What is lifter pre-load?
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From: azle texas
What is lifter pre-load?
I just purchased a set of roller rockers from crane to put on my 351w. The instructions mention a preload setting torque of 18-20 ft/lbs. The instruction sheet is sort of confusing I will most likely have to call Crane later today. If anyone has any tips on installing roller rockers-thats cool.
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It's just the rocker adjustment. When they say 18-20 ft-lb's then it must be for pedalstal mount rockers. With pedalstal mount rockers, you just tighten them down to the tourqe spec. If it's too tight, then you need shims, but it's probably okay.
You can check to see if not too tight, by seeing if you can barely spin them with your fingers (with a no lift point on the cam) after they have been cycled through a few times.
With adjustable stud mount rockers you tighten them (at a no lift point in the cam cycle) untill you just can't spin them with your fingers, then an additional 3/4 turn.
You can check to see if not too tight, by seeing if you can barely spin them with your fingers (with a no lift point on the cam) after they have been cycled through a few times.
With adjustable stud mount rockers you tighten them (at a no lift point in the cam cycle) untill you just can't spin them with your fingers, then an additional 3/4 turn.
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From: azle texas
Originally Posted by P51D Mustang
It's just the rocker adjustment. When they say 18-20 ft-lb's then it must be for pedalstal mount rockers. With pedalstal mount rockers, you just tighten them down to the tourqe spec. If it's too tight, then you need shims, but it's probably okay.
You can check to see if not too tight, by seeing if you can barely spin them with your fingers (with a no lift point on the cam) after they have been cycled through a few times.
With adjustable stud mount rockers you tighten them (at a no lift point in the cam cycle) untill you just can't spin them with your fingers, then an additional 3/4 turn.
You can check to see if not too tight, by seeing if you can barely spin them with your fingers (with a no lift point on the cam) after they have been cycled through a few times.
With adjustable stud mount rockers you tighten them (at a no lift point in the cam cycle) untill you just can't spin them with your fingers, then an additional 3/4 turn.
If the push rods turn fairly easy should I give them a little more torque? Torqued em to 19ft/lbs
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No, the rocker is probably as tight as it can get, with the pedalstal base tight against the head. The tourqe amount is actually the amount of metal stretch on the bolt.
I'm pretty sure your just right. It's getting the lifter pre-load too tight that can be the real danger, as this can prevent the valves from closing completely, quickly causing burnt valves. After the engine has been turned over a few times, the lifters will bleed off some oil and the pushrods may spin rather freely. This is okay.
Roller rockers will not be 100% noise free. You will hear a little more valve train "chatter", compared to regular rockers, but that's normal.
Just a FYI point that you probably know, but just in case: Bolts should be tourqed with oil on the threads, never dry.
I'm pretty sure your just right. It's getting the lifter pre-load too tight that can be the real danger, as this can prevent the valves from closing completely, quickly causing burnt valves. After the engine has been turned over a few times, the lifters will bleed off some oil and the pushrods may spin rather freely. This is okay.
Roller rockers will not be 100% noise free. You will hear a little more valve train "chatter", compared to regular rockers, but that's normal.
Just a FYI point that you probably know, but just in case: Bolts should be tourqed with oil on the threads, never dry.
Last edited by P51D Mustang; Oct 1, 2006 at 09:37 PM.
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From: Erie PA
<TABLE cellSpacing=0 cellPadding=0 width="100%" border=0><TBODY><TR><TD width="100%"></TD><TD vAlign=top noWrap>
</TD></TR><TR><TD colSpan=2><HR></TD></TR><TR><TD colSpan=2>http://www.cranecams.com/?show=faq&id=3
Lifters (Hydraulic)
Hydraulic lifters have been the choice of the automotive industry for many years for several good reasons. when compared to a mechanical lifter, the hydraulics are:
1. Quieter.
2. Low maintenance.
3. An ability to adjust for thermal expansion of the engine.
4. Built in shock absorber, eases stress on valve train.
5. “Bleed Rate” can be designed to accommodate different engine RPM ranges.
Today’s modern engines all use either the standard design hydraulic lifter or the new low friction, high performance hydraulic roller design. Hydraulic lifters are the best for street applications, high performance, and mild racing applications where low maintenance is a primary concern.
What is the difference in the design of a Hydraulic and Mechanical Lifter?
Basically, the hydraulic lifter pushrod seat is moveable, the mechanical lifter seat is not. Both lifter types look the same from the outside, with both having pushrod seats held in by a retaining lock. The pushrod seat in a mechanical lifter usually registers upon an internal step inside the lifter body preventing it from moving (thus it gets the nickname “Solid Lifter”). What’s below the pushrod seat in the hydraulic lifter is a different story. Its pushrod seat is not restricted by a step, but instead sits on top of a moveable hydraulic mechanism which acts like a tiny hydraulic pump. Below this mechanism is valving and a spring to produce an upward force, moving the pushrod seat upward against the retaining lock.
What is Hydraulic Lifter Preload?
Mechanical cam designs require a running clearance or valve lash; hydraulic lifters are just the opposite. When the rocker arm assembly is properly torqued down into position, the pushrod must take up all the clearance and descend into the hydraulic lifter, causing the pushrod seat to move down by .020” to .060”. The distance that the pushrod seat moves down away from the retaining lock is the “Lifter Preload”. The hydraulic mechanism requires this precise amount of “preload” for it to do its job properly.
What happens if the amount of Hydraulic Lifter Preload is wrong?
If clearance exists between the pushrod and the seat in the hydraulic lifter, after the rocker arm assembly has been torqued down, you will have no lifter preload. In this case the valve train will be noisy when the engine is running. All of the hydraulic force produced by the lifter will be exerted against the lifter’s retaining lock, and this could cause the lock to fail.
If the opposite occurs and the pushrod descends too far (more than .060”), then you have excessive lifter preload. In theory, a hydraulic lifter can pump up whatever preload you put into it, therefore with excessive preload, as the engine RPM and oil pressure increases, the hydraulic mechanism will pump-up the pushrod seat. This will cause the valve to be open longer and lift higher. This will decrease the cylinder pressure, lowering the performance of the engine. If the preload is excessive it may cause “backfiring” from the engine. How to correct this situation will be explained in the next sections.
When rebuilding an engine, what can cause Lifter Preload to change?
Almost anything can affect lifter preload. If you do a valve job, surface the block or heads, change the head gasket thickness, or buy a new camshaft, the amount of preload can be affected. Sometimes these changes cancel one another out and your preload stays the same; this is more by luck than design. This is why you must always inspect the amount of preload the lifter has when reassembling the engine and be sure it is correct.
Fast and Easy Way to Check Hydraulic Lifter Preload when using Non-Adjustable Rocker Arms
With the cam, hydraulic lifters and pushrods in place, install your rocker arm assembly. Use the prescribed method in your repair manual and torque down all the valve train bolts in the proper sequence. Pick a cylinder that you are going to check. Hand rotate the engine in its normal direction of rotation until both valves are closed. You are on the compression cycle for that cylinder. (At this position the valve springs are at their least amount of tension making the job a little easier to do.)
Wait a few minutes, allowing the lifters to bleed down. Now, lay a rigid straightedge across the cylinder head, supporting it on the surface of the head where the valve cover gasket would go. Using a metal scribe and the straightedge, carefully scribe a line on both pushrods. Now carefully remove the torque from all valve train bolts, removing any pressure from the pushrods. Wait a few minutes for the pushrod seat in the hydraulic lifter to move back to the neutral position. Carefully scribe a new line on both pushrods.
Measure the distance between the two scribe marks, it represents the amount of lifter preload. If the lines are .020” to .060” apart you have proper lifter preload. If the lines are the same or less than .020” apart you have no or insufficient preload. If the lines are further apart than 060” you have excessive lifter preload. To bring your preload into tolerance, use one of the methods described in the next section if necessary, or call the Crane Tech Line for assistance (386/258-6174).
Methods to Adjust for Proper Hydraulic Lifter Preload
There are several different methods for increasing or decreasing the amount of lifter preload, depending on valve train design and how the rocker arm is held onto the cylinder head. Keep in mind that the automotive manufacturers have made changes to the valve train over the years. What may work on one year’s engine may not work for another, even though they are basically the same engine. There is one method that universally works on all these engines, change the pushrod length! Use a longer pushrod to increase preload, a shorter to reduce preload. Crane offers various length pushrods and offers custom length pushrods also.
Using Adjustable Rocker Arms to set Hydraulic Lifter Preload
The easiest method to arrive at proper lifter preload is when you have an engine with “Adjustable Valve Train”. Unfortunately, since 1967 most domestic engines, with the exception of small and big block Chevrolets, have been made with non-adjustable rocker arms. The Crane Catalog shows you several ways of converting your engine to an adjustable rocker arm system. The following sections will describe how to set the preload with adjustable rocker arms.
Hydraulic Lifters Can Be Adjusted at Any Engine Temperature
Since hydraulic lifters can compensate for thermal expansion of the engine, the adjusting can be done with the engine cold; hot adjustment is not necessary.
I'm going to have to do it in 2 posts I guess.....
</TD></TR></TBODY></TABLE>
</TD></TR><TR><TD colSpan=2><HR></TD></TR><TR><TD colSpan=2>http://www.cranecams.com/?show=faq&id=3 Lifters (Hydraulic)
Hydraulic lifters have been the choice of the automotive industry for many years for several good reasons. when compared to a mechanical lifter, the hydraulics are:
1. Quieter.
2. Low maintenance.
3. An ability to adjust for thermal expansion of the engine.
4. Built in shock absorber, eases stress on valve train.
5. “Bleed Rate” can be designed to accommodate different engine RPM ranges.
Today’s modern engines all use either the standard design hydraulic lifter or the new low friction, high performance hydraulic roller design. Hydraulic lifters are the best for street applications, high performance, and mild racing applications where low maintenance is a primary concern.
What is the difference in the design of a Hydraulic and Mechanical Lifter?
Basically, the hydraulic lifter pushrod seat is moveable, the mechanical lifter seat is not. Both lifter types look the same from the outside, with both having pushrod seats held in by a retaining lock. The pushrod seat in a mechanical lifter usually registers upon an internal step inside the lifter body preventing it from moving (thus it gets the nickname “Solid Lifter”). What’s below the pushrod seat in the hydraulic lifter is a different story. Its pushrod seat is not restricted by a step, but instead sits on top of a moveable hydraulic mechanism which acts like a tiny hydraulic pump. Below this mechanism is valving and a spring to produce an upward force, moving the pushrod seat upward against the retaining lock.
What is Hydraulic Lifter Preload?
Mechanical cam designs require a running clearance or valve lash; hydraulic lifters are just the opposite. When the rocker arm assembly is properly torqued down into position, the pushrod must take up all the clearance and descend into the hydraulic lifter, causing the pushrod seat to move down by .020” to .060”. The distance that the pushrod seat moves down away from the retaining lock is the “Lifter Preload”. The hydraulic mechanism requires this precise amount of “preload” for it to do its job properly.
What happens if the amount of Hydraulic Lifter Preload is wrong?
If clearance exists between the pushrod and the seat in the hydraulic lifter, after the rocker arm assembly has been torqued down, you will have no lifter preload. In this case the valve train will be noisy when the engine is running. All of the hydraulic force produced by the lifter will be exerted against the lifter’s retaining lock, and this could cause the lock to fail.
If the opposite occurs and the pushrod descends too far (more than .060”), then you have excessive lifter preload. In theory, a hydraulic lifter can pump up whatever preload you put into it, therefore with excessive preload, as the engine RPM and oil pressure increases, the hydraulic mechanism will pump-up the pushrod seat. This will cause the valve to be open longer and lift higher. This will decrease the cylinder pressure, lowering the performance of the engine. If the preload is excessive it may cause “backfiring” from the engine. How to correct this situation will be explained in the next sections.
When rebuilding an engine, what can cause Lifter Preload to change?
Almost anything can affect lifter preload. If you do a valve job, surface the block or heads, change the head gasket thickness, or buy a new camshaft, the amount of preload can be affected. Sometimes these changes cancel one another out and your preload stays the same; this is more by luck than design. This is why you must always inspect the amount of preload the lifter has when reassembling the engine and be sure it is correct.
Fast and Easy Way to Check Hydraulic Lifter Preload when using Non-Adjustable Rocker Arms
With the cam, hydraulic lifters and pushrods in place, install your rocker arm assembly. Use the prescribed method in your repair manual and torque down all the valve train bolts in the proper sequence. Pick a cylinder that you are going to check. Hand rotate the engine in its normal direction of rotation until both valves are closed. You are on the compression cycle for that cylinder. (At this position the valve springs are at their least amount of tension making the job a little easier to do.)
Wait a few minutes, allowing the lifters to bleed down. Now, lay a rigid straightedge across the cylinder head, supporting it on the surface of the head where the valve cover gasket would go. Using a metal scribe and the straightedge, carefully scribe a line on both pushrods. Now carefully remove the torque from all valve train bolts, removing any pressure from the pushrods. Wait a few minutes for the pushrod seat in the hydraulic lifter to move back to the neutral position. Carefully scribe a new line on both pushrods.
Measure the distance between the two scribe marks, it represents the amount of lifter preload. If the lines are .020” to .060” apart you have proper lifter preload. If the lines are the same or less than .020” apart you have no or insufficient preload. If the lines are further apart than 060” you have excessive lifter preload. To bring your preload into tolerance, use one of the methods described in the next section if necessary, or call the Crane Tech Line for assistance (386/258-6174).
Methods to Adjust for Proper Hydraulic Lifter Preload
There are several different methods for increasing or decreasing the amount of lifter preload, depending on valve train design and how the rocker arm is held onto the cylinder head. Keep in mind that the automotive manufacturers have made changes to the valve train over the years. What may work on one year’s engine may not work for another, even though they are basically the same engine. There is one method that universally works on all these engines, change the pushrod length! Use a longer pushrod to increase preload, a shorter to reduce preload. Crane offers various length pushrods and offers custom length pushrods also.
Using Adjustable Rocker Arms to set Hydraulic Lifter Preload
The easiest method to arrive at proper lifter preload is when you have an engine with “Adjustable Valve Train”. Unfortunately, since 1967 most domestic engines, with the exception of small and big block Chevrolets, have been made with non-adjustable rocker arms. The Crane Catalog shows you several ways of converting your engine to an adjustable rocker arm system. The following sections will describe how to set the preload with adjustable rocker arms.
Hydraulic Lifters Can Be Adjusted at Any Engine Temperature
Since hydraulic lifters can compensate for thermal expansion of the engine, the adjusting can be done with the engine cold; hot adjustment is not necessary.
I'm going to have to do it in 2 posts I guess.....
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From: Erie PA
Adjusting Hydraulic Lifters for Proper Preload
In order to adjust the preload the lifter must be properly located on the base circle or “Heel” of the lobe. At this position the valve is closed and there is no lift taking place. You will need to watch the movement of the valves to determine which lifter is properly positioned for adjusting.
1. Remove the valve covers, and pick a cylinder you are going to set the preload on.
2. Hand rotate the engine in its normal direction of rotation and watch the exhaust valve on that particular cylinder. When the exhaust valve begins to open, stop and adjust that cylinder’s intake rocker arm. (Why? Because when the exhaust valve is just beginning to open, the intake lifter will be on the base circle of the lobe, the correct position for adjusting the intake.)
3. Back off the intake rocker arm adjuster and remove any tension from the pushrod. Wait a minute or two for that hydraulic lifter to return to a neutral position. The spring inside the lifter will move the pushrod seat up against the retaining lock if you give it time to do so. (If you are installing brand new lifters they will be in the neutral position when they come in the box.)
4. Now spin the intake pushrod with your fingers while tightening down the rocker arm. When you feel a slight resistance to the turning of the pushrod, you are at “Zero Lash”. Turn the adjusting nut down one quarter to one half turn from that point. Lock the adjuster into position. The intake is now adjusted properly.
5. Continue to hand turn the engine, watching that same intake. It will go to full open and then begin to close. When it is almost closed, stop and adjust the exhaust rocker arm on that particular cylinder. (Again, when we see the intake almost closed, we are sure that exhaust lifter is on the base circle of the lobe.) Loosen the exhaust rocker arm and follow the same procedure described before in steps 3 and 4 to adjust this rocker arm.
6. Both valves on this cylinder are now adjusted, and you can move on to your next cylinder and follow the same procedure again.
Do Hydraulic Lifters Need to be Primed with Oil?
Many people mistakenly believe that hydraulic lifters must be soaked in oil overnight and be hand pumped up with a pushrod before installing into a new engine, however this is not necessary. In fact, this could cause the lifter to act as a “solid” and prevent obtaining proper preload. What is very necessary is the priming of the entire engine’s oil system before starting up a new engine for the first time. This is done by turning the oil pump with a drill motor to force oil throughout the entire engine. Crane Cams offers oil pump primers for Chevrolet and Ford engines.
What is a “Fast Bleed” Hydraulic Lifter?
Part of engineering a hydraulic lifter is to determine what its “Bleed Rate” will be. The “Bleed Rate” is a scientific method of determining the time it takes the hydraulic lifter to lose its pressure once it is fully pumped up solid with oil. By changing this rate, the lifter can give different performance factors to the engine. One such design is the Crane Cams Fast Bleed Lifter. Its increased bleed rate enables it to provide improved vacuum, increased cylinder pressure and performance in the lower RPM ranges. It is best suited for those engines that are using a big camshaft profile that requires more compression ratio than the engine actually has. This situation would normally cause a loss of “bottom end” performance, but with the Crane Cams Fast Bleed Lifter the bottom end torque is restored.
NOTE: Fast Bleed Lifters are only for use if the compression ratio is below the recommended minimum shown on the application page for the particular camshaft you have selected.
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In order to adjust the preload the lifter must be properly located on the base circle or “Heel” of the lobe. At this position the valve is closed and there is no lift taking place. You will need to watch the movement of the valves to determine which lifter is properly positioned for adjusting.
1. Remove the valve covers, and pick a cylinder you are going to set the preload on.
2. Hand rotate the engine in its normal direction of rotation and watch the exhaust valve on that particular cylinder. When the exhaust valve begins to open, stop and adjust that cylinder’s intake rocker arm. (Why? Because when the exhaust valve is just beginning to open, the intake lifter will be on the base circle of the lobe, the correct position for adjusting the intake.)
3. Back off the intake rocker arm adjuster and remove any tension from the pushrod. Wait a minute or two for that hydraulic lifter to return to a neutral position. The spring inside the lifter will move the pushrod seat up against the retaining lock if you give it time to do so. (If you are installing brand new lifters they will be in the neutral position when they come in the box.)
4. Now spin the intake pushrod with your fingers while tightening down the rocker arm. When you feel a slight resistance to the turning of the pushrod, you are at “Zero Lash”. Turn the adjusting nut down one quarter to one half turn from that point. Lock the adjuster into position. The intake is now adjusted properly.
5. Continue to hand turn the engine, watching that same intake. It will go to full open and then begin to close. When it is almost closed, stop and adjust the exhaust rocker arm on that particular cylinder. (Again, when we see the intake almost closed, we are sure that exhaust lifter is on the base circle of the lobe.) Loosen the exhaust rocker arm and follow the same procedure described before in steps 3 and 4 to adjust this rocker arm.
6. Both valves on this cylinder are now adjusted, and you can move on to your next cylinder and follow the same procedure again.
Do Hydraulic Lifters Need to be Primed with Oil?
Many people mistakenly believe that hydraulic lifters must be soaked in oil overnight and be hand pumped up with a pushrod before installing into a new engine, however this is not necessary. In fact, this could cause the lifter to act as a “solid” and prevent obtaining proper preload. What is very necessary is the priming of the entire engine’s oil system before starting up a new engine for the first time. This is done by turning the oil pump with a drill motor to force oil throughout the entire engine. Crane Cams offers oil pump primers for Chevrolet and Ford engines.
What is a “Fast Bleed” Hydraulic Lifter?
Part of engineering a hydraulic lifter is to determine what its “Bleed Rate” will be. The “Bleed Rate” is a scientific method of determining the time it takes the hydraulic lifter to lose its pressure once it is fully pumped up solid with oil. By changing this rate, the lifter can give different performance factors to the engine. One such design is the Crane Cams Fast Bleed Lifter. Its increased bleed rate enables it to provide improved vacuum, increased cylinder pressure and performance in the lower RPM ranges. It is best suited for those engines that are using a big camshaft profile that requires more compression ratio than the engine actually has. This situation would normally cause a loss of “bottom end” performance, but with the Crane Cams Fast Bleed Lifter the bottom end torque is restored.
NOTE: Fast Bleed Lifters are only for use if the compression ratio is below the recommended minimum shown on the application page for the particular camshaft you have selected.
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