Dyno Shootout: Solid Roller Vs. Hydraulic Roller
When it comes to cars, everybody has got their favorite. Ford or Chevy, big blocks or small blocks, mufflers or straight pipes. If you like it, chances are somebody out there hates it, and that is just the nature of the beast. Of course, this carries over to engine components too, and one argument that has settled in (but isn’t settled) are the virtues of solid lifters versus hydraulic, and then solid roller lifters versus hydraulic roller lifters… One is known for easy setup and maintenance, the other for making big power. So which camp do you belong to?
As you might imagine, the first camshafts were of the solid lifter variety, and in the early days camshafts were not a single solid piece, but rather a rod with the lobes welded on. That all changed in 1908, right around the time when the first overhead camshaft designs started appearing. The first hydraulic lifters appeared in the 1930′s on Pierce-Arrow motorcars, and in the 1940′s solid roller lifters were designed for use in America’s bombers and fighter planes.
By the 1950′s hydraulic camshafts were becoming the norm, though all high-performance engines like the BOSS 302, 427 Cobra Jet and the 426 HEMI still used solid lifters, which produced more horsepower. One of the first cars to use a solid roller lifter though was the original Camaro ZL-1. It was not until the 1980′s that roller lifter technology would be applied to hydraulic lifters, with Ford and GM leading the way with their high-performance engines.
Most of today’s production engines use roller cam and lifter technology for additional power and reduced friction. Most of these cams are made as a one piece cam, some from steel that is usually induction hardened, some from ductile iron that is selectively hardened. This technology carries over to the high performance street and race engines we are all used to working with.
Suddenly it was the hydraulic roller camshaft that was at the forefront of high performance street engines, and the aftermarket moved quickly to flood the market with new hydraulic roller designs. Today’s hydraulic roller and solid roller lifter designs are far and away more advanced than their predecessors, with advanced designs of the related parts that reduce weight and friction, freeing up ever more horsepower.
Modern Roller Lifter Technology
The Elite Race Solid Roller Lifters feature some of the latest and greatest roller lifter racing technology.
With Comp Cam’s latest solid roller style setup, the Elite Race Solid Roller Lifters, they’ve managed to create a more durable solid roller lifter setup with an even better oiling system.
Made from 8620 steel and REM polished, these lifters feature a unique “column” design that allows engineers to eliminate unnecessary material, reducing the weight of each individual lifter to less than 100 grams while insuring the ultimate stiffness required in very high horsepower engines; “It takes less power to move something that weighs less, so the result is more power.”
Removable pushrod seats allow you to offset your pushrods, and 23 needle bearings better distribute the load, making this an even more versatile and durable type of solid roller lifter.
While technology has come a long way, it hasn’t eliminated the need for regular valve adjustments. These lifters are designed more for racing applications, but Comp Cams also offers a series of solid roller camshafts designed for the street.
The High Energy solid street roller camshafts offer a unique ramp approach from an all-out race roller cam, which allows for the use of less spring pressure, helping to ensure longevity. The opening and closing of the ramp still offers that deep, throaty, mechanical sound that solid lifter camshafts are known for. If you’re looking for more power, then there is an Xtreme Energy version of this street solid roller camshaft, which has.more aggressive lobe profiles resulting in greater horsepower. These designs have proven to be very street worthy and dependable.
Designed to work with the High Energy and Xtreme Energy cams are the Endure-X series of solid roller lifters. These lifters feature extra-durable tool steel axles that are resistant to wear. EDM oil injection ensures the axles and needle bearings remain well-oiled throughout the RPM range by pressurizing the oil towards the bearings and reducing wear and tear. Precision sorted needle bearings ensure an evenly-distributed load so no one area is unevenly worn out.
Now as you might imagine, a race roller camshaft setup is naturally going to make more power as it has a much more aggressive ramp rate than a street camshaft. The tradeoff comes from higher spring pressure, decreased durability from a street application, and the higher spring pressure can induce extra wear in the roller lifters, especially at idle.
A street roller cam is designed with a less aggressive ramp, requiring less spring pressure, putting less strain on the roller lifters at idle when the oil pressure is low and the lifter gets only splash lubrication. Our test involves two street roller camshafts, as opposed to racing camshafts, and while just about any cam will work on the street, you run the risk of wearing your lifters out prematurely with the wrong setup.
Either The COMP High Energy or Xtreme Energy solid roller cams and lifters make great power and work well for the weekend warriors who drive regularly on the street and as well as hardcore racers alike, However, neither of these combinations will completely the need for regular valve lash adjustment. The solid roller camshaft works quite well for power, but the regular valve adjustment is the small price you must pay for that added power.
In the early days of hydraulic roller cams and lifters there was a huge gap between solid and roller versions. Today’s hydraulic camshaft and lifter designs, including new anti-pump-up lifter technology has substantially closed the horsepower gap by minimizing what is commonly called “valve float” that once plagued high RPM hydraulic lifter applications.
This means new hydraulic roller camshafts are much stouter than they once were, and the lack of valve-train maintenance draws a lot of customers towards hydraulic lifters too. “We find it’s about an 80/20 split,” says Mays. “Most people would rather have the ease of setup and maintenance that comes with a hydraulic roller setup. But racers and those guys who really want that lumpy, old-school idle still prefer solid roller setups.”
Putting Down the Debate: Solid Roller VS. Hydraulic Roller Camshaft Shootout
Yet even with modern technology closing the gap between solid and hydraulic roller lifters, when it came time to choose a camshaft, inevitably, you were always left with a choice. The easy road would be the hydraulic roller camshafts, which provided a smoother engine sound as well as eliminating the need to set the valve lash.
The tradeoff though came from lost horsepower compared to running a solid roller setup. And so it has been for untold decades, with hot rodders having to choose between extra horsepower or fewer headaches when it came to maintenance.
But is there really a loss of power between the hydraulic and solid? We set out to compare two separate street camshafts from Comp Cams, one a solid roller lifter-style cam, the other using a hydraulic roller camshaft system.
Both cams were tested on an engine built around Dart’s SHP block, Packing 440cui, this massive motor was designed to accept most SBC Chevy crankshafts, and topped with Dart Pro 1 cylinder heads with Felpro head gaskets. This engine is all about making big horsepower without power adders and on pump gas, thanks to the Lunati flat-top pistons that provide a 10:1 compression ratio.
Keeping everything well-oiled is a Moroso deep-sump oil pan. On the dyno stand they ran it with a 750 CFM carburetor through Dart’s single plane intake which is matched up to their heads. And what roller camshaft setup would be complete without some Comp Cams Magnum roller rockers? It is all motor, relying heavily on the camshaft systems and cylinder heads to make power.
We’ll get to the results a little later. First, a refresher on roller lifter, solid, and hydraulic camshaft technology.
Hydraulic Lifter Lovin’
“Hydraulic lifters were developed so mechanics weren’t constantly kept busy readjusting valve trains every few thousand miles,” stated Mays. The first hydraulic lifters were also flat tappet-style lifters, and while it meant eliminating the need for constant readjustment, it wasn’t exactly great for making power.
What changed all that was the use of roller lifters with hydraulic camshafts in the 1980′s. Suddenly, you could make almost as much power as a solid roller setup, but without the constant readjusting.
The hydraulic lifter’s valve seat sits on type of a small hydraulic pump, and below that there’s a spring. This compression provides the clearance, or pre-load, in the range of .020” to .070”, that the valve needs, eliminating the need for constantly adjusting valve lash.
As Mays explains, “The laws of physics mean that a hydraulic camshaft setup can technically never produce as much lift as a comparable solid roller.” The compression of that piston inside the lifter means lost lift and lost power. We’ll see if the physics laws apply to this model. “Hydraulic roller technology has made very significant gains in the last few years, and when paired with roller-tip rocker arms, you are eliminating a lot of friction across the valve train, making up for that horsepower lost due to less lift. Depending on the engine setup the difference could be as little as 5-horsepower or as much as 50. Every engine is different.”
Do Me A Solid
“Simply put, the solid lifter is exactly what it sounds like: it’s solid, there’s no pump or give for the pushrod,” explains Mays.
Setting up a solid lifter valve train requires maintaining the proper valve adjustment, or valve lash: a small clearance between the tip of the rocker arm and the valve stem. Valve lash is necessary to maintain some clearance as the parts expand with heat, and to make sure that the valve is open as much as possible at the top of the camshaft lobe, and completely shut at the base circle.
While adjusting your valve lash is not the most complicated process in the world, running a solid lifter means occasionally taking off the valve covers and manually readjusting the valve lash on each of the 16 valves.
“Without readjusting the valve lash, you’re talking about premature wear and tear on the engine. You usually have to check the valve lash around 5,000 miles.” Now for drag racers, that works out to about 20,000 quarter-mile passes, but it’s common practice for drag racers to check the adjustment every few runs.
That’s a lot of racing, so adjusting the valves is going to be a less-regular occurrence for a car that’s reserved more for the street than the strip. As it just so happens, a solid roller camshaft setup has always been for those who want the most horsepower, and don’t mind doing a bit of extra work to get there. Question is, are you willing to go through the extra work and risk a little extra wear for that little power gain?
We’ve thrown around a lot of terms in the past few paragraphs that may leave a few of you scratching your heads. So let’s explain them, starting with duration. Duration is how long a valve is left open, expressed in degrees of camshaft rotation, 360 degrees forms a complete circle, right? So if a camshaft has duration of 240 degrees, it would be open for 240 degrees, or 2/3 of the crankshaft’s rotation. The longer a valve is open, the more air and fuel mix and the more exhaust gases are let out. Simple, right?
If duration is how long a valve is open, then lift is how wide that valve opens. More lift means the valve opens wider, again letting in more air and fuel, and letting out more exhaust. There are other specifications, like centerline and separation, but for this article all you really need to know is lift and duration to understand the power differences between a solid roller and hydraulic roller setup.
So let’s talk for a minute about the basic difference between flat tappet, hydraulic roller, and solid roller cams and lifters. Solid (mechanical) camshafts with roller lifters “have been around since the 1940’s and ‘50’s,” says Chris Mays, one of Comp Cams’ lead Engine Builder Technical guys.
However, the technology was not applied to hydraulic camshaft systems until the 1980’s, when Ford, GM, and Chrysler all came out with hydraulic roller systems right around the same time, setting off the feud between hydraulic and roller setups.
Roller lifters are exactly what they sound like, as there are literally little wheels attached to the ends of the lifters. The biggest benefit from this roller system is the reduced friction between the lifter and the camshaft, and this can be an easy 15-horsepower by itself.
But as Mays explains, there are other, less obvious benefits to this setup, “A roller lifter allows for a more aggressive ramp and a higher tappet velocity, in part because the lifter is following the cam profile exactly.” This allows for a more lift and more area on the camshaft, again resulting in more power.
“One of the design limitations of a flat tappet cam is that when used with a very aggressive lobe design the edge of the lifter digs into the cam lobe, causing premature wear and ultimately failure. The roller lifters eliminate this problem, make more power, and increase the reliability and longevity of the engine,” explains Mays.
The roller lifter setup is not new; the technology has been around for over half of the 20th century. But eventually the OEMs figured out how to apply the roller lifter technology to a hydraulic lifter setup, “and the aftermarket shifted that way,” says Mays.
The only real advantage a flat tappet setup has is the price, as they tend to be quite a bit cheaper. That’s because a roller setup requires more complicated lifters, the camshaft itself is more expensive because it is a ductile or steel core instead of cast and sometimes there is a lifter guide that sits in the engine valley between the cylinder heads. Extra parts mean extra cost, but what price can you put on extra power and reliability?
The added power and reliability convinced us that we definitely wanted to use roller lifters, but that doesn’t help solve the question of whether we should go with a hydraulic or solid roller camshaft setup. These days unless you are talking about an all-out race engine, most people prefer the convenience of hydraulic lifters over adjusting the valve lash on solid lifter setups. Conventional knowledge insists that these people are sacrificing a lot of horsepower…but is that really the case? And is the convenience worth it?
Jack McInnis of Dart Heads agrees, “Hydraulic camshaft technology has come a long way in the past few years. Most people we build engines for prefer the hydraulic camshaft setup. But nothing sounds like a nice solid lifter.”
We turned to Jack and Dart to build a 440 cubic-inch dyno mule so we could have ourselves a camshaft shootout between the solid roller setup and hydraulic roller.
Naturally, we turned to Comp Cams to provide us with our camshafts, and we weren’t disappointed with the results of either one.
For the hydraulic roller camshaft, we selected a COMP Cam’s Camshaft with a gross valve lift of .579 intake and .579 exhaust and a lobe lift of .381 on both intake and exhaust. The duration was 254 on the intake side and 266 exhaust.
That’s a pretty beefy camshaft, for sure, with plenty of lift and duration, but as we’ve already mentioned, because of the nature of the hydraulic camshaft’s plunger system, you’ll never see all that lift.
As for the solid roller lifter, we went with an even more aggressive ramp, with gross valve lift of .591 intake and .606 on the exhaust, lobe lift of .389 intake and .399 exhaust. The duration is the same as the hydraulic camshaft, 254 intake and 266 exhaust, so while the roller has a bit more lift, they’re fairly comparable camshafts. So how’d they do on the engine dyno?
All About the Numbers Alright so you did it, you made it all the way through the article and now you’re that much more knowledgeable when it comes to different kinds of camshafts. So how the hell do the two compare? First let’s run that bumpin’ thumpin’ solid roller camshaft. The solider roller setup made a peak of 578.7 horsepower at 6,200 RPM before dropping off, and registered 545.6 ft-lbs of torque at 5,000 RPM.Those are some impressive numbers for an all-motor, naturally aspirated setup, and most motors require some serious boost to see that kind of power. Surely the hydraulic camshaft can’t keep up…or can it?
With the same camshaft, the hydraulic roller camshaft held up surprisingly well, actually. For this final dyno run, Dart left the 750 carburetor but switched out the solid roller lifters and camshaft for the hydraulic. Everything else stayed the same, and the hydraulic camshaft managed to make a 570.3 peak horsepower at 6,200 RPM before it dropped off, and “only” registered 545.7 ft-lbs of torque at 5,000 RPM.
We put both charts next to each other and as you can tell, up to 5000 RPM the engines are pretty much even, which was not a surprise. What we didn’t expect to see was the peak horsepower on both camshafts to come in at the same RPM. The total difference in horsepower between the solid roller and hydraulic roller setup is just slightly over 8 horsepower. In fact, both cams actually made about the same ft-lbs of torque at the same RPM.
So what does it all mean? It means you no longer have to make a choice between solid and hydraulic roller lifter camshaft setups. The differences in power are actually negligible, coming down to the single digits in a serious street application.
While every engine is different what we’ve shown with this test is that two comparable camshafts, one a solid roller, the other a hydraulic roller, on the same 440cui engine will make almost the exact same horsepower and torque. You can’t argue with the numbers, so should we put the old myth to rest? Does a solid roller make any more or any less horsepower than a street-tuned hydraulic roller camshaft? We say with today’s hydraulic roller technology, no. Is that definitive enough?