Lifters
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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> | |
| + | ==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 its importance cannot be overstated. | ||
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| − | Lifters are either hydraulic or solid. They can be flat | + | ==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"). | ||
| + | ===Flat tappet=== | ||
| + | Flat tappet lifters are flat on the bottom. Actually they're 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), and resemble a cylinder of steel with a 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. | |
| − | ==Roller== | + | ====Mushroom flat tappet lifter==== |
| − | Shown below is a GM hydraulic | + | Mushroom lifters were used in high performance flat tappet applications. The larger diameter of the mushroom lifter's foot allowed it to handle more aggressive cam lobe profiles. They weren't used on production engines much at all, the assembly process when using them is labor intensive- something the OEM always tries to avoid. |
| − | [[File:Oem hyd roller lifter expolded view.jpg|left|frame|OEM GM hydraulic roller]] | + | |
| + | ===Break in of flat tappets=== | ||
| + | The motor oil formulation has been changed due to concerns for the environment. These changes involved, in part, a reduction of the wear additive essential for a flat tappet cam to survive the harsh conditions they operate under. Because of this, special steps must be taken at break in and at oil changes to prevent premature wear or failure of the flat tappet cam and lifters. | ||
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| + | For more on the steps that need to be taken to avoid a cam and lifter failure, see [http://www.crankshaftcoalition.com/wiki/Camshaft_install_tips_and_tricks Camshaft install tips and tricks]. | ||
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| + | ===Roller=== | ||
| + | Shown below is a GM hydraulic roller lifter. The arrow shows the location of the cup, spring and check ball assembly mentioned [[Lifters#Replacing lifters|'''below''']]. | ||
| + | [[File:Oem hyd roller lifter expolded view.jpg|left|frame|OEM GM hydraulic roller lifter]] | ||
<br style="clear:both"/> | <br style="clear:both"/> | ||
| − | == | + | ==Hydraulic lifter== |
| + | The hydraulic lifter was a mainstay for over 40 years in domestic automobile engines. Its design allowed a basically maintenance free valve train. They were quiet and reliable. | ||
| + | [[File:Lifter cutaway preload.jpg|border|400px|right]] | ||
| − | === | + | ===Fast bleed down=== |
| + | 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 putting a groove on the plunger by EDM (electron discharge machining) or laser. This groove allows the oil to bleed out of the chamber at a faster, yet controlled rate. This allows the lifter to vary 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. | ||
| + | <br style="clear:both"/> | ||
| + | Below, the groove on the plunger can be seen at the arrows. The plunger is partially removed from the lifter body; the retainer clip and pushrod cup were previously removed. | ||
| − | + | [[File:Rhodes lifter groove.jpg]] | |
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| − | + | ===Anti pump up=== | |
| − | + | ==Solid lifter== | |
| + | Before the hydraulic lifter, the solid or "mechanical" lifter was used exclusively. 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. | |
| − | =Replacing lifters= | + | 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. |
| − | Before replacing a stuck or noisy lifter (which should only be done as a LAST resort), disassemble the lifter that is in question. You will see a cup, spring and check ball | + | |
| + | Solid lifters are not used in modern engines because they make enough noise that they could confuse knock sensors. | ||
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| + | ==Replacing lifters== | ||
| + | [[File:Lifter expolded view.jpg|thumb|200px|left|Arrow points to check ball retainer]] | ||
| + | [[File:Lifter clips 002.jpg|thumb|350px|Three styles of lifter cup retainers. The [http://www.truarc.com/pdfs/Truarc%20Catalog.pdf internal C-clip type] is stronger and should be used especially with solid lifters or when "zero lashing" lifters.]] | ||
| + | Before replacing a stuck or noisy lifter (which should only be done as a LAST resort), disassemble the lifter that is in question. You will see a cup, spring and check ball retainer (left) snapped onto the bottom center of the "piston" of the lifter. Often all that has happened is the cup assembly isn't fully seated into the recess on the bottom of the piston, or a speck of dirt has lodged between the check ball and seat. <br style="clear:both"/> | ||
Remove the cup using a pick and see that the tiny spring and check ball are there and that the ball isn't scored and that the seat on the piston that the ball seals, doesn't have any ridge or imperfections that would prevent the ball from seating properly. | Remove the cup using a pick and see that the tiny spring and check ball are there and that the ball isn't scored and that the seat on the piston that the ball seals, doesn't have any ridge or imperfections that would prevent the ball from seating properly. | ||
| − | A better choice if the lifter's piston is found to be unrepairable, would be to replace the piston (from another lifter) and reuse the lifter body that has broken in to the lobe that it started life running on. The lifter foot and the cam lobe quickly wear in together to become a unit- using a new lifter risks wiping out the cam lobe. | + | A better choice if the lifter's bore is OK but the piston is found to be unrepairable, would be to replace the piston (from another lifter) and reuse the lifter body that has broken in to the lobe that it started life running on. The lifter foot and the cam lobe quickly wear in together to become a unit- using a new lifter risks wiping out the cam lobe. |
[[Lifters#Types of lifters|'''Return to top''']]. | [[Lifters#Types of lifters|'''Return to top''']]. | ||
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| + | ==Resources== | ||
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[[Category:Engine]] | [[Category:Engine]] | ||
| − | [[Category: | + | [[Category:Adjust valves]] |
| + | {{youcanedit}} | ||
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