Ever wonder what is actually working to get the air charge into the combustion chamber? This little miracle of engineering is called a camshaft. It causes the valves to open and close in a timed manner that makes the internal combustion engine a reality. Now-a -days,factory grinds are a very well engineered to gibe a good compromise for low end torque,drivability, durability and fuel economy.And then there's the smooth idle that comes along with that.
Have you ever heard the expression that "It's all in the Cam and the heads?" Well,to a certain extent that is true. However,most engine builders build the bottom end of the engine to allow for more aggressiveness from the top end of the motor.Performance camshafts like Competition Cams Hi-Energy Camshafts
& Edelbrock Power Packages like Edelbrock 2099 Power Package and Edelbrock 2098 Power Package Kit
are designed to make big horsepower gains just by themselves. Now,think about this for a minute. If there is more vacuum to pull the air charge into the cylinder and higher compression pistons to compress the air-fuel mixture more effectively then you are going to produce even more power.This is why a decent engine builder will always build the bottom end of the motor as well but,more on that later.
You have a few things to consider when deciding what type of camshaft you would like to install and keep in mind the this is a fairly complicated undertaking so you want to get it right the first time.
Flat or Roller Tappet
Flat tappet cams use a flat bottom lifter and Roller cams use a roller lifter. Now for obvious reason the roller is generally the better choice. Less wear,less friction and smoother operation inside the top end. Most newer Chevy engines use a roller cam from the factory. That's not to say that a flat tappet cam will not suit your needs but, in my opinion a roller is the way to go. There is also the choice of solid lifter or hydraulic lifter. The difference between the two are a solid lifter is solid through out and a hydraulic has a small piston like set up that pressures up. The hydraulic lifter does this to help accommodate for engine temperatures.
Have you ever heard the expression that "It's all in the Cam and the heads?" Well,to a certain extent that is true. However,most engine builders build the bottom end of the engine to allow for more aggressiveness from the top end of the motor.Performance camshafts like Competition Cams Hi-Energy Camshafts
& Edelbrock Power Packages like Edelbrock 2099 Power Package and Edelbrock 2098 Power Package Kit are designed to make big horsepower gains just by themselves. Now,think about this for a minute. If there is more vacuum to pull the air charge into the cylinder and higher compression pistons to compress the air-fuel mixture more effectively then you are going to produce even more power.This is why a decent engine builder will always build the bottom end of the motor as well but,more on that later.You have a few things to consider when deciding what type of camshaft you would like to install and keep in mind the this is a fairly complicated undertaking so you want to get it right the first time.
Flat or Roller Tappet
Flat tappet cams use a flat bottom lifter and Roller cams use a roller lifter. Now for obvious reason the roller is generally the better choice. Less wear,less friction and smoother operation inside the top end. Most newer Chevy engines use a roller cam from the factory. That's not to say that a flat tappet cam will not suit your needs but, in my opinion a roller is the way to go. There is also the choice of solid lifter or hydraulic lifter. The difference between the two are a solid lifter is solid through out and a hydraulic has a small piston like set up that pressures up. The hydraulic lifter does this to help accommodate for engine temperatures.
When you talk about a "cam" with most hot rodders one of the first things you're going to hear about is lift.
Lift is basically how much the cam will open the valve. If a cam creates a .454" lift and you have 1.5 ratio rocker arms then the initial cam lift is .302". Now if you have 1.6 ratio rockers then your total lift will be .483"with the same cam shaft.Now for the most part,I'm not going to get real technical just for the simple reason is,most of us are just interested in whether or not a particular cam profile will work for them or not.Now keep in mind most stock springs will accommodate a camshaft that is slightly bigger than stock. Anything more and stronger springs will be required like Competition Cams 93816 Valve Springs.
Duration of lift
Generally this term is just referred to as duration. Duration is how long the valve is open inside the combustion chamber. The value will open gradually and reach a peak in the center of the cam lobes duration. Different cam manufactures may use different standards for measuring duration. Some like Competition Cams
may use .006 and another like Crane Cams
will use .004. This means that that is where they start to measure when the lifter starts to open the valve. Now,most people will use the number .050 inch tappet lift when they advertise duration simply because it's a common ground. Camshafts with different durations between their intake and exhaust figures are called dual pattern cams.
may use .006 and another like Crane Cams will use .004. This means that that is where they start to measure when the lifter starts to open the valve. Now,most people will use the number .050 inch tappet lift when they advertise duration simply because it's a common ground. Camshafts with different durations between their intake and exhaust figures are called dual pattern cams.
Camshaft Centerlines
Now here is where things will get a little more technical but,with a little patience and understanding we'll get through this and hopefully be better for it.
Your camshaft centerline refers to the middle or the duration curve. This is very important in terms of timing. To figure out where the camshaft is in relation to the crank shaft we used the lobe centerline of #1 intake. When the #1 piston is at TDC,that is the start of the intake phase of the cylinder.Camshaft centerline are generally designed to be anywhere from .106 and around .114 degrees ATDC,some may be .116 degrees ATDC. The difference between the intake and exhaust centerlines is call lobe separation . Now,baring in mind that no matter what you will always have a certain amount of time when both valves are open at once. This is called valve overlap. Have a look at the picture and you'll get a basic idea.
Now you can figure out the lobe separation angle by adding the intake centerline and the exhaust centerline together,factor in the fact the cam spins at half the crankshaft speed so that means you will divide the added numbers by 2. Intake centerline .108,exhaust centerline .122. So .108 + .122 / 2 = .115 lobe separation.
Now,valve overlap as mentioned above is the time that both valves are open at the same time. Here's a little something from personal experience. The Tuned Port Injection
on the third gen Camaros of the late 80's took advantage of what is referred to as the intake pulse. This was simply due to the length of the runner and how it worked in relation to how the air charge went into the cylinder. The reason it worked so well is because of the valve overlap. At higher engine speeds this created an environment where the escaping exhaust gases actually helped pull the incoming air charge into the cylinder more effectively. Now I'm not sure if that was the intented idea behind the design or if it was stumbled on by mistake. Non the less it works. Now increasing or decreasing your valve over lap can have a huge impact on how your engine performs. In a nutshell,increased over lap helps the engine produce more power higher up in the RPM range and decreased works the same for lower RPM,theoretically. Bare in mind that increasing lift will increase overlap,Now depending on your advance you don't want a small lobe separation angle because you may run into a little thing called reversion. Reversion refers to a situation where the exhaust pulse momentarily flows backwards during the overlap phase.
I hope this information helps, I used a few references off the net and a couple from books like the ones found here.
Good luck with your build up.
Now,valve overlap as mentioned above is the time that both valves are open at the same time. Here's a little something from personal experience. The Tuned Port Injection
on the third gen Camaros of the late 80's took advantage of what is referred to as the intake pulse. This was simply due to the length of the runner and how it worked in relation to how the air charge went into the cylinder. The reason it worked so well is because of the valve overlap. At higher engine speeds this created an environment where the escaping exhaust gases actually helped pull the incoming air charge into the cylinder more effectively. Now I'm not sure if that was the intented idea behind the design or if it was stumbled on by mistake. Non the less it works. Now increasing or decreasing your valve over lap can have a huge impact on how your engine performs. In a nutshell,increased over lap helps the engine produce more power higher up in the RPM range and decreased works the same for lower RPM,theoretically. Bare in mind that increasing lift will increase overlap,Now depending on your advance you don't want a small lobe separation angle because you may run into a little thing called reversion. Reversion refers to a situation where the exhaust pulse momentarily flows backwards during the overlap phase.I hope this information helps, I used a few references off the net and a couple from books like the ones found here.
Good luck with your build up.
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