I need to know about cams.

Unit 5302 · 01-07-2002, 01:47 AM

Lift: The lift given is generally listed with the rocker ratio included. Rockers have a ratio of like 1.6:1 or 1.7:1 which increases the cam lift. Most cams are rated with 1.6:1 rockers for the Mustang.

Duration: 224*/224*@.500 means the exhaust valve is open for 224* of rotation at .500 lift. @.500 is the most common duration measurement cited. There is also say 282*/282* which would be overall duration.

Split Duration: means the intake duration and exhuast duration is different. Since most Ford heads are a little weak on the exhaust port, getting a split duration cam can make up for that by favoring the exhaust side. IE 220*/224*@.500

LSA: Lobe seperation angle. A wider lobe seperation angle indicates you'll retain more cylinder pressure. The smaller the lobe seperation angle, the less vacuum and cylinder pressure then engine will have.

Now, how they work.

If you have a long duration camshaft, the additional time the valves are open will increase the flow efficiently, but because of the greater duration, they will generally have a small LSA and when you get too big (at that point you'll have a race engine) the car won't want to idle and you'll have very poor vacuum forcing you to drop power brakes, etc.

Going high lift enables you to flow more without necessarily increasing duration. That means you can keep low end power/drivability while making more hp. The drawback to this is obvious. You're wasting a ton of hp lifting the valve way up. The more you lift, the stronger your valvetrain has to be, and the more friction and power drain you'll have.

Roller vs Non Roller: A roller cam/lifter uses a roller on the pushrod to decrease friction and pushrod side loads. With a non roller cam, a steep lift will be limited because you can potentially break parts.

Hydraulic vs Solid: A hydraulic lifter cam uses oil to assist the lifter in lifting the valves. They do not require adjustment like solid lifter cams, and because of that they are generally quieter (as long as you have oil pressure, hehe). They make for a smoother valvetrain, and ease the load on the valvetrain to make for a more efficient setup. The drawback is that at higher rpms the lifters have trouble "pumping up" or in other words, retaining oil in them keeping them from completely dropping down. That causes the valves to stay open longer and you lose your top end power because of the extreme loss of cylinder pressure. That generally takes place beyond about 7000rpms on a well put together engine. When you really rev a hydrualic engine, you need SERIOUS valve springs to force everything closed. Stock valvesprings/lifters can start to fail before redline when they are old.

Hope that helps a little.

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01-07-2002, 01:47 AM	#2
Unit 5302 Registered Member Join Date: May 1999 Posts: 5,246	Lift: The lift given is generally listed with the rocker ratio included. Rockers have a ratio of like 1.6:1 or 1.7:1 which increases the cam lift. Most cams are rated with 1.6:1 rockers for the Mustang. Duration: 224/224@.500 means the exhaust valve is open for 224* of rotation at .500 lift. @.500 is the most common duration measurement cited. There is also say 282/282 which would be overall duration. Split Duration: means the intake duration and exhuast duration is different. Since most Ford heads are a little weak on the exhaust port, getting a split duration cam can make up for that by favoring the exhaust side. IE 220/224@.500 LSA: Lobe seperation angle. A wider lobe seperation angle indicates you'll retain more cylinder pressure. The smaller the lobe seperation angle, the less vacuum and cylinder pressure then engine will have. Now, how they work. If you have a long duration camshaft, the additional time the valves are open will increase the flow efficiently, but because of the greater duration, they will generally have a small LSA and when you get too big (at that point you'll have a race engine) the car won't want to idle and you'll have very poor vacuum forcing you to drop power brakes, etc. Going high lift enables you to flow more without necessarily increasing duration. That means you can keep low end power/drivability while making more hp. The drawback to this is obvious. You're wasting a ton of hp lifting the valve way up. The more you lift, the stronger your valvetrain has to be, and the more friction and power drain you'll have. Roller vs Non Roller: A roller cam/lifter uses a roller on the pushrod to decrease friction and pushrod side loads. With a non roller cam, a steep lift will be limited because you can potentially break parts. Hydraulic vs Solid: A hydraulic lifter cam uses oil to assist the lifter in lifting the valves. They do not require adjustment like solid lifter cams, and because of that they are generally quieter (as long as you have oil pressure, hehe). They make for a smoother valvetrain, and ease the load on the valvetrain to make for a more efficient setup. The drawback is that at higher rpms the lifters have trouble "pumping up" or in other words, retaining oil in them keeping them from completely dropping down. That causes the valves to stay open longer and you lose your top end power because of the extreme loss of cylinder pressure. That generally takes place beyond about 7000rpms on a well put together engine. When you really rev a hydrualic engine, you need SERIOUS valve springs to force everything closed. Stock valvesprings/lifters can start to fail before redline when they are old. Hope that helps a little.