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All hydraulic work by the same principle.The annular groove on the outside of the lifter shell is what supplies oil preasure to the lifter so it can do it's job of maintaining "Zero Lash"(clearance) between the camshaft and the valve stem-and therfore no noise in the valve train.The oil preasure is what supplies the lifter the ablity to be "pumped up" to maintain "Zero Lash" when the lifter is under no load from the cam(call the base circle period of the cam).The oil preasure spreads open(apart) the lifter shell and the internal plunger.The lifter has the outer shell that the cam presses on,and it's internal parts are a plunger(that sits on the valve stem)with a internal spring loaded ball check valve.The check valve is what closes when load to the lifter,so blocks the oil passage,and locks the lifter in it's "Zero Lash" position.This must happen quickly or the lifter colaspes and makes noise because clearance is now introduced between the cam and the valve stem.
A lifter is made to close internal clearances,so the plunger can move in the lifter shell bore,yet not so close that it will become stuck in the bore.It must be close so it won't allow oil to leak past it's clearance.If the plunger becomes stuck in the liffter shell bore so it can't move,you have a stuck or stickey lifter.If the ball check valve assembly won't seal fast enough ,it allows the lifter to leaks down and is colasped under the load the cam applies.Both conditions allow valve train noise.
When i assemble a motor,i place the lifters upside down in oil so i can pump the lifters up(vents the air out of the lifters)and make sure the lifter lock up and don't colaspe.That's the way i check lifters and it allows a quite motor on first start up. A good lifter too me is one the i can pump the air out of and locks up and won't colaspe under the load i develop when i press on it
There is a machine that you place a pumped up lifter on under a certain load and you measure the time it takes a lifter to colaspe to check a lifter to see if it meets it specs for operation.Hope this helps you out.Most lifters can be disassembled and cleaned.I have done it to american and Saab lifters.
posted by 4.156.10...
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