The Right Choice
As with most engine components, there is no one all-around right answer.
“If you are looking for what’s great in a race engine, the radial groove is used in NASCAR, Formula 1, and a lot of the other high-end racing engine builders,” Urrutia reveals. “The radial is now as popular as the square-groove in our stainless valves, and is the most popular in titanium valves.”
Looking at the square groove as being a 50-year-old design, you can either take that as a time-tested and proven design, or one that is long in the tooth. Although, with Ferrea’s update to the square-groove design, it’s still a solid performer.
While the three-groove valves trail behind both of the other two styles in overall popularity, they do serve their purpose in OEM and high-performance street applications, and do so quite well. Whatever your intended engine use, picking the correct valve stem groove can both increase the life of your valves, and your cylinder head, so it’s worth putting in the time and effort to make an informed decision.