The camshaft is really the heart of every performance engine because the cam defines the engine’s breathing potential, its torque curve and peak horsepower. The camshaft controls when the valves open, how quickly they open, how far they open (with some help from the rocker arms), how long the valves are held open, and when the valves close. These are the all-important lift, timing and
duration specifications that describe the camshaft and how it compares to other camshafts.
Numbers alone don’t tell the whole story, though, because the camshaft has to work with the cylinder heads, valves, intake manifold and fuel delivery system to provide optimum airflow within the desired rpm range. Compression is also as factor, as is ignition timing, firing order, the weight of the vehicle, gearing and the kind of driving or racing the engine is being built for. Are you building a low speed torquer or a high rpm revver? All the parts that are chosen to go into the engine, including the camshaft, must be “right” for each other as well as the application – otherwise you’ll end up with an “also ran” that can’t keep up with the competition.
CHANGING CAM TECHNOLOGY
Though flat bottom solid and hydraulic lifter camshafts were the norm in the 1960s and early 1970s muscle car era, and are still used in many budget pushrod motors, the hot setup today is a roller lifter cam. Roller cams have two important advantages over flat lifter cams. One is reduced friction. That’s why most vehicle manufacturers use roller cams in their production pushrod engines today. A wheel rolling on a cam lobe generates much less friction, heat and wear than a slightly convex lifter rubbing on a lobe.
Multiply by 16 in a V8 engine and it adds up to a significant reduction in friction, which means less parasitic horsepower loss to turn the engine over and more usable horsepower at the flywheel.
The other advantage roller cams have over flat lifter cams is much more important from a performance standpoint. A roller lifter can handle a much steeper ramp on a cam lobe than a flat bottom lifter. This allows roller cams to open the valves more quickly so they can reach maximum lift earlier in the timing cycle. When you plot valve lift and duration on a graph, the area under the curve of a roller cam with an aggressive lobe profile will be greater than that of a flat lifter cam for the same lift and duration specifications. The higher ramp speeds and acceleration rates increase airflow, and consequently make more horsepower and torque.
Mark Campbell of Crane Cams says “Our Quick Lift technology has pushed camshafts to the limit as to how much lift you can design into a roller cam. The pressure angle created by the lobe against the roller determines the maximum rate at which you can push the valves open. So to take it to the next level, we have developed a new line of Quick Lift rocker arms to generate increased lift and duration.
“Moving the pushrod seat low in the rocker arms with respect to the rocker’s center of rotation changes the geometry as the valve opens. As the rocker oscillates, the contact point between the pushrod and seat moves upward and out. With a 1.6:1 rocker arm ratio, this new design actually increases the initial opening rate to about 1.72:1. By the time the valve gets to about .200? to .250? net lift, the ratio is back to around 1.6:1. It maintains that ratio through the rest of the lift profile. Then as the valve closes, the ratio increases back up to 1.72:1. The geometry of the Quick Lift rocker arm in effect provides a variable lift ratio.
“On newer engines like LS1, the Quick Lift technology can give up to four to six degrees more duration at .200? valve lift than you can get with a standard 1.6:1 fixed ratio rocker arm. If you have a cam that normally delivers 220 degrees of duration at .050 inch lift, with the Quick Lift rockers you can now get the same performance of a 224 to 226 degree cam. This is important on engines that are computer-controlled because you can reduce the seat-to-seat time for easier tuning. We’re getting the valve open much more quickly in the early part of the lift cycle to establish airflow into the cylinder. Then we’re holding the valve open longer and shutting it quickly to trap the charge.”
Campbell says the Quick Lift geometry is used in Crane’s shaft mounted rockers and LS1 rockers. The Quick Lift technology is also used in Crane’s Z-Series camshafts and all of their new competition series roller cams.
Another new product from Crane is a new line of high performance roller lifters called “Ultra-Pro.” The redesigned roller body uses a .187″ aircraft quality steel pin instead of screws to support the roller. Campbell says Crane ran a durability test that simulated 11,000 half mile runs. At the end of the test, the lifters still looked like new.
Also new from Crane is a “Power Tuner” tool for reflashing PCMs on late model engines that have aftermarket cams. Campbell says you have to change the PCM fuel and ignition curves to maximize camshaft performance when you change the cam in an LS1 or other late model engine.
“When General Motors tunes their engines for emissions compliance, they typically tune to only about 40% of the maximum emissions that are allowed to be on the safe side. So there’s a lot of wiggle room for tuning improvements without violating emissions. For example, on a stock PCM timing advance drops back to zero when the transmission shifts. With the Power Tuner tool, we can recalibrate the PCM so a certain amount of spark timing remains during the shifts to maintain peak performance. We also establish tuning points at 50 rpm intervals versus 200 rpm intervals for the stock programming.”
NEW ENGINES, NEW CAMS
Newer engines like the GM LS1, 4.6L Ford and Chrysler Hemi are all becoming players for aftermarket cams today, said “Scooter” (Paul) Brothers of Competition Cams. “With the new engines, we have to think differently about how we grind the cams and the geometry of the valvetrain. On many of these engines, you can’t decrease the base circle of the stock cam without screwing up valvetrain geometry on overhead cam engines.”
On pushrod engines, a cam grinder can increase the lift of a stock cam by regrinding and lowering the base circle. The overall lift of the cam is limited by the inside diameter of the cam bearing journals, so the lobes can’t be any higher than the surface of the cam bearings. By lowering the base circle, the effective height of the lobes is increased for more valve lift. The lifters ride a bit lower in their bores, so longer pushrods are needed to compensate for the change in geometry.
On overhead cam engines, the situation is different because the camshaft is in the head. It may actuate the valves directly via buckets over the tops of the valves, but on most late model engines cam followers or rockers are used to open the valves. If the base circle of the cam is reduced to increase lift, it repositions the followers or rockers so the tips are no longer in the right position.
Ideally, the valve end of a follower or rocker arm should be over the exact center of the valve stem when the valve is half open. If the tip is off-center at the mid-lift point, it will have an adverse affect valve lift as well as wear on the tip of the valve stem and rocker or follower.
Scooter says old know-how does not necessarily apply to today’s engines. “Even so, what we’re learning on the race track is helping us build better parts for all kinds of applications. Our NASCAR experience helped up develop thicker pushrods that flex less and beehive valve springs that have less mass.
“Everybody is using roller cams today because you can really push the valve speed up, especially with high lift rockers. But one thing you have to watch out for is too much horsepower. Some of these cams today can make more power than a stock block can safely handle. You’ll push the crank right out of the bottom of the block if the block can’t handle the loads.”
Scooter said one niche where he’s seeming more mechanical roller cams being used is in cruise night “retro” cars. Hydraulic lifters are better choice for the street, but some people like the noise and performance of a solid lifter roller cam.
Barry Rabotnick of Speed Pro/Federal-Mogul says his company sells a lot of street cams, mostly to what he called “entry level” enthusiasts who want a nice increase in power and performance without sacrificing driveability. He said 85 to 90% of their sales are flat lifter hydraulic cams for smallblock Chevys and Fords.
“We have about 200 part numbers in our product line. Some are emissions legal and some are for pre-emissions era engines. Our focus is to provide a good quality cam and good value, so we’re not going to have the latest grind for an LS1 with a turbo or applications like that. That’s not our market. Our customer is the guy who wants to step up a notch or two and wants a good rumpy idle with plenty of power.
“Our cams will compete with anybody else’s cams in this market. If a cam has the same lift and duration, it’s going to make the same power regardless of the name on the box. A decal on the window won’t make the car go faster. It’s the cam profile that makes the difference.”
Rabotnick said Speed Pro does sell some roller lifter cams (the 5.0L Mustang is one), but most of the demand he sees is for a traditional flat lifter performance cam. Speed Pro cams are available with new lifters, but most customers want just the cam. Even so, new lifters should always be used with a new camshaft. Lifters develop a wear pattern that matches the lobe, so if worn lifters are reused with a new cam it can accelerate both cam lobe and lifter wear.
“We also see a lot of demand for cams that deliver increased torque for applications like tow vehicles and 4WD trucks. But one segment where we have not yet seen much of a demand for performance cams is the sport compact car segment,” said Rabotnick.
Other camshaft manufacturers we interviewed for this article shared that observation. Though supposedly a hot and growing segment, the sport compact car market is still mostly a “bolt-on” market for easy-to-install parts like wheels, brakes, struts, spoilers, wings, cold air intakes, mufflers etc. Several aftermarket suppliers have introduced performance cylinder heads, camshafts, pistons and other internal engine parts for the most popular Honda and Mitsubishi engines, but demand has been limited. “The big numbers just are not there yet,” said one supplier.
The best market, most agree, is still the street performance market and all forms of racing (drag, circle track, off-road & marine). The traditional muscle car market is still strong in spite of the fact that it’s been almost 30 years since the last factory muscle cars were manufactured. Parts for these engines are still plentiful, easy to get and affordable, making these engines a mainstay of the aftermarket today.
NASCAR rules prohibit the use of roller cams. NASCAR engines have to run flat tappet cams. These engines typically run at 9,000 to 9,500 rpm and produce upwards of 750 horsepower. Most NASCAR teams run dual springs with seat pressures of 190 to 200 lbs. and open pressures of 500 to 600 lbs. at .750 inch lift. Pro Stock drag racers, by comparison, typically run triple springs with seat pressures of 375 to 475 lbs. with the valves closed, and up to 1,000 lbs. open.
The combination of high rpms and high spring pressure forcing the lifters against the lobes means an extremely smooth surface finish is needed for high performance flat tappet cam lobes to survive. Most NASCAR teams run steel cams with lobes that are polished to 4 microinches Ra or less.
One NASCAR engine builder we spoke with said he uses a two-step polishing process to produce a mirror-like finish on cam lobes and journals. After the cam has been ground, he hand polishes the lobes and journals with a special buffing wheel to make them as smooth as possible. Then he finishes the job with a secret “chemical” process that leaves a surface finish of 1 microinch Ra or less. That’s about as smooth as you can get, but that’s what it takes for a NASCAR cam to last a race (the cams are replaced after every race).
With roller cams, the surface finish is less critical. In fact, the surface should not be too smooth because it may cause the roller lifters to skid instead of roll. If this happens, it can produce a flat spot on the roller and ruin the lifter and the lobe. There must be some friction between the lobe and lifter to keep the roller turning, so additional polishing after the lobes have been ground is usually unnecessary with roller cams.
Though roller lifters run with much less friction than flat bottom lifters, lubrication of the roller lifters is still very important for the longevity of the roller bearings – especially on street-driven engines. Crower Cams recently introduced a redesigned roller lifter that adds a high pressure pin oiler hole for the roller bearings.
One trend that seems to be gaining momentum today is changing the firing order of a smallblock Chevy V8 to improve fuel distribution and power. John Steely of Howard Cams says switching the No. 4 and No. 7 cylinders in the firing order with a special camshaft works well for a lot of circle track racers. Whether this same trick works on the street or drag strip remains to be seen.
Rod Tubangui of Isky Cams, Gardena, CA, says Isky has just introduced 10 new performance cams for Chevy LS1 engines, and a new anti-pumpup hydraulic lifter. Tubanqui says the lifters have tighter tolerances and a stiffer spring inside to handle higher rpms.
Another new product from Isky is their “Rad Springs,” which offer increased durability thanks to better materials and a special nitride heat treatment. These work well with Isky’s “Red Zone” lifters, which come in .904? and .937? diameter sizes and are designed to handle higher spring pressures (over 800 lbs.).
“We also have a new line of performance springs for the more popular Honda engines, and are working on developing some camshafts for Honda and several other popular sport compact engines,” says Tubangui.
Hunter Betts of Enginetech in Carrollton, TX, says his company is offering a new line of high performance engine kits that offer a choice of six different cam grinds – all for the same price. “It makes ordering a lot easier and gives our customers the flexibility to pick a grind that best suits the application.”
Betts says the most popular cam grind is the low rpm high torque RV style cam. It’s a good choice for trucks as well as any street engines that needs better low speed acceleration and power. The next most popular cam is a mid-range cam that provides good power from 2,000 to 4,800 rpm. For those who want a “bumpty-bump” idle, Enginetech has a “stage three” cam. And for circle track racers, Betts says all-out performance and custom grinds are always available.
Betts says the market for cams today is changing. “We’re selling fewer individual components and selling more kits. Engine builders don’t want to stock parts anymore. They want to order a kit when a job comes in.”
Ed Plebanek of Topline in Chicago, IL, says Topline is now manufacturing its own lifters for domestic engines thanks to the recent acquisition of Hylift-Johnson Lifters’ manufacturing plant in Muskegon, MI. The plant is producing a full line of flat mechanical and hydraulic lifters, hydraulic roller lifters and OHC hydraulic last adjusters.
“We now have performance lifters for Chevys and Fords,” says Plebanek. “The lifters have a unique disk and seat design that can handle higher internal pressures with no leakage. The clip that holds the piston in the lifter body is also a stronger design so the lifters can safely handle higher valve spring pressures and rpms.”
A new line of performance lifters is also being offered by Schumann’s Sales and Service in Blue Grass, IA. “Camshaft suppliers have been having fits over poor quality lifters in recent years,” says Vern Schumann. “We decided to address this issue by developing an all-new line of premium quality lifters that include better materials, a better design and are 100 percent inspected.”
Schumann says his lifters use the highest metallurgical alloy provided, have correct and consistent heat treatment throughout, have a hollow shell that is 20 grams lighter than an OEM lifter, and feature a redesigned oil feed band and two .040? oil holes 180 degrees apart for better lubrication.
The parabolic crown surface on the bottom of his flat lifters is ground to an accuracy of .0002? at .0025? per radius diameter, with a 360 degree concentricity specification of .0002?. The crown surface is also mirror polished with no grinding marks, and is heat treated to a Rockwell C spec of 58 to 62.
“These are precision lifters that nobody else can match,” says Schumann. He also says the lifters are designed so they can be easily disassembled for cleaning. Applications include most popular Chevy, Ford and Chrysler V8 engines.
Schumann says he also has a new twin lube design H-11 tool steel crown cap lifter with a special diamond wear treatment for NHRA drag racing applications that run extremely high spring pressures.
“Some of these guys are now running ceramic lifters. But the ceramic lifters can shatter if you get any lash or slap in the valvetrain. Our tool steel lifters can take the higher spring pressures and pounding without failing,” Schumann says.
Dave Grob at Jesel Valvetrain in Lakewood, NJ, says his company has just introduced a new line of “double roller followers” for late model overhead cam engines such as the Cadillac Northstar V8, the sixty degree 4-valves-per-cylinder V6 in the Cadillac SRX, STS and CTS, the GM Echotech 4 cylinder engine, and Ford’s SOHC and DOHC 4.6L engines.
“We’re seeing more of these engines in drag racing, off-roading and even Bonneville. The OEM cam followers have a roller for the cam lobe but not the valve. Our followers have rollers for both to reduce friction and to handle higher spring pressures and rpms. These are a solid lash type of follower, so lash is adjusted with shims,” says Grob.