Lifters
From Crankshaft Coalition Wiki
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| − | [[File:Hydraulic Lifter.jpg|thumb|200px|left|Generic hydraulic lifter]][[File:Schubeck hydraulic lifter made for zero lashing.jpg|thumb|150px|right|[http://www.schubeckracing.com/flathydraulic.html '''Schubeck hydraulic lifter'''] made to be zero-lashed]] <br><br> | + | [[File:Hydraulic Lifter.jpg|thumb|200px|left|Generic hydraulic lifter (c) 2007 ratwell.com]][[File:Schubeck hydraulic lifter made for zero lashing.jpg|thumb|150px|right|[http://www.schubeckracing.com/flathydraulic.html '''Schubeck hydraulic lifter'''] made to be zero-lashed]] <br><br> |
==Overview== | ==Overview== | ||
| − | The lifter of an overhead valve engine rides on the cam lobe, actuating the push rod that directs the movement to the valve stem. It is an essential part of the valve train and the importance of a proper break in between the lifter foot of a flat tappet and the cam cannot be overstated. | + | The lifter (or "tappet") of an overhead valve engine rides on the cam lobe, actuating the push rod that directs the movement to the valve stem. It is an essential part of the valve train and the importance of a proper break in between the lifter foot of a flat tappet and the cam cannot be overstated. |
==Types of lifters== | ==Types of lifters== | ||
| − | Lifters are either hydraulic or solid. They can be either a "flat tappet" type, or a roller type. These two types can be either hydraulic or solid (also called "mechanical") | + | Lifters are either hydraulic or solid. They can be either a "flat tappet" type, or a roller type. These two types can be either hydraulic or solid (also called "mechanical"). |
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===Flat tappet=== | ===Flat tappet=== | ||
| − | Flat tappet lifters are | + | Flat tappet type lifters are actually not perfectly flat, they have a very gradual radius ground onto them to help the lifter to rotate (along with the angle of the cam lobe). Most flat tappet lifters resemble a cylinder of steel with an internal snap ring on one end holding in a pushrod cup. |
Flat tappet cam/lifter valve trains were the primary form of valve actuation for domestic engines from the early '50s until about the mid-'80s. They were reasonable durable and reasonably reliable, although there were better designs. Not until the EPA mandated a change in the motor oil formulations did they fall out of favor. | Flat tappet cam/lifter valve trains were the primary form of valve actuation for domestic engines from the early '50s until about the mid-'80s. They were reasonable durable and reasonably reliable, although there were better designs. Not until the EPA mandated a change in the motor oil formulations did they fall out of favor. | ||
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| + | ====Flat tappet lifter foot==== | ||
| + | The lifter foot of a flat tappet lifter is not perfectly flat, instead it is slightly convex. This is done to allow the lifter to rotate, and the shape of the lifter combined with the shape of the cam lobe is what causes this rotation. The rotation of the lifter keeps the highly loaded interface between the lifter and cam lubricated and cooled so as to not cause excessive wear during operation. | ||
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| + | [[File:Cam lobe angle.jpg|thumb|left|300px|Exaggerated view of flat tappet lifter crown and cam lobe]]<br style="clear:both"/> | ||
====Mushroom flat tappet lifter==== | ====Mushroom flat tappet lifter==== | ||
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===Hydraulic lifter=== | ===Hydraulic lifter=== | ||
| − | The hydraulic lifter | + | The hydraulic lifter has been a mainstay for over 40 years in domestic automobile engines. Its design allowed a basically maintenance free valve train. They are usually quiet and reliable. |
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| + | The hydraulic lifter was invented as a means of reducing maintenance and quieting the valve train. Generally the pressure from the engines oil pump would provide the "self adjusting" hydraulic action and keep the lifter tight to the camshaft and push-rod. This action was well controlled by design within the normal operating ranges of most passenger vehicles although over-extension, known as lifter "pump up" of the lifter can occur at elevated RPM, allowing the valves to be held off the seat causing a loss of power. This means mechanical lifters are the preferred type of lifter for high RPM applications. Later versions of performance hydraulic lifters included anti-pump up-types and roller lifter types as well. | ||
| + | *[http://www.youtube.com/watch?v=lorANZ1Tptw '''Click here'''] for a video that shows an animation of a hydraulic lifter. | ||
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[[File:Lifter cutaway preload.jpg|border|400px|right]] | [[File:Lifter cutaway preload.jpg|border|400px|right]] | ||
[[File:Pontiac service manual lifter diagram.jpg]] | [[File:Pontiac service manual lifter diagram.jpg]] | ||
| − | ====Fast bleed down lifter==== | + | |
| + | ====Fast bleed down hydraulic lifter==== | ||
An example of a fast bleed down hydraulic lifter is the [http://www.rhoadslifters.com/ Rhodes] lifter. The Rhodes lifter accomplishes the fast bleed down by machining a precision groove on the plunger, possibly by using EDM (electron discharge machining) or laser. This groove allows the oil to bleed out of the lifter at a faster- yet controlled- rate. This allows the lifter to lower the lift and duration of the cam at lower RPM, typically from idle to ~3000 RPM or so, depending on the valve spring pressure and oil viscosity. At higher RPM, the lifter behaves as a normal lifter would. | An example of a fast bleed down hydraulic lifter is the [http://www.rhoadslifters.com/ Rhodes] lifter. The Rhodes lifter accomplishes the fast bleed down by machining a precision groove on the plunger, possibly by using EDM (electron discharge machining) or laser. This groove allows the oil to bleed out of the lifter at a faster- yet controlled- rate. This allows the lifter to lower the lift and duration of the cam at lower RPM, typically from idle to ~3000 RPM or so, depending on the valve spring pressure and oil viscosity. At higher RPM, the lifter behaves as a normal lifter would. | ||
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===Solid lifter=== | ===Solid lifter=== | ||
| − | + | Originally, virtually all lifters were a solid or "mechanical" lifter design that required regular maintenance to check and set clearance in the valve train to account for wear during normal engine operation. This insured that the valve would fully seat against the valve seat, which is important not only for good engine performance but for the valve (especially the exhaust valve) to transfer heat from the valve into the seat then on to the cooling system to prevent the valve from rapidly eroding (aka a "burned valve"). | |
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| + | With a solid lifter valve train, a predetermined amount of play is introduced between the tip of the closed valve and the rocker arm. This clearance is sufficient to allow for heat expansion of the components during operation. | ||
The solid lifter valve train requires periodic maintenance to account for wear, else the valve could eventually be damaged by insufficient clearance. That causes the exhaust valve to overheat and/or burn and a loss of performance can result from the intake not seating and sealing as it should. Excessive clearance can cause valve train damage and reduced performance and mileage. | The solid lifter valve train requires periodic maintenance to account for wear, else the valve could eventually be damaged by insufficient clearance. That causes the exhaust valve to overheat and/or burn and a loss of performance can result from the intake not seating and sealing as it should. Excessive clearance can cause valve train damage and reduced performance and mileage. | ||
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Solid flat tappet lifters are still used in some high performance engines, solid roller valve trains are the choice for racing when allowed and street/strip engines used at high RPM. They are as durable as a hydraulic lifter in flat tappet form, but suffer the same wear problems due to the decrease of wear additives that have been removed from current motor oil. | Solid flat tappet lifters are still used in some high performance engines, solid roller valve trains are the choice for racing when allowed and street/strip engines used at high RPM. They are as durable as a hydraulic lifter in flat tappet form, but suffer the same wear problems due to the decrease of wear additives that have been removed from current motor oil. | ||
| − | Solid lifters are not used in modern engines because they make enough noise that they could confuse knock sensors. | + | Solid lifters are not used in modern engines because they make enough noise that they could confuse knock sensors, and the need for periodical maintenance is seen as too costly for the manufacturers to do under warranty. |
===Roller lifter=== | ===Roller lifter=== | ||
| + | ====GM hydraulic roller lifter==== | ||
Shown below is a GM hydraulic roller lifter. The arrow shows the location of the cup, spring and check ball assembly mentioned [[Lifters#Disassembling a hydraulic lifter|'''below''']]. | Shown below is a GM hydraulic roller lifter. The arrow shows the location of the cup, spring and check ball assembly mentioned [[Lifters#Disassembling a hydraulic lifter|'''below''']]. | ||
[[File:Oem hyd roller lifter expolded view.jpg|left|frame|OEM GM hydraulic roller lifter]] | [[File:Oem hyd roller lifter expolded view.jpg|left|frame|OEM GM hydraulic roller lifter]] | ||
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| + | The Cadillac CTS-V lifters, GM-88958689 (a set of 16 are ~ $300.00 as of mid-2013) will not withstand excessive valve spring pressure. The Cadillac CTS-V lifters are lighter but are not able to handle high spring pressure any better than standard Chevrolet LS-7 lifters (GM-12499225, set of 16 go for ~ $140.00 as of mid-2013). Either of these lifters are designed to be used with </= 100 lb. seat pressure and </= 300 lb. open pressure. If using more pressure with standard weight valve train components (no titanium, etc.), you should consider using an aftermarket hydraulic roller lifter like Comp Cams 'Reduced Travel' p/n 875 or Comp Cams p/n 15850 'Short Travel' hydraulic roller lifters (use with OEM dog bone retainers), made for OEM hydraulic roller blocks. These lifters use a very small preload (0.000 to 0.005") and the total travel is just 0.050". | ||
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| + | GM uses the p/n 12499225 (AC Delco p/n HL-124) roller lifters as service replacements in all Chevrolet 1991 to 2013 (and likely beyond) engines. Don't use lifters designed for use in net lash valve trains (example is AC Delco p/n HL-105, GM p/n 5234670); severe engine damage can occur due to lifter loft/pump up. | ||
==How to tell a hydraulic lifter from a solid lifter== | ==How to tell a hydraulic lifter from a solid lifter== | ||
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{{Note1}}If trying to repair a bad lifter and the lifter's inner bore is OK but the plunger is found to be unrepairable, replace the plunger assembly from another identical lifter and reuse the lifter body, then replace the lifter back on the same lobe it came from. | {{Note1}}If trying to repair a bad lifter and the lifter's inner bore is OK but the plunger is found to be unrepairable, replace the plunger assembly from another identical lifter and reuse the lifter body, then replace the lifter back on the same lobe it came from. | ||
| − | The lifter is the most precisely machined part in the engine. The plunger OD is matched to the lifter body ID | + | The lifter is the most precisely machined part in the engine. The plunger OD is matched to the lifter body ID; the close tolerances are required to give the correct amount of bleed down. For that reason, there is a chance you might need to go through more than one lifter to find a good match to the old plunger OD. The MAIN thing is that the plunger not be too tight. Slightly loose will still perform OK, although there's a chance there could be some slight tapping at idle. But if the lifter and cam cannot for whatever reason be replaced as a set, this is STILL preferable to putting a new lifter on a used cam. |
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[[Category:Engine]] | [[Category:Engine]] | ||
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[[Category:Camshaft]] | [[Category:Camshaft]] | ||
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