Camshaft Mysteries Revealed - How They are Made and What Their Specs Mean

Have you ever wondered about the specifications stated on the outside of a camshaft box, what they mean, or how to take advantage of them? Valve lift is often the topic that opens cam discussions. Fortunately, it’s meaning is fairly straightforward. Camshaft makers use valve lift to induce as much airflow through the engine as possible. Efficient cylinder heads on a 632 big-block Chevrolet, for example, will provide impressive flow characteristics up to 1.000-inch of valve lift—while most Mountain Motor Pro Stock teams seek valve lift well in excess of this—and increase it further by employing 2:1 rockers.

“But most Sportsman guys with a 632,” explains Jeff Sams of Lunati, “are reluctant to select a camshaft with such large valve lift because it is so destructive to parts.” Sams, a Pro Stock Mountain Motor owner, builder and tuner, bridles, “So, Lunati devised a happy medium using an .810-inch lift.” The .810 camshaft can operate with the normal 1.70/1.70:1 rocker ratio or with increased rocker ratios of 1:85/1.75:1 or even on 1:85/1:85:1. Sams continues, “Normally, it’s desirable to favor the inlet valve with more lift because it responds better. The exhaust valve, in contrast, doesn’t benefit as much from lift—it responds more to duration.”

Still, valve lift needs to be considered carefully. Let us assume we are tuning a drag race 632-ci big-block Chevrolet engine and our race camshaft provides a maximum inlet valve lift of .810-inch and maximum exhaust valve lift of .778-inch. This means the incoming charge has a maximum opening around the inlet valves of .810-inch and the exhausted gases flow through a maximum valve opening of .778-inch as they escape into the pipe.

Accounting for valve lash and a little pushrod deflection, valve lift is usually reduced by around .030-inch. Perhaps the first question should be whether or not the amount of valve lift specified on the cam box is sufficient to support the torque and rpm of my engine? In addition, the camshaft lobes, via the pushrods and rockers, open the valves, but it is the springs that close them.

Big-block and Pro Stock Mountain Motor exponent Chuck Lawrence of Jon Kaase Racing Engines suggests, “Knowing the amount of valve lift conveys many important spring requirements. The valve lift figure, for example, determines how tall the spring needs to be to enable it to open fully without becoming coil bound.

“It is also important to ensure the bottom of the spring retainer does not make contact with the valve stem seal or the valve guide. The key to selecting optimum spring pressures is to find the lightest pressure that will close the valve, keep it closed, and not allow it to chatter on the valve seat. Some of Kaase’s racing big-blocks might function with springs providing 500 psi of seat pressure (the pressure exerted on the spring when the valve is closed) and 1,200 psi of open pressure. Over time valve springs lose their strength so to avoid seat chatter we might change them when their seat pressure deteriorates to around 300 psi.”

Lobe Lift
The next term expressed on the camshaft box is lobe lift. Lobe lift and rocker ratio are a function of valve lift. Consider a lobe lift dimension of .476-inch and multiply it by 1.7 (the common rocker ratio of a big-block Chevrolet) and the resulting valve lift will compute to around .810-inch.

Increasingly, camshaft cores and journals have become larger in diameter to contribute greater stiffness to the valve train and also to accommodate larger lobes. Large lobes cannot be fitted in the engine block’s camshaft tunnel unless the journal diameters are even larger. In today’s racing engines, bearing journal diameters of 65mm are not uncommon, while professional teams are using nine-bearing 70mm camshafts in engine blocks that permit their burly proportions. Sufficient working clearance is usually their chief impediment. At these levels of competition, where the production of maximum power is the only objective, engine builders will try to find an engine block that will accept the largest cam bearing diameter, and therefore, the largest cam lobe. In addition, they will increase their rocker ratio to around 2:1.

But the greater the lobe lifts, the greater distance the lifter travels within its bore, and as a result, the greater it is affected by wear and tear. In an attempt to reduce lifter wear some race engine builders select a camshaft with moderate lobe lift and increase the rocker ratio to gain extra valve lift. Either way the spring is exposed to hard labor and needs replacing when its strength begins to fade.

Lobe lift is calculated by measuring the lobe’s overall dimension (toe-to-heel) and subtracting its base circle dimension. For example, the toe-to-heel dimension of the big-block cam specs displayed on the box is 1.462 inches and its base circle .986-inch. Its lobe lift, therefore, will be calculated as .476-inch.

Adv. Dur.
The term “Adv. Dur.” denotes advertised duration. Though not so commonly used as other references, it indicates seat-to-seat duration. Lunati measures its advertised duration of hydraulic camshafts at .006-inch. (valve off its seat), and often refers to it as duration at .006-inch. The advertised duration of solid camshafts is measured at .020-inch. in order to compensate for valve lash. 
Dur. @ .050-Inch
In contrast, the term “Dur. @ .050-inch” tappet lift is very common. Reducing the duration reduces the overlap, which in turn increases cylinder pressure.

Aided by a degree wheel and with a dial gauge indicator on the lifter, Jeff Sams explains how it is measured: “First you rotate the engine clockwise until your lifter is raised .050-inch. To eliminate the slack in the chain, turn the wheel counterclockwise by .100-inch and then clockwise .050-inch. Mark the number on your degree wheel and continue to rotate it clockwise, through its cycle, until the lifter falls back to .050in.”

Valve Lash
Valve lash is the mechanical clearance in valve trains with solid lifters. It is measured between the valve stem tip and the underside of the rocker arm. Valve lash is intended to provide the greatest amount of valve opening as the lifter travels over the high point—the nose—of the camshaft lobe, while still ensuring that the valve is tightly closed as the lifter travels over the low segment of the camshaft lobe, the base circle. Though some racers will attempt to gain a slight power advantage running looser lash settings, camshafts with aggressive lobes and excessive lash clearance risk damage to the valve stem tips, pushrod ends and lifters. It is also prudent to inspect the geometrical arc of the rocker arm as it sweeps across the valve tip.    

Center Line
The term “center line” refers to the point of peak lift of a camshaft lobe in relation to top dead center of the piston as measured in crank degrees. This can be changed by “degreeing” the cam. In this case, when the cam is degreed by advancing it 4 degrees, its center line will be 110 degrees. This means that the maximum lift of the Number One intake valve will occur when the Number One piston is positioned 110 crank degrees after top dead center.
To check the center line of the Number One intake lobe using a degree wheel, locate true top dead center of the Number One piston and set your pointer to zero on the degree wheel. Then place a solid lifter on the Number One intake lobe and position a dial gauge indicator on the lifter. Turn the engine clockwise until the lifter reaches peak lift and set the dial gauge to zero. Then turn the engine counter clockwise until the indicator falls .100-inch. Next, turn the engine clockwise until the dial gauge reads .050-inch and note the degree wheel reading. Continue to turn the engine clockwise (over peak) until the indicator reaches .050-inch after maximum lift and again note the degree wheel reading. Add these numbers together and divide them by 2. The resulting number represents the intake centerline.

Timing at .050-Inch Tappet Lift
The final rows of data on the box display valve timing data at .050-inch tappet lift. They are as follows: The inlet valve opens at 35 degrees before top dead center and closes 75 degrees after bottom dead center; the exhaust valve opens 90 degrees before bottom dead center and closes 34 degrees after top dead center.  

Spintron
The best tool ever devised for testing valve train components is the Spintron. It identifies and records crucial valve train characteristics such as valve bounce, tappet lofting, spring harmonics, pushrod deflection and more. Employed by all top teams where engine power is at a premium, the Spintron will check valve train performance from 500 to 20,000 rpm. It works in tandem with the dynamometer, and having one, or at least access to one, provides the race engine builder with a significant advantage. 

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The etchings on Lunati camshafts typically denote the type of cam (Voodoo); the part number (60512), which determines the grind profile; the day on which it was made (258th day of 2010); and the lobe separation angle (113 degrees).

Checking the straightness of the five journals of a 5160 induction-hardened camshaft. The center journal is the one first checked for straightness. It is permitted a tolerance no greater than .001-inch. If it meets tolerance requirements, usually the remaining journals will also pass the straightness checks. The blackness between the lobes usually indicates the induction-hardening process. In contrast, copper coating indicates carburizing, an Austempering process that also contributes a case hardening depth of around.130-inch.

A quick zap with the air hammer is used for straightening. The fuel pump lobe at the front and the distributor drive at the rear denote this cam will be used in a Chevrolet.

Lunati uses a Landis grinding machine to produce all of its premium and high-volume camshafts. The carriage securing the camshaft moves right to left and the grinding wheel moves fore and aft. Here the first three lobes are ground and the machine is stopped to check the lobes for toe-to-heal accuracy.

Simply program the part number into the Landis and 16 to 18 minutes later a perfect camshaft is born. After grinding the camshaft it is returned for further straightness checks.

Manual grinders are used to produce one-off and low-volume camshafts. This process is performed in two stages: roughing (as depicted here) and finishing.

Grinding speeds—the first essential of a quality camshaft maker. A key element in the finish-grinding process of a high-quality competition camshaft concerns grinding speed. If the speed is kept low, the quality of the grind will be high. If production numbers are allowed to trump quality and the grinding speeds are increased, the quality will be lower.

Measuring the toe-to-heal dimension to ensure the lobe has been ground to the correct size. The first check, interestingly, is to ensure the lobe is smaller than the journal, thereby ensuring the cam will fit the block!

With cam profiles already programmed in the inspection machine, it runs the ball along the lobes, comparing its findings with the design data. Its duties include measurements of taper, base circle, base circle run-out, toe-to-heal and lobe separation angles. In contrast, the essential attribute of the flat tappet cam lobe is, indeed, the taper on which the lifter rotates.

Polishing the journals is one of the final operations.

Don’t forget to read the spec card. It contains valuable details about the camshaft’s specifications as well as information about break-in lube, valve springs and how to find the center of the intake lobe.

Text and Photos by Sam Logan

Source: Drag Racer

Top Fuel Bikes from Around the World Compete in South Georgia

Text and Photos by Bryan Smyth

They came from Canada, England, Germany, Japan, Norway, Sweden, South Africa and all across the United States to take part in one of the biggest all-motorcycle drag races in history.

Headlining the Manufacturers Cup event this past November at South Georgia Motorsports Park (SGMP) were the mighty Top Fuel Motorcycles; 1,000-horsepower, fire-belching, two-wheeled monsters capable of knocking down five-second laps at 240-mph-plus on the all-concrete quarter-mile.

Twelve of the Top Fuel rides were on the grounds for the Haltech World Finals, but the clear dominator was Larry “Spiderman” McBride of Newport News, Virginia, the first man to the fives on two wheels when he turned the trick back in 1999 at Houston.

McBride ran quicker through each of three rounds of qualifying to place first in the eight-bike field with a 5.83 at 237.71-mph pass. Riding for Nitro Harley legend Ray Price, North Carolina’s Tommy Grimes started second with a 6.25/236.26 and third was four-time European Super Twin nitro champion Per Bengtsson with a 6.39/212.73 on The Beast, his screw-blown, 1,700cc ride from Klippan, Sweden.

Bengtsson was the driving force behind bringing five nitro race teams from Sweden and Norway to Cecil, Georgia. He made the decision to enter the Manufacturers Cup a year earlier, and then in the spring of 2012 he began to recruit additional teams to help defray the sizable costs involved.

With DHL Global Solutions handling the logistics, worldwide shipping company Hapag-Lloyd picked up a large, ocean-going container late in September from Bengtsson’s shop in Sweden, stuffed full of each team’s motorcycles, spare parts and tools, all bound for the Port of Savannah on Georgia’s coast before reaching SGMP by truck. Once delivered to the track a little more than a month later, the container was set on the pavement in the pits and served as the Nordic visitors’ garage and home away from home throughout their race weekend.

“We have our trucks at home like you do here, but here all of our things are together, so everyone has to have some discipline about things,” Bengtsson explained. “We are all friends, too, so we work around each other, but it’s a different feeling, that’s for sure.”
Bengtsson and 2008 Super Twin champion Svein Olav Rolfstad from Skreia, Norway, had both raced in the States previously. This trip, they and most others on the visiting teams took the opportunity to include some vacation time with wives, girlfriends, family members and even a few fans from their homelands, enjoying the warm weather and Southern hospitality.
Bengtsson and Rolfstad agreed that everyone in their group was very warmly received by U.S. fans and competitors alike.

“It’s been more than fun, especially because of all the enthusiasm from the spectators. Quite a lot of them are well aware of The Beast and know about us,” Bengtsson said. “We have already said we will be back, and now we have a manual on how to do it, so it should be much easier next year.”

That’s welcome news to McBride, who said he enjoyed the competition and felt encouraged by the international presence.

“I went down there (to the Swede/ Norwegian pits) to thank them all for coming. It’s not the first time, but it’s the first time in a long time,” the American star said. “I hope a lot more foreign teams come over here to race. They’re great people, they bring some great bikes, and they’re a great addition to the show.”

Once racing began, though, the show was all about McBride. He’d already secured his second Manufacturers Cup title when veteran nitro biker Chris Hand, the points leader heading into the World Finals, failed to qualify his Redneck Express machine for eliminations, but Spiderman never faltered. In his only run in the sixes all weekend, McBride went 6.026 at 235.43 to beat Sweden’s Trond Hoiberget in the opening round, and then improved to 5.835 at 227.46 on a second-round single after North Carolina native Tii Tharpe’s bike broke on the launch.

That set up a final-round faceoff for McBride against Rolfstad, who previously dispatched Bengtsson from round one and also made a solo pass in the semis when Texan Rickey House was unable to continue.

Unfortunately, it was Rolfstad’s turn to have trouble in the final, when his team discovered a leak from the engine at the end of his burnout. McBride then ran his best pass of the weekend with a 5.829 at 222.47 mph to take the win and officially wrap up his 11th career championship.

“You hate to see somebody break like that, especially when they came all the way from Europe to race, but at the same time, it does take a lot of the pressure off,” McBride admitted. “We had it hopped up there for the final, but we were having some cylinder-dropping problems, and I actually clicked it off early, but even with that it still was running extremely quick.”

Manufacturers Cup co-managers and promoters Jay Regan and Dave Schnitz were obviously very pleased after more than 800 tech cards were turned in for the third and final event of the 2012 series, but even more so with the trend toward foreign participation.

“It started with several race teams just coming as fans,” Regan explained. “But this year a lot of them wanted to step it up and come race with us, so we helped them with logistics and transportation and just tried to make it as easy and inviting as possible for them to compete.

“We think it adds a tremendous flavor to the event, so we’re actually going to try and further that by working collectively with the FIM/UEM, the European drag race sanctioning body, and see if we can turn this into a true world championship effort,” he added. “That would be the best possible scenario.”

DR-1303-BIKE Photo Captions

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Larry McBride dominated: He qualified first, set Low E.T./Top Speed and captured his 11th championship and second Manufacturer’s Cup title.

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Swede Trond Hoiberget of Super Twin Top Fueler fame glows eerie green on his launch.

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Four-time European champ Per Bengtsson unleashes The Beast, his infamous nitro parallel twin monster.

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Tommy Grimes riding for the legendary Ray Price Racing out of his HD dealership in Raleigh, NC.

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Rickard Gustafsson, a member of the Swedish Fuel Bike "Mafia"

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Chris Hand led the points coming into the race, but his Redneck Express failed to qualify.

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Iyo, Ehime, Japan-based Top Fuel rider Takeshi Shigematsu is a regular on the U.S. Nitro Bike scene.

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Texan Ricky House won his first round pairing, but got a no-show for round two.

The Essential Craft of Keeping Pro Stock Mountain Motors Running

Pro Stock Mountain Motors have cubic inch displacements of 820 to 825. Their capacities began much smaller, deriving from original equipment big-block engines of the ‘60s. But gradually the dimensions between their pan rails grew, allowing longer throw cranks to appear with connecting rods measuring 7.750 inches center to center and 5-inch bore centers with 4.770-inch-diameter pistons, all functioning within a deck height of 12 inches. Today’s Pro Stock engines operate on compression ratios of around 18:1, run on VP Race Fuel grade Q16, and generate in the region of 1,900 hp. Depending on weather conditions, they run quarter-mile elapsed times in 6.25 seconds at speeds close to 225 mph.

Jon Kaase Racing Engines has been a driving force in the development of these engines for as long as most can remember. From the beginning, when he worked with Dyno Don Nicholson, Kaase imposed uncompromising standards in race engine building. And his record of success has been impressive: He and his team have produced Pro Stock engines for 12 IHRA national championship winners, plus an NHRA Pro Stock title. Though their business now includes engine part sales to hot rodders, including the supply of the remarkable Boss Nine engine, the Winder, Georgia, firm still maintains about 20 Mountain Motor customers, refurbishing these formidable power plants after every 25 to 30 runs.

When reciprocating engine parts collide (usually pistons and valves) and a connecting rod or rods explode through the engine walls or the oil pan or both, foreign particles are immediately released into the oil stream to be sucked into the oil pump rotors. Rod bearings are often first to disintegrate, showering the pump with brass, copper and aluminum. Seasoned start-line observers will regale you with stories of inexperienced drivers breaking connecting rods at the starting lights and driving the entire length of the track, unaware that the vibration from the engine compartment was a signal of terminal distress. If the camshaft can still operate, usually the engine will continue to keep running—tearing itself apart all the way!

The chief concern about engine durability is the limited life of the connecting rods and also the condition of the skinny top pistons rings. The life cycle of these critical parts and others must be strictly observed in the rarified air of Mountain Motor Pro Stock racing.

In Kaase’s dynamometer cell, before this engine was tested, ace builder Chuck Lawrence leaned across to a visitor and said, “Have you ever heard one of these on a dyno before?” The visitor shook his head. “It’s pretty cool,” Lawrence insisted, “I never get tired of it.” He was right: that sound resides indelibly in the memory. Captured in the following images is the rebuilding process of a Mountain Motor Pro Stock engine.

Text and Photos by Sam Moore

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The engine is dismantled and the crankshaft is removed, cleaned and Magnaflux tested (a non-destructive fluorescent dye penetrant that reveals the location of surface and subsurface flaws).

New Mountain Motor engine blocks are available in either cast form from C&C Motorsports or in billet form from Dart. Here the billet block is exposed to the cleaning process

The art of cylinder honing is never taken more seriously than at Kaase’s. It is the key to gaining an edge on power output while maintaining a fine, consistent pattern of cross hatch scratches that lubricate the rings.

Piston pins are checked for straightness, and run-out is measured to 0.0001-inch (a tenth of one thousand inch). The run-out on the average pin is usually around this figure; if the indicator shows run-out of 0.0005-inch (five tenths of a thousand inch) the pin will be renewed.

Until five years ago Kaase used titanium connecting rods. Today they have been replaced mainly by aluminum. Shown on the left is an example of a titanium connection rod and on the right is the aluminum counterpart. The Diamond Pro Stock piston features inboard pin bosses, stiffening ribs, shorter pins and minimal skirts to decrease frictional loses. Friction is further reduced by the use of thin .8mm top rings and Napier-style second rings. Trend’s piston pins are coated in a diamond-like carbon and retained in the piston with single round wire locks.

The mighty Bryant billet crankshaft resides in the aluminum block and functions with aluminum rods, aluminum bearing caps and aluminum main caps. Aluminum is lighter than steel, and it also makes accurate line boring easier. When honing dissimilar metals (an alloy block with steel caps), the hone is inclined to push toward the softer metal.

The diameter of the forged pistons usually measures 4.770 inches. The small-bore holes around the perimeter of the CP pistons are gas ports. These allow combustion gases to enter the top ring grooves, imposing a force on the inner edge of the top rings and forcing them out onto the cylinder walls.

This five-stage oil pump (four scavenge, one pressure) has fine mesh screens embedded in the fittings at the ends of the number 12 lines to minimize the risk of particles entering the pump. But in the aftermath of a blow-up, fine debris usually penetrates to the heart of the system, and the lines and pump parts have to be cleaned and the rotors buffed smooth if necessary. Each of the four scavenge pumps conveys oil from assigned areas of the oil pan and transports it into the oil reservoir. The pressure pump (the one at the end) pumps oil from the bottom of the reservoir and into the filter. From the filter it is transported into the block.

The first part of the process of installing the valves is to check the continuity of the seal between the valve head and the valve seat. This is accomplished by applying red dye to the seats and lapping the valves into them. If continuity is broken and traces of red dye remain, the offending seats will be recut. Both inlet and exhaust valves are made of titanium. The diameter of the inlet valve measures 2.680 inches and the exhaust measures 2.040 inches.

Next, the tension of the triple valve springs is checked. Though the desired seat pressure and the installed height measurement change with different camshaft designs, Kaase’s most regular combination generates around 475 pounds at an installed height of 2.400 inches. Both inlet and exhaust valves, as well as the retainers, are made of titanium. Installed heights are maintained within 0.005-inch to 0.010-ichn by adding shims under the springs. Trend Performance provides shims in increments of 0.015, 0.030 or 0.060-inch.

Next, the triple valve springs are laid out for installation. Hardened seats are fitted between the spring and the aluminum head. Oil is applied to the valve stems and the valves are inserted into the cylinder head. Aided by a pneumatic valve spring compressor, the locks are carefully sandwiched between the valve stems and the retainers.

Copper spray from an aerosol can is applied to the top and bottom surfaces of the three-layer Cometic head gaskets, then the heads are fitted and tensioned to 130-140 ft-lb.

Pushrods are installed, WW billet rockers positioned, their shafts tightened to 35 ft -b and valve lash adjusted for engine warming on the dyno. Usually the clearance between the exhaust valve and the rocker is zero, and the clearance between the inlet valve and the rocker is 1/8th of a turn from tight. In this way, when the engine warms the inlet valve lash will measure 0.030-inch and the exhaust 0.020-inch.

With gaskets glued to the flanges, the intake manifold and carburetors are set in position

Curiously, the power of the vacuum pump can deflect the top skin of the alloy valve covers enough to propagate a crack around the plug holes. Welding the crack is not without its troubles. Invariably another crack will develop beside the weld.

The best solution for sealing the crack around the plug hole is to apply a special silicone sealer, the cost of which is around $80 for a small tube.

A vacuum pump can generate in excess of 22 inches of vacuum and is so effective it liberates 25 to 30 extra hp. It has the ability to improve ring seal and efficiently evacuates the turbulent air and oil mist from the under the reciprocating pistons in the crankcase, the valley area under the intake manifold, and the valve gear chambers on top of the cylinder heads. It often discharges to a canister through a port in the valley (under the intake plenum) or from the front face of the right cylinder head.

The effects of even the most powerful dyno-room fans are far removed from the pressurized air traveling through a hood scoop of a Pro Stock race car at 200 mph. Still, the dynamometer plays a vital role in assessing the engine’s condition: It allows for the examination of engine vacuum and oil pressure, of oil or water leaks, and it allows one to learn how the engine runs and whether it performs as expected. Jon Kaase’s notability rests not only on his gift for making big power, but also in his commitment to his customers—he presides over every test


Posted BY Drag Racer