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I borrowed this of the SUMMIT RACING site, I figured some of the newer guys could use the info

The Basics On Choosing the Right Street Cam
Not so long ago, the bigger is better philosophy reigned supreme regarding camshafts. The result was over cammed engines that sounded great and could crank serious top-end power, but were not very streetable and couldn’t idle to save their lives.

But thanks to modern cam technology, you can come pretty darn close to the Holy Grail of street bumpsticks—cams that make high rpm power, have good low-end torque and drivability, decent vacuum for power brakes, and that loping idle we all love. Camshaft theory is a complex subject that can take a book-length article to explain. We’re going to concentrate on the basics you’ll need to know to choose a good street cam.

Lift and Duration
Lift and duration are the primary factors that determine a cam’s profile. Lift is the amount a cam lobe actually moves a valve off its seat, and is measured in fractions of an inch. Duration is the amount of time a cam keeps a valve off of its seat, measured in degrees of crank rotation.
Lift and duration combined determine total open valve area—the space available for air and fuel to flow into and out of the combustion chamber. The more valve area open to flow, the more power an engine can theoretically make. The trick is to “size� a cam to optimize valvetrain events for your particular engine combination and vehicle.

Cam Sizing
Virtually every cam maker uses duration to rate camshafts. When someone talks about a “big� cam, they are referring to cams with longer duration. This keeps the valves open longer, increasing midrange and top-end power at the expense of low-end torque. A shorter duration cam does just the opposite. Because it doesn’t keep the valves open as long, a smaller cam boosts low rpm torque and drivability. There are two ways to measure duration:
Advertised Duration is the figure you usually see in the cam ads and hear about at those late-night bench races. The problem with advertised duration is cam makers use various methods of measuring it, making it difficult to compare cams from different makers.
Duration at .050 measures duration at .050 inches of valve lift. Since all cam grinders use this measurement, it’s a much more accurate way to make a comparison. Two cams may be very close in advertised duration, for example, but make peak power at different rpms. Summit Racing uses duration at .050 ratings to help you better compare the wide variety of cams it carries.
Lobe Separation
Lobe separation is the number of degrees that separate the peak lift points of the cam’s intake and exhaust lobe. Like duration, lobe separation helps determine the cam’s rpm range. Generally, a cam with wider lobe separation (112-116 degrees) will make power over a wider rpm band. A cam with narrow lobe separation (under 112 degrees) is biased toward peak power and operates within a narrower rpm band.For the street, you want a cam with a fairly wide lobe separation for the best power production over the engine’s entire rpm range. Go too narrow with lobe separation and you may end up with an engine with a peaky powerband biased to high rpm horsepower—not the hot ticket for a street car.

Flat Tappet vs. Roller
Now that you have an idea of what lift and duration are, let’s muddy things up by comparing flat tappet and roller lifter cams. Flat tappet cams use a lifter with a slightly curved bottom that slides against the cam lobes. Virtually every V8 engine built before the late 1980s came with a flat tappet cam; they are reliable and relatively inexpensive. With literally hundreds of profiles to choose from, finding a good flat tappet cam for your street car is not difficult.
Roller cams are hardened steel cams that use lifters with a roller, or wheel, that rolls over the cam lobes. This design dramatically decreases valvetrain friction and wear, and allows designers to create profiles that offer more lift without increasing duration. That means a roller can make more midrange and top end power than a flat tappet cam of the same duration without sacrificing bottom end power. If you need proof that roller cams are better, ask the OEMs what they put in their engines nowadays.

Hydraulic or Solid?
Flat tappet and roller cams for overhead valve engines are available with hydraulic and mechanical lifters. Hydraulic lifters are self-adjusting; they use an oil-damped, spring-loaded plunger to help maintain valve lash (the distance between the valve stem and the rocker arm tip). Hydraulic lifter cams are quiet, require virtually no maintenance, and transmit less shock to the valvetrain. Their main drawback is a tendency to “pump-up� (overfill with oil) and cause the valves to float, or stay open too long, at high rpm. Valve float kills power, and can lead to engine damage if you keep your foot planted in the throttle.
Mechanical, or solid, lifters are not self-adjusting. They rely on a properly set up, adjustable valvetrain to maintain proper valve lash. Because solid lifter cams are less susceptible to valve float at higher rpms, they are ideal for more radical street and racing profiles. The price of running solid lifters is periodic adjustment of valve lash and increased valvetrain noise.

Overhead Cam Considerations
Overhead cam engines, like Ford’s 4.6 and 5.4 liter Modular V8s, follow the same rules regarding cam selection as overhead valve engines. The primary difference is how valve lift is determined. Overhead cam engines don’t use rocker arms, so there is no multiplication effect to increase valve lift (cam lift x rocker arm ratio = valve lift). Thus, cam lift and valve lift are the same.
The only way to increase lift with an overhead cam is to reduce the diameter of its base circle (the rounded bottom portion of the lobes). Changing the base circle increases valve lash as well, requiring the use of taller lash caps on the valve stems to maintain proper valve lash. This is a fairly involved process, which is a big reason why you’ll see many street cams for overhead cam engines with various duration figures but the same lift number.

Information, Please
Your sales rep or cam maker will need to know the following parameters to help you get the right cam grind for your particular vehicle and engine combination:

Vehicle Weight: You can run a bigger cam in a lightweight vehicle because less low-end torque is necessary to get it moving. Heavy vehicles need cams that emphasize low-end power.
Rear Axle Gear Ratio and Tire Size: If you have a bigger (numerically higher) gear ratio, you can use a bigger cam. Lower “economy� gears work better with a mild cam that makes power at low rpm. Tire height is important because it helps determine the final drive ratio.
Transmission Type: Cams for automatics have to work over a broader rpm range. Manual transmissions can tolerate a bigger cam biased to making peak power. The cam’s powerband should match torque converter stall speed or clutch “dump� rpm.
Engine Size and Compression: A cam’s profile is affected by displacement. Most cam descriptions for small block Chevys, for example, are based on 350 cubic inch engines. Put a cam in a 383 stroker and it will act like a milder grind. The more duration a cam has, the more compression is needed to maintain proper cylinder pressure at low rpm.
Airflow: Your cam needs to work within the airflow capabilities of the engine. The airflow characteristics of the cylinder heads (amount, intake/exhaust ratios, port work, etc.), induction system, and exhaust system are all factors.
Power Adders: Superchargers, turbos, and nitrous require special cam profiles to take advantage of the extra power potential. In general, cams made for use with power adders are ground with wider lobe separation to take advantage of the extra cylinder pressure.
Rocker Arm Ratio: Going to a larger rocker arm ratio increases valve lift on overhead valve engines. The cam should be tailored to work with your specific ratio to avoid slapping valves into pistons or trashing valve springs.

Cam Comparison: 5.0L Mustang
Let’s compare two popular hydraulic roller cams for a 5.0L Fox-body Mustang that specs out as follows:
•3,400 pound vehicle weight, 5-speed, 3.73 rear axle gear
•306 cubic inch small block, 9.5:1 compression with EFI, aluminum heads, shorty headers, and cat-back exhaust

Cam One: Ford Racing X303
(Part Number FMS-M6250X303)
Advertised Duration: 286 degrees intake/exhaust
Duration at .050: 224 degrees intake/exhaust
Valve Lift (with 1.6 rocker): .542 inches intake/exhaust
Lobe Separation: 110 degrees
Powerband: 2,500-6,200 rpm

Cam Two: Comp Cams Xtreme Energy OE Roller 35-514-8
(Part Number CCA-355148)
Advertised Duration: 266 degrees intake, 274 degrees exhaust
Duration at .050: 216 degrees intake/224 degrees exhaust
Valve Lift (with 1.6 rocker): .545 inches intake/.555 inches exhaust
Lobe Separation: 112 degrees
Powerband: 1,600-5,600 rpm

If you look at just advertised duration, the Comp grind looks less aggressive than the Ford Racing cam. But when you check duration at .050, both cams are virtually the same. This is an example of why duration at .050 is a much better comparison method.
Where our cams diverge is in lift and lobe separation. The Comp Xtreme Energy grind offers far more lift and a relatively wide 112 degree lobe separation, so it makes good power across the rpm band. The extra lift and duration on the exhaust side helps improve the small block Ford’s poor exhaust breathing. Comp recommends the cam for cars with 3.27-3.73 gears, Mass Air systems, and mild modifications like a larger throttle body, headers, and free-flowing exhaust. Either a five-speed or an AOD automatic with a mild stall converter would work with this cam.
The Ford Racing X303 has slightly lower lift figures, but is ground with a narrower 110 degree lobe separation. That makes the cam more biased toward high rpm power production. In fact, peak horsepower rpm comes at a rather lofty 6,500 rpm, almost 1,000 rpm higher than the Xtreme Energy cam. Ford Racing says the X303 should be used with a five-speed manual transmission.
We hope this little primer gave you the knowledge you need to choose the right cam for your street ride. If you want to get a PhD in camshaft-ology, companies like Crane, Comp Cams, and Iskenderian have loads of information on their websites to help you become Dr. Bumpstick. Happy cam shopping!


Additional Sources

http://forum.grumpysperformance.com/viewtopic.php?f=52&t=324


Comp Cams: www.compcams.com
Crane Cams: www.cranecams.com
Ed Iskenderian Cam Co.: www.iskycams.com
Lunati Cams: www.lunaticamshafts.com

heres a differant sites info

Misunderstood Ideas
Overlap and Compression- A very common idea, although for the most part incorrect, is that overlap bleeds off compression. Overlap, by itself, does not bleed off compression. Overlap is the angle between the exhaust closing and intake opening and is used to tune the exhaust's ability draw in additional intake charge as well as tuning idle vacuum and controlling power band width. Cylinder pressure is generated during the compression cycle, after the intake valve has closed and before the exhaust opens. Within practical limits, an early intake closing and late exhaust opening will maintain the highest cylinder pressure. By narrowing the Lobe Seperation Angle 'LSA' for a given lobe duration, the overlap increases, but the cylinder pressure can be increased as well. Thus cylinder pressure/compression can actually increase in this scenario, by the earlier intake closing and later exhaust opening. By increasing duration for a given LSA, the overlap will increase, the intake closing will be delayed, and the exhaust opening will occur earlier. This will decrease cylinder pressure, but the decrease/bleed-off of compression is not due to the overlap, it is due to the intake closing and exhaust opening events.

Adjusting Lash on Mechanical/Solid Cams- If valve lash changes significantly over time, then something is wrong. Cam wear is very slight, along the order of .002 or less. If the lash setting changes more than .005 then there has been a component failure (loosened hardware or actual mechanical failure). Lash settings should be taken/adjusted at the same temperature and same order as the previous or original setting. This is the only way to rule out expansion/contraction of the components from temperature changes. This temperature delta is usually the culprit of most valve lash dilemmas. At initial start-up and break-in of a new set-up: cam, lifters, rockers, pushrods, valve job, etc., the lash may move around during the break-in procedure and for a short time after. This is because all the parts are seating into their new wear patterns. Once this occurs, the lash setting should stay steady.

Hydraulic Lifter PreLoad- Hydraulic lifters are intended to make up for valvetrain dimensional differences as well as providing a self-adjusting method of maintaining valve lash, or rather the lack of. By setting the valvetrain so the lifter plunger is depressed slightly, the lifter is able to compensate for these differences, making a convenient hassle-free valvetrain set-up. For performance applications, lifter preload is not needed or wanted. As rpm's increase, the lifter has a tendency to bounce over the back of the lobe as it comes back down from the maximum lift point. The pressurized oil fills the lifter body to account for this bouncing. Eventually, after several engine revolutions, the oil can completely fill the lifter body and the plunger will be pushed up to its full travel (pump-up). Higher oil pressures can amplify this problem. With the lifter pre-loaded, this can cause a valve to run off it's seat and can cause piston clearance issues if and when pump-up occurs. By setting the valvetrain at 'zero' preload, lifter pump up is eliminated and in most cases, the cam will rev higher. Ford tech articles in late 60's actually urged 'stock' class racers to run .001-.003 lash on hydraulic cams.

Piston To Valve Clearance- Piston clearance is a function of lobe geometry and phasing to the piston. Cam lift should not be a deciding a factor in clearance issues. Valves will hit the piston in the overlap period, while exhaust is closing and intake is opening. Exhaust clearance problems will typically occur just before TDC and intake just after TDC, not at max lift. Some cylinder head venders and other component manufacturers advertise a max duration or lift before clearance issues arise. This is very misleading. Maximum safe duration is a totally bogus value, and is completely worthless without knowing anything about the ramp rates or actual timing/phasing events of the installation. At least with maximum safe lift, the vendor can a apply a rediculously fast ramp at a very early opening/closing and arrive at a somewhat meaningful measurement, but without knowing the design specifics the information is still next to useless.

Custom Ground Camshafts- When the performance of a particular engine combination is wanted to be optimized, the camshaft design parameters are calculated from the engine and vehicle specifications to perform within specific conditions. Let me emphasize that last statement, 'within specific conditions!'. In no way was total maximum power for the engine implied. The intent is to maximize performance within the intended design parameters. If that means taking a pro-stock motor and wanting to run it from 2000-5000 rpm, then so be it.

The camshaft's seat timing events, ramp rate, and lift are directly related to the intake and exhaust flow capabilities, crankshaft geometry, static compression, rpm range, as well as other criteria. A camshaft selected in this manner, becomes personalized to that particular engine combination. Usually a custom grind is selected as an intake lobe and exhaust lobe with a particular phasing to each other (lobe separation angle, LSA) and sometimes a specified amount of advance or retard is built in. Although, it could easily end up having completely reengineered lobe characteristics, requiring new lobe masters with specialized ramp requirements. It is possible for an off-the-shelf camshaft to be a classified as a 'custom'. If the cam design is calculated for a particular combination and an off-the-shelf part number fits the bill, then for all practical purposes that part number is a 'custom' cam (but only for that particular set-up).

Typically, cam catalogs do not specifically list custom ground camshafts, because the possibilities are endless. They stick to particular series or families of camshafts. The superstock grinds come closest to an off-the-shelf grind that is truly optimized for a combination. There will be small differences due to header sizes and engine builder's 'secrets, but usually the catalogs are pretty close to a good baseline. Likewise, brand to brand, the grinds will be very similar because of the 'class' dictated combinations and the flow characteristics being so well documented

Degreeing Camshafts- There is no special magic involved for degreeing a camshaft during installation, but this is not the same thing as random advancing, retarding, or installing the gears 'lined up'. Degreeing a camshaft involves definite known values for valve events. Typically this is specified as an Intake Centerline or as opening/closing events at specific lobe lifts. This is done to insure the cam is installed per specific requirements, such as a recommendation from an engine builder or the vendor's data sheet for that camshaft grind. Manufacturing tolerances and shop practices do not guarantee that the cam matches the data sheet, when installed at crank gear 'zero'. The cam will usually need to be advanced or retarded to the correct location. If it is correct, at crank gear 'zero', then the cam has still been degreed. It just did not require any additional tweaking to meet the requirements. This is what degreeing a cam is all about; the verification of the installation. A common mis-used term is the 'straight-up' installation. Typically this is described as installing the cam at crank gear 'zero'. This is 100% wrong. Straight-up refers to the Intake and Exhaust Centerlines being the same. In other words the cam will have no advance or retard at the installation, regardless of the amount of advance/retard ground in by the vendor. In reality, the cam may have to be advanced or retarded (from crank gear 'zero') significantly to arrive at a straight-up installation.

Exhaust System Diameter and Engine Horsepower- A popular idea is to select/size the exhaust system components to the engine's horsepower output. This idea typically attributes a header diameter or an exhaust system diameter to a particular horsepower level. To resolve this, look at how an engine operates and consider one cylinder. The cylinder will move a volume of air based on its crankshaft geometry, rpm, and sealing capability. The amount of air that can enter the cylinder is dependant on the intake flow capability, crank geometry, rpm, and valve timing as a minimum consideration. Likewise, the amount of air that exits the cylinder is dependent on the same characteristics.

An engine's output is usually thought of in terms of horsepower. Actually, an engine produces torque, and the horsepower is calculated through a units conversion. The amount of torque an engine can produce is directly related to the amount of cylinder pressure generated. This is all affected by the same previous characteristics (intake and exhaust capability, crank geometry, rpm, valvetiming, etc). So basically an engine's power output is about air exchange capability. Using this line of thinking, look at the exhaust path again. The exhaust system is more reflective of the engine's ability to move air, as opposed to horsepower numbers. Engine output does not address the breathing aspects of the engine and is probably not a good rule to use for exhaust sizing.

There is a very good reason that tuners/engineers/specialist have attempted to assign exhaust to intake relationships around 70-80% for a typical natural aspirated set-up. In non-detailed terms, it is a range that offers a good balance for power capability. Other relationships, such as 1:1, are used and they work very well, but these methods have to be applied and tuned for very specific circumstances. This relationship does not stop on the flow bench, it goes all the way from the intake path opening to the exhaust system termination. In short, try to maintain exhaust sizes that are inline with the intake capability. Also, do not stop your analysis at the intake and exhaust paths. If the engine already has the camshaft, look at the valve events. If the specs favor a restricted exhaust (indicated by early and wider exhaust openings with wider lobe separation angles), then size it accordingly by using exhaust components with smaller cross-sections. If the valve timing specs favor the intake, then the engine needs some serious exhaust flow capability which is only possible with larger cross-sections.

This section was written with natural aspirated combinations in mind. However, by using the 'air exchange' rationale, it becomes apparent why forced induction engines typically benefit from increased exhaust flow capability. Also, look at the nitrous combinations. The intake system remains virtually unchanged, yet with the major increases in cylinder pressure it acts like a substantially larger engine on the exhaust side, requiring earlier exhaust openings and/or higher exhaust flow capability.

Pushrod Length- Incorrect pushrod length can be detrimental to valve guide wear. Most sources say that centering the rocker contact patch on the valve stem centerline at mid valve lift is the correct method for determining the optimum pushrod length. This method is wrong and can actually cause more harm than good. The method only applies when the valvetrain geometry is correct. This means that the rocker arm lengths and stud placement and valve tip heights are all perfect. This is rarely the case. To illustrate this, think of the valve angle and the rocker stud angle. They are usually not the same. If a longer or shorter valve is installed, then the relationship of the valve tip to the rocker stud centerline has changed. Heads that have had multiple valve jobs can also see this relationship change. Note, the rocker length (pivot to tip) remains unchanged, so the rocker contact patch will have to move off the valve centerline some particular distance for optimum geometry to be maintained.

The optimum length, for component longevity, is the length that will give the least rocker arm contact area on the valve stem. In other words the narrowest wear pattern. This assures that the relationship is optimized and the rocker is positioned at the correct angle. This means that the optimum rocker tip contact point does not necessarily coincide with the valve stem centerline, and probably will not. What is the acceptable limit for being offset from the valve stem centerline? That will depend on the set-up. A safe margin to strive for is about +/-.080" of the centerline of an 11/32 diameter valve stem. This means that no part of the wear pattern should be outside of this .160" wide envelope. As the pushrod length is changed, the pattern will change noticeably. As the geometry becomes closer to optimum, the pattern will get narrowest. If the narrowest pattern is too far from the valvestem centerline, then the valve to rocker relationship has to be changed. In this case, valve stem length will need to change.

What is meant by basic RPM?
The camshaftÃ-s basic RPM is the RPM range within which the engine will produce its best power. The width of this power band is approximately 3000 to 3500 RPM with standard lifter cams, and 3500 to 4000 RPM with roller lifter cams. It is important that you select the camshaft with the ìBasic RPM Rangeî best suited to your application, vehicle gearing and tire diameter.

Camshaft duration and why is it important?

Duration is the period of time, measured in degrees of crankshaft rotation, that a valve is open. Duration (at .050î lifter rise) is the deciding factor to what the engineÃ-s basic RPM range will be. Lower duration cams produce the power in the lower RPM range. Larger duration cams operate at higher RPM, but you will lose bottom end power to gain top end power as the duration is increased. (For each ten degree change in the duration at .050î, the power band moves up or down in RPM range by approximately 500 RPMÃ-s.)

Advertised duration and duration at .050î lifter rise (Tappet Lift)?

In order for duration to have any merit as a measurement for comparing camshaft size, the method for determining the duration must be the same. There are two key components for measuring durationó the degrees of crankshaft rotation and at what point of lifter rise the measurements were taken. Advertised durations are not taken at any consistent point of lifter rise, so these numbers can vary greatly. For this reason, advertised duration figures are not good for comparing cams. Duration values expressed at .050î lifter rise state the exact point the measurement was taken. These are the only duration figures that are consistent and can accurately be used to compare camshafts.

How does valve lift affect the operation of an engine?

Lift is the distance the valve actually travels. It is created by the cam lobe lift, which is then increased by the rocker arm ratio. The amount of lift you have and the speed at which the valve moves is a key factor in determining the torque the engine will produce.

Camshaft lobe separation and how does it affect the engine?

Lobe separation is the distance (in camshaft degrees) that the intake and exhaust lobe centerlines (for a given cylinder) are spread apart. Lobe separation is a physical characteristic of the camshaft and cannot be changed without regrinding the lobes. This separation determines where peak torque will occur within the engineÃ-s power range. Tight lobe separations (such as 106°) cause the peak torque to build early in basic RPM range of the cam. The torque will be concentrated, build quickly and peak out. Broader lobe separations (such as 112°) allows the torque to be spread over a broader portion of the basic RPM range and shows better power through the upper RPM.

Intake and exhaust centerlines?

The centerline of either the intake or exhaust lobe is the theoretical maximum lift point of the lobe in relationship to Top Dead Center in degrees of crankshaft rotation. (They are shown at the bottom of the camshaft specification card as ìMAX LIFT.î) The centerlines of the intake and exhaust lobes can be moved by installing the camshaft in the engine to an advanced or a retarded position. Generally speaking, the average of the intake and exhaust lobe centerline figures is the camshaft lobe separation in camshaft degrees.

How does advancing or retarding the camshaftÃ-s position in the engine affect performance?

Advancing the cam will shift the basic RPM range downward. Four degrees of advance (from the original position) will cause the power range to start approximately 200 RPM sooner. Retarding it this same amount will move the power upward approximately 200 RPM. This can be helpful for tuning the power range to match your situation. If the correct cam has been selected for a particular application, installing it in the normal ìstraight upî position (per the opening and closing events at .050î lifter rise on the spec card) is the best starting point.

Why is it necessary to know the compression ratio of an engine in order to choose the correct cam?

The compression ratio of the engine is one of three key factors in determining the engineÃ-s cylinder pressure. The other two are the duration of the camshaft (at .050î lifter rise) and the position of the cam in the engine (advanced or retarded). The result of how these three factors interact with one another is the amount of cylinder pressure the engine will generate. (This is usually expressed as the ìcranking pressureî that can be measured with a gauge installed in the spark plug hole.)

It is important to be sure that the engineÃ-s compression ratio matches the recommended ratio for the cam you are selecting. Too little compression ratio (or too much duration) will cause the cylinder pressure to drop. This will lower the power output of the engine. With too much compression ratio (or too little duration) the cylinder pressure will be too high, causing pre-ignition and detonation. This condition could severely damage engine components. It is important to follow the guidelines for compression shown on the application pages of the catalog.

How does cylinder pressure relate to the octane rating of todayÃ-s unleaded fuel?

In very basic terms, the more cylinder pressure we make the more power the engine will produce. But look out for the fuel! TodayÃ-s pump gas is too volatile and cannot tolerate high compression ratio (above 10.5:1) and high cylinder pressure (above approximately 165 PSI) without risking detonation. Fuel octane boosters or expensive racing gasoline will be necessary if too much cylinder pressure is generated.

How does an increase in rocker arm ratio improve the engineÃ-s performance?

The lobe lift of the cam is increased by the ratio of the rocker arm to produce the final amount of valve lift. A cam with a .320î lobe lift using a 1.50:1 ratio rocker arm will have a .480î valve lift (.320î x 1.50 = .480î). If you install rocker arms with an increased ratio of 1.60:1, with the same cam, the lift would increase to .512î (.320î x 1.60 = .512î). The engine reacts to the movement of the valve. It doesnÃ-t know how the increased lift was generated. It responds the same way it would as if a slightly larger lift cam had been installed. In fact, since the speed of the valve is increased with the higher rocker arm ratio, the engine thinks it has also gained 2° to 4° of camshaft duration.

The end result is an easy and quick way to improve the performance of the existing cam without having to install a new one.
Remember, whenever you increase the valve lift, with either a bigger cam or larger rocker arm ratio, you must check for valve spring coil bind and for other mechanical interference. Please review the previous sections concerning these matters

Must new (Standard Design) lifters always be installed on a new camshaft?

YES! All new standard hydraulic and mechanical camshafts must have new lifters installed. The face of these lifters have a slight crown, and the mating lobe surface they ride on has been ground with a slight taper. The purpose of this is to create a ìspinningî of the lifter as it rides on the lobe. This is necessary to prevent premature wear of the lifter and lobe. Therefore, these parts will be mated to one another during the initial break-in period. Used lifters will not mate properly, causing the lobe to fail.

If you are rebuilding an engine and plan to re-use the existing cam and lifters (in the same block) it can be done, as long as the lifter goes back on the same lobe it is mated to. If the lifters get mixed up, they cannot be used, and a new set will be required. The new lifters would also have to go through the break-in procedure to mate to the old cam.

Can used roller lifters be installed on a new camshaft?

YES. ìRollerî lifters are the only ones that can be re-used. This design lifter has a wheel (supported by needle bearings) attached to the bottom of it. The lobe the roller lifter rides on does not have any taper. This is a very low friction design and does not require the lifter to mate to the cam. As long as the wheel shows no wear, and the needle bearings are in good condition, the ìhydraulic rollerî or ìmechanical rollerî lifter can be re-used.

What engine oil and lubricants should I use?

Crane Cams does not recommend the use of synthetic oils during the initial break-in period for a new camshaft. Use a good quality grade of naturally formulated motor oil during this period. If you choose to use synthetic oil after the engine has been broken in, change the oil filter and follow the oil manufacturerÃ-s instructions.

When using either regular oil or synthetic it is important to pick the weight oil that best matches your engine bearing clearances, the engineÃ-s operating temperature, and the climate the vehicle will be operating in. Use the oil manufacturerÃ-s recommendation to satisfy these conditions. Crane Cams offers several lubricants to aid during the critical break-in procedure, and to prolong the engineÃ-s life.

Should I use ìOil Restrictorsî in my engine?

No, Crane Cams does not recommend the use of oil restrictors. The oil is the life blood of the engine, not only lubricating but cooling the engine components as well. For example, a valve spring builds in temperature as it compresses and relaxes. This increase of temperature affects the characteristics of the springÃ-s material, and if excessive, will shorten the life of the spring. Oil is the only means the spring has for cooling.

How do I prime the engineÃ-s oiling system?

It is critical that the engineÃ-s oiling system be primed before starting the newly rebuilt engine for the first time. This must be done by turning the oil pump with a drill motor to supply oil throughout the engine. If this is done with the valve covers off, you will be able to see that the oil is being delivered to the top of the engine and to all the valve train components.

Ive posted more info here

http://forum.grumpysperformance.com/viewtopic.php?f=52&t=324

http://forum.grumpysperformance.com/viewtopic.php?f=69&t=2645&p=6834#p6834

http://forum.grumpysperformance.com/viewtopic.php?f=52&t=2875

http://forum.grumpysperformance.com/viewtopic.php?f=69&t=9930

http://grumpysperformance.com/
 

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So much great information!
 

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great article !!!
2 cents:

oems went to roller cams becus lubrication problems with high oper temps (emission,poor airflow underhood,etc) resulted in excess lobe wear and warantee costs. those who watch a temp gauge and use 180 t-stats can get 99% of roller perf for 25% of the cost from flat tappets.
used flat tappets can be run on a new cam if old tappet is not concave and "conditioned" with 6oo sandpaper (see gm chevypower manual)
prelube new cams and any cam that has not been run for 60 days (14 days if u r anal like me) using a 1/2 drillmotor on top off an old distrib that the gear teeth r removed- most "tools" sold for this create an internal oil leak=no good. seen many good cams (some mine) lost by dry start. never do anything without proper lube!!!
b4 u replace ur cam with a "better" one, try retiming ur oem cam 6-8 degrees advanced from stock. this has worked wonders on some. probably will pass tailpipe sniff too. most better mpg
if u do buy a new cam,be honest with urself and the cam guy (ok to lie over beer) a race cam is junk for street-sounds great/works lousy.
 

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Im a newb when it comes to my vette, but i have to thank you any way, since it must have takin a while to type the 411 out,
and after i read it a few times i might actually learn some thing from it....:partyon:
 

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Good post grumpyvette! :thumbsup:

Here is also a great explanation of torque from the vettenet: I hope this is not a repeat! :D

Torque and Horsepower - A Primer
From Bruce Augenstein, [email protected] There's been a certain amount of discussion, in this and other files, about the concepts of horsepower and torque, how they relate to each other, and how they apply in terms of automobile performance. I have observed that, although nearly everyone participating has a passion for automobiles, there is a huge variance in knowledge. It's clear that a bunch of folks have strong opinions (about this topic, and other things), but that has generally led to more heat than light, if you get my drift :). I've posted a subset of this note in another string, but felt it deserved to be dealt with as a separate topic. This is meant to be a primer on the subject, which may lead to serious discussion that fleshes out this and other subtopics that will inevitably need to be addressed.

OK. Here's the deal, in moderately plain english.

Force, Work and Time
If you have a one pound weight bolted to the floor, and try to lift it with one pound of force (or 10, or 50 pounds), you will have applied force and exerted energy, but no work will have been done. If you unbolt the weight, and apply a force sufficient to lift the weight one foot, then one foot pound of work will have been done. If that event takes a minute to accomplish, then you will be doing work at the rate of one foot pound per minute. If it takes one second to accomplish the task, then work will be done at the rate of 60 foot pounds per minute, and so on.

In order to apply these measurements to automobiles and their performance (whether you're speaking of torque, horsepower, newton meters, watts, or any other terms), you need to address the three variables of force, work and time.

Awhile back, a gentleman by the name of Watt (the same gent who did all that neat stuff with steam engines) made some observations, and concluded that the average horse of the time could lift a 550 pound weight one foot in one second, thereby performing work at the rate of 550 foot pounds per second, or 33,000 foot pounds per minute, for an eight hour shift, more or less. He then published those observations, and stated that 33,000 foot pounds per minute of work was equivalent to the power of one horse, or, one horsepower.

Everybody else said OK. :)

For purposes of this discussion, we need to measure units of force from rotating objects such as crankshafts, so we'll use terms which define a *twisting* force, such as foot pounds of torque. A foot pound of torque is the twisting force necessary to support a one pound weight on a weightless horizontal bar, one foot from the fulcrum.

Now, it's important to understand that nobody on the planet ever actually measures horsepower from a running engine. What we actually measure (on a dynomometer) is torque, expressed in foot pounds (in the U.S.), and then we *calculate* actual horsepower by converting the twisting force of torque into the work units of horsepower.

Visualize that one pound weight we mentioned, one foot from the fulcrum on its weightless bar. If we rotate that weight for one full revolution against a one pound resistance, we have moved it a total of 6.2832 feet (Pi * a two foot circle), and, incidently, we have done 6.2832 foot pounds of work.

OK. Remember Watt? He said that 33,000 foot pounds of work per minute was equivalent to one horsepower. If we divide the 6.2832 foot pounds of work we've done per revolution of that weight into 33,000 foot pounds, we come up with the fact that one foot pound of torque at 5252 rpm is equal to 33,000 foot pounds per minute of work, and is the equivalent of one horsepower. If we only move that weight at the rate of 2626 rpm, it's the equivalent of 1/2 horsepower (16,500 foot pounds per minute), and so on. Therefore, the following formula applies for calculating horsepower from a torque measurement:

Torque * RPM

Horsepower = ------------

5252


This is not a debatable item. It's the way it's done. Period.
The Case For Torque
Now, what does all this mean in carland?

First of all, from a driver's perspective, torque, to use the vernacular, RULES :). Any given car, in any given gear, will accelerate at a rate that *exactly* matches its torque curve (allowing for increased air and rolling resistance as speeds climb). Another way of saying this is that a car will accelerate hardest at its torque peak in any given gear, and will not accelerate as hard below that peak, or above it. Torque is the only thing that a driver feels, and horsepower is just sort of an esoteric measurement in that context. 300 foot pounds of torque will accelerate you just as hard at 2000 rpm as it would if you were making that torque at 4000 rpm in the same gear, yet, per the formula, the horsepower would be *double* at 4000 rpm. Therefore, horsepower isn't particularly meaningful from a driver's perspective, and the two numbers only get friendly at 5252 rpm, where horsepower and torque always come out the same.

In contrast to a torque curve (and the matching pushback into your seat), horsepower rises rapidly with rpm, especially when torque values are also climbing. Horsepower will continue to climb, however, until well past the torque peak, and will continue to rise as engine speed climbs, until the torque curve really begins to plummet, faster than engine rpm is rising. However, as I said, horsepower has nothing to do with what a driver *feels*.

You don't believe all this?

Fine. Take your non turbo car (turbo lag muddles the results) to its torque peak in first gear, and punch it. Notice the belt in the back? Now take it to the power peak, and punch it. Notice that the belt in the back is a bit weaker? Fine. Can we go on, now? :)

The Case For Horsepower
OK. If torque is so all-fired important, why do we care about horsepower?

Because (to quote a friend), "It is better to make torque at high rpm than at low rpm, because you can take advantage of *gearing*.

For an extreme example of this, I'll leave carland for a moment, and describe a waterwheel I got to watch awhile ago. This was a pretty massive wheel (built a couple of hundred years ago), rotating lazily on a shaft which was connected to the works inside a flour mill. Working some things out from what the people in the mill said, I was able to determine that the wheel typically generated about 2600(!) foot pounds of torque. I had clocked its speed, and determined that it was rotating at about 12 rpm. If we hooked that wheel to, say, the drivewheels of a car, that car would go from zero to twelve rpm in a flash, and the waterwheel would hardly notice :).

On the other hand, twelve rpm of the drivewheels is around one mph for the average car, and, in order to go faster, we'd need to gear it up. To get to 60 mph would require gearing the wheel up enough so that it would be effectively making a little over 43 foot pounds of torque at the output, which is not only a relatively small amount, it's less than what the average car would need in order to actually get to 60. Applying the conversion formula gives us the facts on this. Twelve times twenty six hundred, over five thousand two hundred fifty two gives us:

6 HP.

Oops. Now we see the rest of the story. While it's clearly true that the water wheel can exert a *bunch* of force, its *power* (ability to do work over time) is severely limited.

At The Dragstrip
OK. Back to carland, and some examples of how horsepower makes a major difference in how fast a car can accelerate, in spite of what torque on your backside tells you :).

A very good example would be to compare the current LT1 Corvette with the last of the L98 Vettes, built in 1991. Figures as follows:

Engine Peak HP @ RPM Peak Torque @ RPM

------ ------------- -----------------

L98 250 @ 4000 340 @ 3200

LT1 300 @ 5000 340 @ 3600


The cars are geared identically, and car weights are within a few pounds, so it's a good comparison.

First, each car will push you back in the seat (the fun factor) with the same authority - at least at or near peak torque in each gear. One will tend to *feel* about as fast as the other to the driver, but the LT1 will actually be significantly faster than the L98, even though it won't pull any harder. If we mess about with the formula, we can begin to discover exactly *why* the LT1 is faster. Here's another slice at that formula:

Horsepower * 5252

Torque = -----------------

RPM


If we plug some numbers in, we can see that the L98 is making 328 foot pounds of torque at its power peak (250 hp @ 4000), and we can infer that it cannot be making any more than 263 pound feet of torque at 5000 rpm, or it would be making more than 250 hp at that engine speed, and would be so rated. In actuality, the L98 is probably making no more than around 210 pound feet or so at 5000 rpm, and anybody who owns one would shift it at around 46-4700 rpm, because more torque is available at the drive wheels in the next gear at that point.

On the other hand, the LT1 is fairly happy making 315 pound feet at 5000 rpm, and is happy right up to its mid 5s redline.

So, in a drag race, the cars would launch more or less together. The L98 might have a slight advantage due to its peak torque occuring a little earlier in the rev range, but that is debatable, since the LT1 has a wider, flatter curve (again pretty much by definition, looking at the figures). From somewhere in the mid range and up, however, the LT1 would begin to pull away. Where the L98 has to shift to second (and throw away torque multiplication for speed), the LT1 still has around another 1000 rpm to go in first, and thus begins to widen its lead, more and more as the speeds climb. As long as the revs are high, the LT1, by definition, has an advantage.

Another example would be the LT1 against the ZR-1. Same deal, only in reverse. The ZR-1 actually pulls a little harder than the LT1, although its torque advantage is softened somewhat by its extra weight. The real advantage, however, is that the ZR-1 has another 1500 rpm in hand at the point where the LT1 has to shift.

There are numerous examples of this phenomenon. The Integra GS-R, for instance, is faster than the garden variety Integra, not because it pulls particularly harder (it doesn't), but because it pulls *longer*. It doesn't feel particularly faster, but it is.

A final example of this requires your imagination. Figure that we can tweak an LT1 engine so that it still makes peak torque of 340 foot pounds at 3600 rpm, but, instead of the curve dropping off to 315 pound feet at 5000, we extend the torque curve so much that it doesn't fall off to 315 pound feet until 15000 rpm. OK, so we'd need to have virtually all the moving parts made out of unobtanium :), and some sort of turbocharging on demand that would make enough high-rpm boost to keep the curve from falling, but hey, bear with me.

If you raced a stock LT1 with this car, they would launch together, but, somewhere around the 60 foot point, the stocker would begin to fade, and would have to grab second gear shortly thereafter. Not long after that, you'd see in your mirror that the stocker has grabbed third, and not too long after that, it would get fourth, but you'd wouldn't be able to see that due to the distance between you as you crossed the line, *still in first gear*, and pulling like crazy.

I've got a computer simulation that models an LT1 Vette in a quarter mile pass, and it predicts a 13.38 second ET, at 104.5 mph. That's pretty close (actually a tiny bit conservative) to what a stock LT1 can do at 100% air density at a high traction drag strip, being powershifted. However, our modified car, while belting the driver in the back no harder than the stocker (at peak torque) does an 11.96, at 135.1 mph, all in first gear, of course. It doesn't pull any harder, but it sure as hell pulls longer :). It's also making *900* hp, at 15,000 rpm.

Of course, folks who are knowledgeable about drag racing are now openly snickering, because they've read the preceeding paragraph, and it occurs to them that any self respecting car that can get to 135 mph in a quarter mile will just naturally be doing this in less than ten seconds. Of course that's true, but I remind these same folks that any self-respecting engine that propels a Vette into the nines is also making a whole bunch more than 340 foot pounds of torque.

That does bring up another point, though. Essentially, a more "real" Corvette running 135 mph in a quarter mile (maybe a mega big block) might be making 700-800 foot pounds of torque, and thus it would pull a whole bunch harder than my paper tiger would. It would need slicks and other modifications in order to turn that torque into forward motion, but it would also get from here to way over there a bunch quicker.

On the other hand, as long as we're making quarter mile passes with fantasy engines, if we put a 10.35:1 final-drive gear (3.45 is stock) in our fantasy LT1, with slicks and other chassis mods, we'd be in the nines just as easily as the big block would, and thus save face :). The mechanical advantage of such a nonsensical rear gear would allow our combination to pull just as hard as the big block, plus we'd get to do all that gear banging and such that real racers do, and finish in fourth gear, as God intends. :)

The only modification to the preceeding paragraph would be the polar moments of inertia (flywheel effect) argument brought about by such a stiff rear gear, and that argument is outside of the scope of this already massive document. Another time, maybe, if you can stand it :).

At The Bonneville Salt Flats
Looking at top speed, horsepower wins again, in the sense that making more torque at high rpm means you can use a stiffer gear for any given car speed, and thus have more effective torque *at the drive wheels*.

Finally, operating at the power peak means you are doing the absolute best you can at any given car speed, measuring torque at the drive wheels. I know I said that acceleration follows the torque curve in any given gear, but if you factor in gearing vs car speed, the power peak is *it*. An example, yet again, of the LT1 Vette will illustrate this. If you take it up to its torque peak (3600 rpm) in a gear, it will generate some level of torque (340 foot pounds times whatever overall gearing) at the drive wheels, which is the best it will do in that gear (meaning, that's where it is pulling hardest in that gear).

However, if you re-gear the car so it is operating at the power peak (5000 rpm) *at the same car speed*, it will deliver more torque to the drive wheels, because you'll need to gear it up by nearly 39% (5000/3600), while engine torque has only dropped by a little over 7% (315/340). You'll net a 29% gain in drive wheel torque at the power peak vs the torque peak, at a given car speed.

Any other rpm (other than the power peak) at a given car speed will net you a lower torque value at the drive wheels. This would be true of any car on the planet, so, theoretical "best" top speed will always occur when a given vehicle is operating at its power peak.
"Modernizing" The 18th Century
OK. For the final-final point (Really. I Promise.), what if we ditched that water wheel, and bolted an LT1 in its place? Now, no LT1 is going to be making over 2600 foot pounds of torque (except possibly for a single, glorious instant, running on nitromethane), but, assuming we needed 12 rpm for an input to the mill, we could run the LT1 at 5000 rpm (where it's making 315 foot pounds of torque), and gear it down to a 12 rpm output. Result? We'd have over *131,000* foot pounds of torque to play with. We could probably twist the whole flour mill around the input shaft, if we needed to :).

The Only Thing You Really Need to Know
Repeat after me. "It is better to make torque at high rpm than at low rpm, because you can take advantage of *gearing*." :)
 

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erratum: "visualise that one pound weight"

weight is inconsequential here...resistance of one pound applied to one foot lever as stated is all that counts...

50% of cycle will be 'raising' the weight, requiring energy input---the other 50% of ccycle will result in energy "production"...visualize TWO one pound weights at 180 degrees apart--does this DOUBLE the power????..
 

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Discussion Starter #11
theres a BUNCH of factors that must be looked at...

http://victorylibrary.com/mopar/intake-tech-c.htm

http://victorylibrary.com/mopar/cam-tech.htm

http://forum.grumpysperformance.com/viewtopic.php?f=52&t=965&p=1705#p1705

http://forum.grumpysperformance.com/viewtopic.php?f=69&t=2645&p=6834#p6834

http://www.rbracing-rsr.com/runnertorquecalc.html

http://headerdesign.com/extras/engine.asp#Intake_Manifolds

http://www.bgsoflex.com/intakeln.html

http://www.wallaceracing.com/runnertorquecalc.php

http://www.mercurycapri.com/technical/engine/intake/pt.html



the calculators above will allow you to match the engines intake port length and flow rates

heres some basic rules of thumb as they say


keep the EFFECTIVE durration of the cam matched to the compression ratio so that the DYNAMIC cpr stays in the 7.5:1-8.5:1 range and the overlap matches the chart below
these are the valve timeing overlap ranges that are most likely to work correctly
trucks/good mileage towing 10-35 degs overlap
daily driven low rpm performance 30-55degs overlap
hot street performance 50-75 degs overlap
oval track racing 70-95degs overlap
dragster/comp eliminator engines 90-115 degs overlap

but all engines will need the correct matching dcr for those overlap figures to correctly scavage the cylinders in the rpm ranges that apply to each engines use range.look carefully at this chart


example
http://dab7.cranecams.com/SpecCard/DisplayCatalogCard.asp?PN=114681&B1=Display+Card

here is a hot street cam that works great in many 383 camaros with at least 10.5 static cpr with 3.5-4.1 gears
now the timeing is intake opens 29.0 btdc, closes 71.0 abdc exhaust opens 77.0 bbdc, closes 31.0 atdc so if we add the 29 to the 31 we get the overlap duration of 60 degs of which makes this cam fall in the center of HOT STREET

youll RARELY benefit from a single plane carb intake with a cam that has less than about 230 degs durration at .050 lift, below that a dual plane carb intake works better most of the time


header primary tube size should not greatly exceed the exhaust port size


http://www.slowgt.com/Calc2.htm#Header

http://victorylibrary.com/mopar/otto-c.htm
 

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grumpyvette ... You are the MAN!:hump:
This is cool stuff. I am amazed at how much has changed since the mid '80's when I was in the automotive game. I thought just the IT industry was the only one that changes constantly ... Wrong! :huh:
I see I have a lot of catching up to do.:whip: Oh well, beats watching TV:laughing:
Thanks for the post(s) ... good info!:thumbsup:
 

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some really great links here but so much of this is still hard for me to wrap my brain around.

I'm not sure if my lack of mechanical understanding is a limitation I put in my own mind, or if this stuff is just beyond my grasp.

I should have taken auto shop class instead of wood shop.:whip: thanks for taking the time to educate us.
 

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TOOOO much info... all great, but too much..thanks for taking the time to explain it all, it makes sence nonr the less.:smokin:
 

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mexvette said:
TOOOO much info... all great, but too much..thanks for taking the time to explain it all, it makes sence nonr the less.:smokin:
no such thing as too much info :)
 

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I agree also, there is absolutely no such thing as too much information when it comes to this particular subject. And from a man like GrumpyVette every syllable of it is worth reading. I've read some posts of his where I felt as if I was now inclined enough to build my own engine. That is one Digital Corvettes me member who can always hold my attention and appreciate the knowledge and people of this site.
 

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Augenstein doesn't know what he is talking about.

Setting the Record Straight on Torque and Power
- Thomas Barber​

Over the past decade, I have encountered any number of articles, on the Internet, that endeavor to explain torque and power. One of those articles, authored by a fellow named Bruce Augenstein, has appeared on dozens of independent Web sites, and seems to have had a strong influence on the popular understanding of this subject. Regardless of his intentions, his article has promoted several fallacious ideas, along with a dubious overall understanding of the subject. Before we look at what he wrote, it will be helpful for us to begin by identifying specific criteria that are useful in assessing the merit of his (or any other) effort to explain this subject:


  1. Foremost, the explanation should articulate the essential fact that acceleration at any time is proportional to power, along with the essential fact that the acceleration associated with any specific amount of engine torque, depends on the engine speed.
  2. Regardless of whether the explanation articulates those essential facts, it must not espouse any fallacious notions that are contrary to those facts.
  3. If the explanation endeavors to explain any fundamental physical concepts such as torque, work, and power, those explanations should be fundamentally correct.
Before looking at what he wrote, we should also take a quick review of the essential facts. If you turn the crank of a well to lift a 1-lb bucket at a steady rate of 1 ft/min, you are doing work at the rate of 1 ft-lb/min. This is simply the product of the force and the velocity, and turning it around, force is equal to power divided by the (non-zero) velocity. If you substitute that expression for force into the familiar equation that relates force, mass and acceleration, you get:

acceleration = power / (mass x velocity)

If you multiply the product of torque and rotational speed by twice pi, you effectively translate that product to the equivalent product of force and linear velocity, i.e., you calculate the power.

acceleration = engine_torque x 2 x pi x engine_speed / (velocity x mass)

Hence, given the vehicular velocity that is applicable to some point in time, the acceleration that you get, for a given amount of engine torque and a given mass, depends on the engine speed. Of course, if the ratio of engine speed to vehicle speed is given, as it effectively is while the gear ratio is held constant, acceleration will then vary according to the engine torque. Here we go:

“First of all, from a driver's perspective, torque, to use the vernacular, RULES :). Any given car, in any given gear, will accelerate at a rate that *exactly* matches its torque curve … Torque is the only thing that a driver feels, and horsepower is just sort of an esoteric measurement in that context. 300 foot pounds of torque will accelerate you just as hard at 2000 rpm as it would … at 4000 rpm in the same gear, yet … the horsepower would be *double* at 4000 rpm. Therefore, horsepower isn't particularly meaningful from a driver's perspective, and the two numbers only get friendly at 5252 rpm, where horsepower and torque always come out the same.

In contrast to a torque curve (and the matching pushback into your seat), horsepower rises rapidly with rpm. ... However, as I said, horsepower has nothing to do with what a driver *feels*.

You don't believe all this? Fine. Take your non turbo car (turbo lag muddles the results) to its torque peak in first gear, and punch it. Notice the belt in the back? Now take it to the power peak, and punch it. Notice that the belt in the back is a bit weaker? Fine. Can we go on, now? :)
It is true that 300 lb-ft of torque will yield the same acceleration at 2000 rpm as it will at 4000 rpm in the same gear, and the power will of course be double at 4000 rpm. However, the force that the driver feels at any instant is proportional to the driver’s acceleration, which is the same as the vehicular acceleration, and because vehicular acceleration is always proportional to power, it is obvious that the force felt by the driver at any instant is proportional to power. Yet, he asserts that “torque is the only thing that the driver feels”, that “horsepower is just sort of an esoteric measurement”, and that “horsepower has nothing to do with what a driver *feels*”. No honest, unbiased assessment of what he wrote could deny that the bulk and gist of it is simply nonsense. The only place where what he was thinking is uncertain, is where he says that torque and horsepower “get friendly at 5252 rpm”. It’s anyone’s guess what he was thinking when he wrote that, but the number 5252 is merely an artifact of using English units of measure for torque and power.

He argues that power is meaningless since according to him, the acceleration that you get for a given amount of engine torque is the same no matter the engine speed. That is what he encourages the reader to infer from the fact that, in a given gear, the acceleration that you get for a specific amount of engine torque does not vary. That is simply a ruse. The pertinent facts are that wheel torque at a given wheel speed depends equally on engine torque and engine speed, and that the acceleration associated with a given amount of engine torque always depends on the engine speed. These highly pertinent facts can be understood via the fact that power is the same at both locations (ignoring friction), and via the fact that power is essentially equal to the product of torque and rotational speed.

That excerpt came from his section titled, “The Case For Torque”, which took us right to the heart of the problem with his understanding of this subject. Near the beginning of his article, the section titled “Force, Work and Time”, offers this explanation of power:

If you have a one pound weight bolted to the floor, and try to lift it with one pound of force (or 10, or 50 pounds), you will have applied force and exerted energy, but no work will have been done. If you unbolt the weight, and apply a force sufficient to lift the weight one foot, then one foot pound of work will have been done. If that event takes a minute to accomplish, then you will be doing work at the rate of one foot pound per minute.
This explanation of power muddles the connection between power and acceleration, because it doesn’t reveal the meaning of instantaneous power, as distinct from that of average power, which has no simple relationship to instantaneous acceleration. Additionally, energy isn’t spent unless work is performed, and while a minimum force is required to overcome the force of gravity and move the weight at all, it makes no sense to talk of the force sufficient to move an object a specific distance. These misunderstandings clearly reveal a lack of basic knowledge, but they are innocent, and do not suggest any dubious agenda. However, smack dab in the middle of his theoretical explanation of power, he spiced things up a bit:

Now, it's important to understand that nobody on the planet ever actually measures horsepower from a running engine. What we actually measure (on a dynomometer) is torque, expressed in foot pounds (in the U.S.), and then we *calculate* actual horsepower by converting the twisting force of torque into the work units of horsepower.
Does this mean that power cannot be measured except by first measuring torque? Why else would this be “important to understand”, or worth mentioning? The notion, that power is somehow less real than torque, is easily identifiable as a theme of the article. Yet, it has no meaning or interpretation that can be confirmed experimentally, and as far as the orthodoxy and methodology of empirical science is concerned, notions of that sort are meaningless. This criticism would be no less valid even if it were true that power is only ever deduced by measuring torque and rotational speed. Of course, with inertial dynamometers, you can deduce power from the drum’s angular acceleration and its inertial moment, without measuring torque. For that matter, if you were to apply an engine to the task of lifting an elevator car and you inserted a continuously variable transmission between them to allow you to stabilize the speed of both the engine and the elevator car at any desired engine speed, you would then have a brake dynamometer of sorts. You would deduce power by multiplying the elevator’s steady velocity by its weight (minus the counter-weight), and as with brake dynamometers in general, that measurement will be unaffected by the engine’s inertial resistance to acceleration.

Next came the section I discussed first, and then a section titled, “The Case For Horsepower”:

OK. If torque is so all-fired important, why do we care about horsepower?
Because (to quote a friend), "It is better to make torque at high rpm than at low rpm, because you can take advantage of *gearing*.

For an extreme example of this, I'll … describe a waterwheel I got to watch awhile ago. This was a pretty massive wheel …, rotating lazily on a shaft which was connected to the works inside a flour mill. … the wheel typically generated about 2600(!) foot pounds of torque. …it was rotating at about 12 rpm. If we hooked that wheel to, say, the drivewheels of a car, that car would go from zero to twelve rpm in a flash, and the waterwheel would hardly notice :). … twelve rpm of the drivewheels is around one mph for the average car, and, in order to go faster, we'd need to gear it up. To get to 60 mph would require gearing the wheel up enough so that it would be effectively making a little over 43 foot pounds of torque at the output, which is not only a relatively small amount, it's less than what the average car would need in order to actually get to 60. Applying the conversion formula gives us the facts on this. Twelve times twenty six hundred, over five thousand two hundred fifty two gives us: 6 HP.

Oops. Now we see the rest of the story. While it's clearly true that the water wheel can exert a *bunch* of force, its *power* (ability to do work over time) is severely limited.
Even though there are no errors per se in this, I still find it annoying. He started by saying that we care about horsepower because making torque at higher rpm means that you can take advantage of gearing. The gist of the anecdote is that even though the torque of the waterwheel itself is substantial, if gearing is applied to increase the output speed, the torque is reduced accordingly. He didn’t say anything about why that happens. He produced a value for the output torque, without any explanation of how it was calculated. He calculated the power, but he did not mention that power, being the same at the output as it is at the input, explains why the output torque must decrease in order to compensate for the increase in output speed. At the end, the point of this anecdote seemed to be to reiterate the fact that torque by itself doesn’t determine the capacity to perform work over time. The formula that you use to calculate power from torque and rotational speed tells you that, and although that is certainly relevant, that fact by itself doesn’t shed much light on the connection between power and acceleration.

Next came the long section titled, “At the Dragstrip”, the essence of which is:

… some examples of how horsepower makes a major difference in how fast a car can accelerate, in spite of what torque on your backside tells you :). A very good example would be to compare the current LT1 Corvette with the last of the L98 Vettes, built in 1991. … The cars are geared identically …. First, each car will push you back in the seat … with the same authority - at least at or near peak torque in each gear. One will tend to *feel* about as fast as the other to the driver, but the LT1 will … be significantly faster than the L98, even though it won't pull any harder. …. Where the L98 has to shift to second (and throw away torque multiplication for speed), the LT1 still has around another 1000 rpm to go in first, and thus begins to widen its lead ...

Another example would be the LT1 against the ZR-1. Same deal, only in reverse. The ZR-1 actually pulls a little harder than the LT1... The real advantage, however, is that the ZR-1 has another 1500 rpm in hand at the point where the LT1 has to shift….There are numerous examples of this phenomenon. The Integra GS-R, for instance, is faster than the garden variety Integra, not because it pulls particularly harder (it doesn't), but because it pulls *longer*...
In this section, he argues that greater power can yet be advantageous because it allows the driver to wait longer before shifting to the next gear. He repeatedly asserts that greater power allows you to pull “longer”, but not “harder”. He consistently applied the constraint that the two cars that he was comparing in order to illustrate what he was trying to say, share identical transmissions and identical overall gear ratios. That constraint obscures the pertinent fact that the car with greater peak power may well exhibit greater peak wheel torque in each individual gear, even if its peak engine torque is less than that of the other vehicle. This section, which accounts for nearly half of the article, mistakenly assumes that the significance of power can be understood and explained by considering only the peak power. It then compounds that mistake by giving a ridiculous, bogus explanation of the advantage of greater peak power.

Toward the end of the article, in the section titled, “At The Bonneville Salt Flats”, he talked about the fact that the power peak is the best engine speed (regardless of the vehicle speed):

I know I said that acceleration follows the torque curve in any given gear, but if you factor in gearing vs car speed, the power peak is *it*. An example, yet again, of the LT1 Vette will illustrate this. If you take it up to its torque peak (3600 rpm) in a gear … However, if you re-gear the car so it is operating at the power peak (5000 rpm) *at the same car speed*, it will deliver more torque to the drive wheels, because you'll need to gear it up by nearly 39% (5000/3600), while engine torque has only dropped by a little over 7% (315/340). You'll net a 29% gain in drive wheel torque at the power peak vs the torque peak, at a given car speed.
Note first that it isn’t generally necessary to re-gear a car in order to select an engine speed at or near the power peak in lieu of the torque peak. Low vehicle speed, where 1st gear is the gear that offers the greatest power, is the exception of course.

That was the closest that he ever got to saying that acceleration is proportional to power. It is in the vicinity of the target, but because it deals specifically with the power peak and does not say plainly that acceleration is proportional to power, it doesn’t hit the bulls-eye. Without a clear understanding of the fact that acceleration is always proportional to power, there is no understanding of why optimal shifting consists of always selecting the gear that yields the greatest power. Note also that even though his calculation correctly implies that wheel torque is proportional to the product of engine torque and engine speed (and thus to power), he never plainly said so, and he never said anything about why it is true.

For his summary, he chose to repeat his perspective on why power is relevant:

The Only Thing You Really Need to Know

Repeat after me. "It is better to make torque at high rpm than at low rpm, because you can take advantage of *gearing*." :)
This is not particularly conducive to an insightful understanding of why power and engine speed matter. Engine torque reveals the amount of work performed over any specific interval of crankshaft rotation, whereas acceleration at any time is proportional to the rate at which work is being performed, which rate depends as much on engine speed as it depends on engine torque.

The facts that are pertinent to a proper understanding of this subject are conspicuously missing from Augenstein’s article, having been replaced by bogus ideas. Instead of saying plainly that acceleration is proportional to power, he defiantly asserted that only engine torque has anything to do with what a driver feels. He made audacious claims about the measurability of power, and his explanations of the significance of power, were bogus. There is very little in his article that qualifies as a usefully correct explanation of anything, and most of what he espouses is bogus.
 
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