The controversy started quite a few years ago. Mechanical roller cam engines were spitting out roller lifters and killing engines at an unacceptable rate. Everybody had their own ideas on cause-and-effect diagnosis of the problem, along with solutions. For many racers and hot street engine builders, the answer was to convert to a bushing lifter.
While this has become a realistic solution for many engine builders, racers, and street engine builders, it’s not necessarily the universal panacea. Perhaps more importantly, the “solution” brings its own set of issues. Much like a coffee-table-sized jigsaw puzzle, there are multiple interrelated parts to this issue. We’ll cover as many as we can fit into this story.
Identifying the Issues
The first issue that needs to be addressed is understanding what caused all the problems with roller lifters in the first place. While the sources of the problem are numerous, it comes down to a combination of aggressive cam designs coupled with ever-escalating valve spring loads. Toss in loss of valvetrain control and you have the makings for a host of problems to arise. The real damage is done when a roller lifter fails and dozens of those tiny needle bearings escape. This causes catastrophic damage throughout the rotating assembly.
As an example, a friend suffered just such a failure in his street/strip 434ci small-block ’55 Chevy. The owner noticed the engine started to squeak about a mile from home but he chose to drive it the remainder of the distance. The noise was the lifter failing which subsequently destroyed the bottom end. The foreign debris put nasty gouge marks on the cylinder walls when the needles wedged between the piston skirt and the cylinder wall. This necessitated a complete rebuild along with, of course, a new cam and lifters.
Failures like this example have motivated engine builders and racers to replace roller lifter bearings with solid, one-piece bearings called bushings. In an interview with Jesel’s Dave Grob, he mentioned that Jesel is still very much in favor of needle bearing roller lifters, although Jesel now offers bushing versions because enough customers have asked for them. Grob says bushings, especially those running with high spring loads, require roughly five more horsepower (depending upon loads and RPM) to spin. This may not be significant in a 2,500-horsepower turbocharged engine but in a naturally aspirated class competition engine, that amount of power is a concern.
Listening to turbo cars on the starting line when they bang, I literally cringe. — Billy Godbold, Comp Cams Valvetrain Engineering Group Manager
Not A One-Size-Fits-All Solution
The advantages offered by bushings are fairly obvious, the largest of which is no minuscule needle-bearing missiles seeking deadly targets inside your engine. However, with bushings comes the same requirement that all the bushing manufacturers that we spoke to pointed to as critical. The racer or engine owner must keep track of the lash. This may seem simplistic, but even competitors with extremely expensive engines often overlook the obvious. During between-round or between-race maintenance, if the lash changes, that indicates something is amiss.
All the companies that we interviewed reinforced that it’s critical to keep a maintenance record of lash and to note if a given lobe has changed by more than 0.001-inch. If so, this is a warning flag that something in the system is wearing and should be investigated. This brings us to when a racer or street enthusiast should consider converting to bushing lifters. We posed this question to Comp Cams’ Director of Valvetrain Development Billy Godbold.
“If you run an engine with an ignition cut-out where the engine backfires on the starting line, you need a bushing lifter,” says Godbold. “If you run a turbo car with a boost controller where it bangs against the limiter and you hear the engine pop out the exhaust, you must run a bushing lifter. If your valvetrain is out of control, you most definitely need a bushing lifter.”
This means that those pressure excursions that you hear from an ignition cutout are directly affecting the lifters with severe impact loads. If you refer to the sidebar reference from the Bosch Automotive Handbook, you’ll see that one of the disadvantages of needle bearings is they are highly susceptible to impact loads. The result of these hammer-like loads can be a tiny indentation in one of the needle bearings. When this occurs, the needle will stop spinning and begin to slide. When this occurs, it creates unwanted friction, and will soon fail. Once that occurs, all the engine builder can do is sweep up the despair in a dustpan.
Advantages and Disadvantages of Roller Bearings
These remarks can be directly attributed to the Bosch Automotive Handbook – 3rd Edition on page 275:
Low static coefficient of friction Sensitive to impact loads
Low lubrication requirement Sensitive to dirt
One of Godbold’s time-honored examples of the consequences of loss of control is winter Olympic ski jumpers. As long as a jumper lands on the sloped portion of the ramp, they easily survive the landing. But, if they excel in their launch and land on flat ground, it’s going to be catastrophic to legs and ankles. The same is true of a roller follower. If it separates from the lobe and then reconnects on the closing ramp of the lobe, there will be minimal problems. If serious valvetrain deflection projects the lifter off the nose and the roller lands on the lobe’s base circle, the impact load will be catastrophic.
Typical Roller Lifter Specs
|Lifter Diameter||Wheel Diameter||Slower Wheel Speed|
|1.00 (wheel guided)||1.220||38.6%|
These percentages are based on the 0.750-inch wheel diameter. So a 0.904 Mopar lifter with an 0.815 wheel diameter will turn 8 percent slower than a 0.750-inch wheel diameter GM 0.842-inch lifter.
This is not to say there aren’t plenty of racers out there using mechanical roller cams with bushing lifters. As we alluded to earlier, there are caveats to this selection that must be attended to with close attention. Troy LaCrone is famous among the Midwest street elite, running dark blue, nitrous-assisted Camaros. The one that has received the most attention was his 572ci big-block Chevy, nitrous-assisted ’68 Camaro that consistently ran deep into the sevens with the help of a set of Morel Black Mamba bushing lifters.
LaCrone crashed that Camaro in testing and luckily was unhurt, but the car did not fare as well. He has since built a tube chassis ’69 Camaro, but his earlier F-body was famous for logging significant street miles with zero valvetrain issues. LaCrone competed for two years in Drag Week and finished second in the Pro Street class with a five-day average of 7.777 seconds at 172.9 mph. Drag Week is famous for culling out weak valvetrains and the number of engines wounded-in-action is legendary. Yet, LaCrone has completed two Drag Weeks with his Morel Black Mamba lifters that are still racking up street miles.
Once You’re Set On Bushings
Among the conditions that should be met when considering a set of bushing style lifters is to ensure a consistent volume of oil to the lifters at all times. Lake Speed, Jr. is a recognized tribologist, which is the fancy term for an oil engineer. He has some excellent recommendations for anyone considering the use of bushing-style mechanical or even hydraulic roller lifters.
According to Speed, bushings require high oil flow, so the first recommendation is to never restrict oil to the lifters. But just as importantly, a thick oil film is essential to creating the lubrication barrier necessary to minimize wear. “A semi-synthetic is actually really good for roller lifters,” says Speed.
“The needle bearings really like the higher pressure viscosity coefficient of the synthetic and mineral blend.” Speed also mentioned that viscosity is really important because bushings rely on a fluid film for protection. For these lifters, a 15W-40 or 20W-50 blend would be ideal.
All of this bushing lifter talk should not be misconstrued as a condemnation or criticism of roller-bearing lifters. The guys at Jesel, for example, are big supporters of roller-bearing lifters. If high spring loads and excessive RPM are part of a competition engine, then larger diameter roller lifters should also be an essential part of that plan. That should be matched with a larger cam core diameter as well.
According to Erson Cams’ Jack McInness, a 5mm increase in cam core (journal) diameter should be accompanied with a 0.020-inch wheel diameter increase to reduce wheel speed with the larger camshaft. EngineLabs followers may remember the story on Dan Jesel’s Equal 8, which was a custom-built clean-sheet-of-paper race engine that was aimed at Bonneville competition, where the plan is to spin the engine past 12,000 rpm.
To that aim, the engine uses one-inch-diameter lifters using a 1.220-inch roller wheel that is encased in cartridges fitted to the custom block machined with a massive 3.50-inch cam tunnel. These lifters use roller bearings and not bushings. In fact, they are the same style of roller bearings used in all Jesel lifters and what Jesel recommends if you are serious about building a competition engine.
On a more conservative level, this author has never experienced a failure with roller bearing lifters, despite running engines through some grueling competition, including two Pony Express open road racing events back in 1997 and again in 1998. We held our Lingenfelter-built 420ci small-block Chevy to 6,000 rpm over a period of 33 minutes where the oil temperature, even with an oil cooler, hit 300 degrees.
Despite this brutal treatment of the synthetic oil, the lash never changed after two full races and multiple street events. When we finally replaced the lifters, they appeared as if they could easily go another 20 years. This engine never exceeded 6,500 rpm, but we also ran some conservative spring pressures. The engine never exhibited valvetrain distress and we liberally changed oil and checked lash after every extended competition event.
We were using a set of Comp mechanical roller lifters that were merely splash-oil lubricated and not nearly as good as the company’s current Endure-X lifters using tool steel axles and fed with pressurized oil directly to the bearings. One other advantage to the newer generation roller lifters is that many of them are now fully rebuildable.
Between Comp, Isky, Jesel, Morel, Johnson, and the multiple other notable lifter companies, there are multiple options to choose from when deciding on the best lifter for your application. In the past, roller bearings were the only path. Now you have a choice.