Camshaft Lobe Separation Angle: What Does it Mean?

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camshaft lobe

The lobe separation angle of a camshaft is often determined by the engine’s purpose, its displacement and its compression ratio. A 350cu in oval track racing engine, for example, often runs on a narrow lobe separation angle of 106 degrees. In contrast, a smooth-running performance street engine might use a lobe separation angle of 112 to 114 degrees. Five-hundred cubic inch NHRA Pro Stock engines that rev to 11,000rpm operate on 116 degrees and 800-plus cu in Pro Stock Mountain Motors 120 to 122.

lobe angles

The lobe separation angle or LSA is the angle in camshaft degrees between the maximum lift points, or centerlines, of the intake and exhaust lobes. The lobe separation angle or LSA is the angle in camshaft degrees between the maximum lift points, or centerlines, of the intake and exhaust lobes. It affects the amount of valve overlap; that is the brief period of time when both the intake and exhaust valves are open.

A narrower LSA adopts more overlap and with it a lumpier idle and a narrower more specific power band. The narrower separation makes the engine sound choppier. Some engine specialists refer to it as that 106 sound—the NASCAR Cup and short track oval sound where lobe separation is set at 106 degrees. Its primary influence is to impel urgent acceleration off the turns when the throttle is opened.

A wider LSA, on the other hand, reduces valve overlap, offering better idle and cruising qualities. Supercharged engines typically benefit from a wider LSA because they don’t require as much overlap for exhaust scavenging as does the naturally aspirated engine.

Doug Patton, Pro Line Racing Engines

Doug Patton, Pro Line Racing Engines

“Changing the lobe separation angle,” says Doug Patton of Pro Line Race Engines, “changes the amount of overlap that exists during the time the intake and exhaust valves are both open. On a naturally aspirated engine, the lobe separation angle has an effect on whether the engine reaches peak torque a little earlier or later in the rpm range. Typically, narrower lobe separation develops peak torque at lower rpm and widening the separation tends to build peak torque higher in the rpm range. Nitrous engines, which make plenty of power and torque, often run wide lobe separation angles to moderate cylinder pressures and temperatures.

“Lobe separation angles,” he continues, “are influenced by the camshaft grind. If a street car has smaller lift (the amount the valve lifts off its valve seat) and duration numbers (the degrees of crankshaft rotation for which the valve is held open) they might run 112 or 114. Widening their separation angle helps increase upper rpm power output. Alternatively, if you are running a bigger camshaft to gain maximum top-end power, cam makers often suggest reducing the lobe separation angle to recover power lost in the lower rev range.”

Chuck Lawrence, Jon Kaase Racing Engineswidth=

Chuck Lawrence, Jon Kaase Racing Engines

Tellingly, when engine builder Chuck Lawrence received the order to bestow a 520cu in big-block Ford with the sound of a Pro Stock engine, he replaced the normal 112LSA hydraulic roller cam with one of 108LSA. “The result sounded wonderful,” said Mr. Lawrence, “but it didn’t rev as enthusiastically and it made 30hp less than normal!”

“If you changed the lobe separation of a street engine from 112 degrees to 106 and didn’t do anything else,” says Jon Kaase, “the engine would idle a lot rougher and generate worse exhaust emissions largely because of unburned fuel.”

In conclusion, lobe separation angles change the amount of valve overlap, which affects many performance factors particularly idle quality, peak torque that can be moved from a lower rev range to a higher range and power bands that can be narrowed or broadened.

Source:

  • Erson Cams,
  • Moore Good Ink
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17 Responses to “Camshaft Lobe Separation Angle: What Does it Mean?”
  1. Frederic

    It can change just about every aspcet of the motors running. It can give you a lopey idle, allow the motor to rev up quicker, and change the amount of air used, changing the exhaust note, among other things. Since the exhaust note is the sound of combustion happening inside the chamber, any change to the state of that combustion will produce an audible result. Generally a rough, loping idle is considered tough sounding, this type of idle is normally atributed to a high duration camshaft.

    Reply
  2. Clarence

    “Changing the lobe separation angle,” says Doug Patton of Pro Line Race Engines, “changes the amount of overlap that exists during the time the intake and exhaust valves are both open. On a naturally aspirated engine, the lobe separation angle has an effect on whether the engine reaches peak torque a little earlier or later in the rpm range. Typically, narrower lobe separation develops peak torque at lower rpm and widening the separation tends to build peak torque higher in the rpm range. Nitrous engines, which make plenty of power and torque, often run wide lobe separation angles to moderate cylinder pressures and temperatures.” This paragraph is incorrect. Narrow lobe separation makes for more low end torque at a lower engine speed. I am sure that the writer or/and the speaker realized that. Either a misspeak or a typo.

    Reply
  3. Clarence

    “Changing the lobe separation angle,” says Doug Patton of Pro Line Race Engines, “changes the amount of overlap that exists during the time the intake and exhaust valves are both open. On a naturally aspirated engine, the lobe separation angle has an effect on whether the engine reaches peak torque a little earlier or later in the rpm range. Typically, narrower lobe separation develops peak torque at lower rpm and widening the separation tends to build peak torque higher in the rpm range. Nitrous engines, which make plenty of power and torque, often run wide lobe separation angles to moderate cylinder pressures and temperatures.” This paragraph is incorrect.To correct my first post: Narrow lobe separation doesn’t make for more low end torque at a lower engine speed. It is the exact opposite .I am sure that the writer or/and the speaker realized that. Either a misspeak or a typo. (And I did it on my first post! )

    Reply
    • Customer Service

      Hi, Clarence. We would like to let you know that your feedback has been forwarded to the proper department; your comments are important to us and help with the development of our online video streaming community.

      Reply
    • jonesboys

      ‬ So if I hear this correctly a cam with a larger degree of sepertion has more lope or sounds like a old Harley at slow idle? So does this effect lift on camshaft?

      Reply
      • Customer Service

        Hello. Lobe separation does not affect the amount of lift that is ground into the camshaft profile.
        Thanks
        Mark-Classic Car Restoration Club

        Reply
  4. pweaver

    I’ve got an Oldsmobile motor installed for marine use with a roller cam and in this application the headers are water cooled by spraying water into the headers a couple inches from the exhaust port. The problem is the engine sucks water in from the exhaust into the cylinders and ends up with water in the oil. I’ve done a lot of experimentation to prove this is what’s happening. I was told a wider lobe separation angle would resolve this problem since the exhaust won’t “see” as much of the intake vacuum. Is this true? Please advise. Thanks
    Paul

    Reply
    • Customer Service

      Hello. Sorry I am not a marine expert, but there is no engine vacuum on the exhaust side of the of the engine.
      The vacuum is created on the intake side only. I don’t believe your issue is related to cam lobe separation.
      Thanks
      Mark-Classic Car Restoration Club

      Reply
  5. Ed Rufle

    I was just discussing with my son the reason why Pontiac used a VERY conservative cam in the 350 it put in the 74 GTO option. The engine as I recall had 7.6 to 1 mechanical compression. Why? I suspect because it raised the working compression and with its four barrel carburetor gave the car 200+ hp. That doesn’t sound like much but with a manual transmission the actually ran pretty decent. My point was GM had a lot of red tape to work around to get emissions and mpgs demands. Of course, when Chevy cam out with the LS1 it was clear this kind of thinking led to a stock cam with an LSA of 122+ which seemed just as strange to me as a duration (?) of 169 on a sport model. But I think they were fighting the same battle but Pontiac, who new hiw to build engines with horsepower, just didn’t have the technology in 1974.

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  6. Doug

    I’m so confused! Cam tech has always been a foreign language for me and between the article and the first comment and then the corrected one, I’m worse off now than before. I gather that a narrow LSA produces a rougher idle; now, does it produce more or less torque in the lower to mid range RPM scale? Also, the article mentioned cam degrees, I can’t get my head around that term as the shaft makes a complete turn of 360 degrees therefore the lobe must also travel 360 degrees. I realize a lifter riding the lobe travels a greater distance but how does that affect cam degrees, and wouldn’t that change with the design of the lobe? As I said, “I’m so confused!”

    Reply
    • Customer Service

      Hi Doug. Sorry for all of the confusion, A narrower LSA will produce more torque at lower/mid RPMs, As it relates to this article, Cam degrees are the number of degrees of lobe separation between the intake and exhaust maximum opening. On cams with narrow LSA there are times when both the intake and exhaust valves are open. The lobes on the cam are cut to determine: how quickly a valve opens, how long it remains open, how far open the valve becomes and how quickly it closes. The size of the cam lobes does not affect the degrees of cam lobe separation though, although it can factor into the amount of overlap. And you are correct there are 360 degrees of total rotation, that is a constant.
      Thanks
      Mark-Classic Car Restoration Club

      Reply
  7. John E.

    Can someone tell me definitively which of the two differing comments on the effect of lobe seperation (overlap) on engine torque and idle is absolutely correct.

    Reply
    • Customer Service

      Dear John,

      Thank you for your patience.

      Simply put, tighter lobe separation angles (LSA) create greater low end torque, rougher idle and less engine vacuum.

      Wrench Safe
      Mark
      Classic Car Restoration Club Video membership

      Reply