They go all the way back to the earliest days of the internal combustion engine. The earliest engines did not have pushrods or rocker arms. Click Here to Read More Advertisement Valve lifters play a key role in the valvetrain of pushrod engines. It was a simple design but not the best configuration for breathing efficiency or horsepower. The overhead valve design added complexity to the valvetrain because it required the addition of pushrods and rocker arms.
The lifters also had to route oil up through the pushrods to lubricate the upper valvetrain components. However, most modern OHC engines do have some type of hydraulic valve lash adjusters. The basic function of a valve lifter is pretty simple. It sits on the camshaft and transfers the motions of the cam lobe up through the pushrods and rockers to open and close the valves. The size and shape of the cam lobe under the lifter multiplied by the ratio of the rocker arms determines valve lift and duration.
As such, the lifter just follows the motions of the cam. But it does play a role in valvetrain lash clearance and noise. It has a hard faced bottom that rides on the cam, and a cup on top that supports the lower end of the pushrod.
The lifter has an inlet hole in the side so pressurized oil can fill the lifter body, and an outlet hole in the center of the pushrod cup so oil can flow up through the pushrod to lubricate the upper valvetrain components. But actually on most applications the bottoms of the lifters are slightly convex. The center is about. Also, the lobes on flat tappet cams are not perfectly flat but have a slight taper.
In addition, the centerline of the lifters are offset slightly with respect to the cam lobes. This makes the lifters rotate as the cam turns, which helps to reduce friction and wear. Advertisement The area of contact between the lifters and cam lobes is the highest loaded surface inside an engine, with as much as , to , PSI at the point of contact depending on valve spring pressure!
Consequently, it is critical that both components have the correct geometry both convex and taper , that both surfaces have adequate hardness to resist premature wear and failure, and that the point of contact receives good lubrication with a motor oil that contains sufficient levels of high pressure anti-wear additive such as ZDDP. Lubrication has been a problem in recent years because the amount of ZDDP in motor oil has been significantly reduced to prolong the life of catalytic converters.
Reducing ZDDP to less than ppm has not created a problem for most late model engines because they have low friction roller lifters or overhead cam followers.
But in older engines with flat tappet cams, using a low ZDDP motor oil may not provide adequate wear protection for the cam and lifters — especially if stiffer valve springs are installed. Some suppliers offer lifters that have a small pinhole burned through the bottom center of the lifter body to direct oil right to the cam lobe.
Another supplier grinds several small flats only a few thousandths of an inch deep down the sides of their lifters so more oil can flow down onto the cam. A big improvement came about with the invention of roller lifters. By placing a small wheel on the bottom of the lifter, friction between the cam and lifter is greatly reduced.
Roller lifter also allow the use of more radical cam lobe profiles with faster opening and closing ramps that allow more total valve opening for a given lift and duration. Advertisement Mounting a wheel on the bottom of the lifter also changes the dynamics between the lifter and cam. This requires the addition of a linkage bar between adjacent lifters to keep them straight, or machining the lifter body and lifter bores with a flat to prevent them from twisting. One of the differences between a roller cam and a flat tappet cam is that the lobes on a roller cam are truly flat whereas those on a flat tappet cam have a slight taper.
If the wrong type of cam or lifters are used together flat tappet cam with roller lifters, or a roller cam with flat tappet lifters , the mismatch will cause bad things to quickly happen. Advertisement Something else that should never be done when rebuilding an engine is to install a new cam with used lifters. The cam and lifters develop a specific wear pattern to each other as they seat in.
If a high mileage cam is worn, or one or more lifters show concave wear on the bottom, the cam and lifters all need to be replaced. I don't want to start taking a new motor apart if it isn't necessary. Scott Sortor Via email. A missing plug on a brand-new-quality, GM-built engine is highly unlikely. I'm On traditional small- and big-block Chevys, the right-hand passenger-side lifters and valvetrain are fed oil from an annular groove located near the bottom of the distributor housing just above the driven gear that transfers oil from the main center oil passage in the block.
If the primer tool lacks a similar groove or if any existing groove doesn't properly align with the center main oil feed and right-hand lifter oil passage, the result is a massive internal oil leak and the right-side lifters and valvetrain won't pressurize.
Solid lifters must be adjusted periodically, at every 30, miles or so. If the lash or gap in the solid lifter adjustment is off, it can cause lifter and cam wear. Bent push rods will also alter the lash adjustment and must be replaced. Valve lifters are one of the first components to suffer wear when the oil pressure is consistently low. Low oil pressure can result from a number of factors, including excessive camshaft end play and worn cam bearings, worn oil pump gears, worn crankshaft journals and bearings and worn main and rod bearings.
Any small oil passage in the engine can restrict flow and cause low oil pressure. Low oil pressure shows up as a dash warning light or oil pressure gauge reading. Worn lifters, or excessively low oil pressure, will often produce a clacking or clicking sound, especially during engine warmup.
The sound originates from collapsed hydraulic lifters that are frozen, or from solid lifters that have worn excessively and changed lash tolerances. An engine miss usually accompanies a bad lifter, usually originating from the affected cylinder. Lifter tick can happen due to dirt in your engine oil, low engine oil levels, improper lifter spacing, or overall faulty lifters.
You can get rid of the lifter ticking sound by changing the engine oil, clean the lifter with oil additives, adjust the lifter spacing, and in rare cases replace the entire lifter.
Valve lifters are one of the first components to suffer wear when the oil pressure is consistently low. Any small oil passage in the engine can restrict flow and cause low oil pressure. Low oil pressure shows up as a dash warning light or oil pressure gauge reading. Usally mins will do it but most of the time I can get them to pump up in the first min by holding the throttle rpm.
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