We’ve spoken about the importance of getting your valvetrain geometry right when you build your engine. But, what happens after significant use? Obviously, in high-performance engines, maintenance needs to be performed because parts wear, and components need to be readjusted back into position.
In this Tech Tuesday video from Ferrea Racing Components, Zeke Urrutia details what you can look for during that preventative maintenance to ensure that your valvetrain is operating correctly and you aren’t heading towards a preventable disaster in the top end of your engine.
“We’re going to look at two patterns — one called the star pattern, the other called the sweep pattern,” says Urrutia. “Both can be seen when you start disassebling the engine and inspecting it for wear. [The patterns on the top of your valves] are a clear indication as to whether things are working properly or whether you’re starting to have issues.”
The Star Pattern — Not as Glamorous as it Sounds
“The star pattern is an incorrect pattern to have on the tip of your valve,” Urrutia explains. “There are several main factors that contribute to [the star pattern]. The first is too little, or loss of, spring pressure throughout the valvetrain. When your spring loses some of its pressure, rotational movement starts becoming a big issue.”
With too-little spring pressure, in addition to your valves rotating (which is perfectly normal) the valvespring itself can also rotate. That movement causes induces premature wear to the system. “What’s happening is the valvespring is starting to rotate in one direction and then the valve starts rotating in the opposite direction (or, they can both rotate in the same direction). That spring rotation causes the roller on the rocker to not run perfectly over the valvetip,” says Urrutia.
However, there can be other factors that would cause the rocker tip to be misaligned with the top of the valve: bad rocker geometry. Incorrect valvetrain geometry can cause the same star pattern on the tip of the valve. While not indicative of a loss or lack of spring pressure, the improper geometry can be just as big of a red flag.
“[The star pattern] is a clear indication that you’re having an issue,” Urrutia says. “If you have a star pattern, it can cause catastrophic failure of the engine. We’ll look over everything in that case: valvespring pressure, engine RPM, camshaft profile and if you have any power adders. Then we’ll put all the info together and pinpoint the issue.”
The desired pattern to see on your valve tip is known as the “sweep” pattern. As the name implies, it shows the rocker tip “sweeping” straight through the center of the valve tip. “The sweep is the correct pattern to have across the tip of your valve. That means that everything throughout your valvetrain is working correctly,” Urrutia concludes.