When we hear about a new and notable design that improves a current product, we take notice. A recent announcement for the new COMP Cams Evolution hydraulic roller lifters is one that really made us sit up and pay attention. We’re told the idea began with a blank document on a computer engineering screen and developed into this new lifter that addresses many issues found within previous designs. We spoke to Chris Potter, valvetrain product manager at COMP Cams, to get some insights on the latest valvetrain component.
“Our first goal was to get the most consistent hydraulic roller lifter,” cites Potter. “Lifter noise upon startup has been a big concern from enthusiasts for a long time. Many customers have typically voiced concerns about the first few seconds of startup noise that can be inherent with first-generation-style lifters, especially if they have invested in a performance cam.”
It’s not just about the startup. A first-generation lifter design can be subject to different lifter-bleed issues related to high-performance use when the engine is operating. When you look at a standard hydraulic lifter design, the lifter’s hollow body travels on the outer wall, riding within the block’s lifter bore.
That same body is machined on the inside diameter to allow a volume of pressurized oil, plus the plunger, spring, and valving combination to force the pushrod upward using the engine’s oil pressure. Additionally, in a performance application, it will operate against increased valve spring pressures and greater valvetrain inertia.
“The internals of a hydraulic lifter are a precision fit assembly,” explains Potter. “The plunger is closely matched to the inside housing with minimal clearance, so the leak-down rate is not too great or too small. That is why you should never intermix the internal parts of an original-style lifter when you are cleaning and rebuilding a set of hydraulic lifters. Do each lifter individually, so the original assembly tolerances are maintained.”
Tight Tolerances Under Extreme Loads
Problems can occur, as a traditional plunger can “pump up” and hold the valves open. This causes the valves to float or the lifter to collapse. You can read many involved technical articles related to the theories concerning hydraulic lifters, but Potter mainly refers to the strength of conventionally designed roller lifters and how it affects their hydraulics.
Think of our testing process of each lifter kind of like buying a matched set of injectors. When you buy a set of lifters that have individually been pressure tested, you are guaranteed that one will perform as well as the one next to it in the box. – Chris Potter
“With a traditional-style lifter, the plunger operates directly within the lifter body, and that body is distorting all the time,” describes Potter. “What I mean is, every time a performance cam rotates, the acceleration loads — as it starts to come up the flank of the lifter — are incredible, and you wind up with distortion in the lifter body.”
Potter continues, “That distortion passes through to the internal bore where the plunger operates. Those precision clearances and tolerances are altered by the distortion, changing the bleed-down rate of the lifter. This new hydraulic cartridge design places the hydraulic chamber and puck assembly inside a separate cartridge.”
With the hydraulics now separated from the lifter’s outer body, Potter points out that this cartridge design allows them to take advantage of their own in-house machining technologies. “Not only have we stopped lifter distortion from affecting internal tolerances, but we can also introduce very close tolerances for the sake of bleed-down problems directly to the cartridge assembly.”
The Evolution In Lifter Design
The self-contained hydraulic cartridge is the key to the new patented engineering. “With this cartridge, we have increased the overall lifter’s strength and isolated the hydraulics. Now, lifter body distortion will not directly affect the puck,” says Potter.
Employing physics, the smaller volume of oil within the high-pressure chamber of the cartridge insert provides a stiffer, more responsive, and quieter lifter. A reduction in oil volume in this chamber design means less aeration of the oil and better bleed-down characteristics.
Compared to a conventional lifter, this smaller chamber and bleed-down allows more duration out of your cam. These characteristics are similar to a short-travel performance lifter.
“Unlike a COMP Cams short-travel lifter that only has puck travel of generally .080-inch, the Evolution lifter offers .150-inch of travel,” clarifies Potter. “An OEM lifter typically has a travel of .180- to .200-inch of travel, so this is a diverse full-travel lifter.”
Potter also tells us how each cartridge manufactured is tested before final assembly with the body. Primarily, they are looking at the bleed-down rate of each cartridge. “We pressurize the cartridge and put a specific load on the puck,” Potter describes. “The test process makes sure each cartridge goes through its expected travel range at the desired timespan expected.”
Lifter Preload And Lifter Seat Height
Seat height is the distance between the bottom of the roller and the seat where the pushrod meets. Potter adds that these dimensions are the same as previous lifters. “The Evolution lifter matches the seat height that replaces a late-model GM-LS or HEMI hydraulic roller lifter. The link bar lifters for early small-block or big-block Chevrolet applications match the seat height dimensions of Comp’s standard hydraulic roller lifters,” adds Potter.
Preload dimensions of these lifters can be diverse. You can preload your lifters with as little as .025-inch but Potter recommends that .100-inch is best for extreme-performance applications.
Potter spells out, “Because they’re full travel lifters, you should be able to run a standard push rod, short of going to some unique other dimensions in the engine such as a small base circle cam.”
Additional Design Benefits
There are a few additional strong points within the Evolution design. First, the outer lifter body is also thicker than a conventional hydraulic roller lifter. This provides 18-percent increased stiffness. Second, the hydraulic cartridge can be replaced by removing a snap ring retainer.
In the GM-LS applications specifically, the seat height remains the same, but we have lengthened the overall body height of the lifter so you can now run .675-inch of valve lift while still using the OEM-style lifter guide tray. – Chris Potter, COMP Cams
“As it pertains to the different engines that can utilize the Evolution lifter, we have mapped all of the oil galley locations within the specific engine blocks and have optimized the oil band located on the lifter body,” Potter notes. “This engineering will supply a consistent oil supply to the lifter’s internals throughout the lifter’s cycle.”
The roller portion of the Comp Evolution lifter also offers next-gen features, which Potter describes. “The roller wheel, axles, and needle bearings are a proven design we have utilized for years in our hydraulic roller lifters. What’s different about this, is we’ve added an oil passage from the lifter’s oil band to get extra oil directly to the wheel.”
He continues, “Some newer block designs have a more isolated cam which may affect oiling. This new oiling passage increases oil splash to the lifter wheel. Overall, this oiling design is implemented across the brands to give an extra lubrication factor.”
The lifters are available for small- and big-block Chevrolets and the GM-LS platform engine, as well as many Chrysler, Ford, Olds, and Pontiac engines. Even if your older engine block design does not use a roller-lifter guide tray that halts the rotation of the roller lifter, Evolution lifters are offered with link bars that maintain their clocked location.
Potter finishes, “In the GM-LS applications specifically, the seat height remains the same, but we have lengthened the overall body height of the lifter so you can now run .675-inch of valve lift while still using the OEM-style lifter guide tray.”
As long as the engineering computers are powered up at COMP Cams, you will continue to see new ideas evolve and move from the “drawing board” to the product lines. The further development of engine hardware like this unique patented lifter design offers improved strength and more efficiency, no matter the level of devotion to your love of performance or racing.