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Stock Rocker Tech!
05-09-2011, 09:05 AM
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Staging Lane
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Join Date: May 2011
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Stock Rocker Tech! I found some info on stock rockers after doing some research for myself and i thought i would share it with u all. So here goes:
Gm ls engines come with roller fulcrum rocker arms with finger follower tips that actuate the intake and exhaust valves.
The finger follower design is designed to roll and slide across the tip of the valve much like arched runners on a rocking chair. Anything mechanical has a limit. The oe 1.7 ratio rockers arms were designed to be used with moderate cams with less then .550-inch lift and v-springs designed for 100k warranties.
Running high lift cams with o.e roickers:
When you go greater then .550-inch lift and v-springs that are very stiff you could end up with:
1.Pitted,Galled or destroyed valve tips
2.Blued rocker tips
3.Worn/destroyed fulcrum bearings
4.V-spring failure
5.V-stem failures
6.Worn v-guide inserts
Rocker arm types:
1.Full arc: Most roller tip rockers have a full arc rocker motion.
The roller tip is to be centered on the tip of the valve as much as possible through the motion of the rockers lift. Keeping th load centered on the tip of the valve reduces the amount of foward and back load on the v-guide.
2.Partial arc: Gm ls 1.7 rocker arms are considered a partial arc finger follower rocker arm because of the way they contact the valve tip. The arc that is on the tip of the ls rocker is a cam itself. When the rocker arm moves the valve the arc on the tip acts as a wedge to push the valve down. The ls series rocker is designed to start at the inboard edge of the valve tip then rolls and slides across the valve tip during lift to the outer edge of the v-tip. This type of rocker arm motion tends to load the v-guide to 1 side throughout the lift cycle to about .550-inch.
Gm ls series rocker arms at .550-inch run out of arc on the valve tip and start to jamb and nose dive. This causes most valvetrain issues and shimming the rocker arm up limits youre lift even more and increases contact stress to the v-tip and tip of the rocker.
Valve guide materials:
1.Powder metel v-guides made up of iron,carbon,copper,and other elements those three being the main elements. They are impreganted with oil and some dry lubes. So basically all the good lubricating elements that have been taken out of the oil are put into the componets. Bronze v-guides do not have strength to support a ls series rocker loads that would be put on it during valve events.
Valve spring:
1.When high rate v-springs are put on a head it increases the amount of stress put on the v-train. Four hundred pound open force springs are the safe limit foe the o.e ls rocker arm body.
Conclusion:
1.If a ls cylinder head has bronze alloy v-guides roller tip rockers should be used to reduce load on the v-guide.
2.If bronze alloy v-guides are used with o.e ls rocker arms they will fail causing the engine to use oil.
3.Powered metel v-guides should be used if you are going to use o.e ls rocker arms and limit cam lift to .550-inch or less. The mass of the v-train componets should be kept to a minimum but not to sacrifice reliability.
All this info came from these respected authors.
: Trick flow specialties.
: G.M high tech performance.
Gm ls engines come with roller fulcrum rocker arms with finger follower tips that actuate the intake and exhaust valves.
The finger follower design is designed to roll and slide across the tip of the valve much like arched runners on a rocking chair. Anything mechanical has a limit. The oe 1.7 ratio rockers arms were designed to be used with moderate cams with less then .550-inch lift and v-springs designed for 100k warranties.
Running high lift cams with o.e roickers:
When you go greater then .550-inch lift and v-springs that are very stiff you could end up with:
1.Pitted,Galled or destroyed valve tips
2.Blued rocker tips
3.Worn/destroyed fulcrum bearings
4.V-spring failure
5.V-stem failures
6.Worn v-guide inserts
Rocker arm types:
1.Full arc: Most roller tip rockers have a full arc rocker motion.
The roller tip is to be centered on the tip of the valve as much as possible through the motion of the rockers lift. Keeping th load centered on the tip of the valve reduces the amount of foward and back load on the v-guide.
2.Partial arc: Gm ls 1.7 rocker arms are considered a partial arc finger follower rocker arm because of the way they contact the valve tip. The arc that is on the tip of the ls rocker is a cam itself. When the rocker arm moves the valve the arc on the tip acts as a wedge to push the valve down. The ls series rocker is designed to start at the inboard edge of the valve tip then rolls and slides across the valve tip during lift to the outer edge of the v-tip. This type of rocker arm motion tends to load the v-guide to 1 side throughout the lift cycle to about .550-inch.
Gm ls series rocker arms at .550-inch run out of arc on the valve tip and start to jamb and nose dive. This causes most valvetrain issues and shimming the rocker arm up limits youre lift even more and increases contact stress to the v-tip and tip of the rocker.
Valve guide materials:
1.Powder metel v-guides made up of iron,carbon,copper,and other elements those three being the main elements. They are impreganted with oil and some dry lubes. So basically all the good lubricating elements that have been taken out of the oil are put into the componets. Bronze v-guides do not have strength to support a ls series rocker loads that would be put on it during valve events.
Valve spring:
1.When high rate v-springs are put on a head it increases the amount of stress put on the v-train. Four hundred pound open force springs are the safe limit foe the o.e ls rocker arm body.
Conclusion:
1.If a ls cylinder head has bronze alloy v-guides roller tip rockers should be used to reduce load on the v-guide.
2.If bronze alloy v-guides are used with o.e ls rocker arms they will fail causing the engine to use oil.
3.Powered metel v-guides should be used if you are going to use o.e ls rocker arms and limit cam lift to .550-inch or less. The mass of the v-train componets should be kept to a minimum but not to sacrifice reliability.
All this info came from these respected authors.
: Trick flow specialties.
: G.M high tech performance.
Last edited by Bloombox1; 05-09-2011 at 09:29 AM. Reason: more info
