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Old 03-07-2005, 06:28 PM
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hydraulic cams/lifters

Could someone give me a good link or detailed explanation of how hydraulic cam and lifters work compared to solid cams and lifters and advantages and disadvantages? thanks bf

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Old 03-07-2005, 06:49 PM
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basically the only difference is in the lifters.. hydraulic lifters have a small piston inside.. and use the oil as a kind of hydraulic coushin... solid are just solid pieces of metal... no coushin.. i would suppose the solid would be a little harder on the valvetrain...also i think solid camshafts are harder metal.. due to no give in the lifters... hydraulic can be a little softer because the lifters have a coushin
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Old 03-07-2005, 07:29 PM
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The diffrences in Hyd. and solid lifters is the hyd. lifters are more suited for the street. Now a solid lift cam will make more power but you have to pull the valve covers about every week to adjust the valve lash. Not cool. thats why solid lifters are better suited for the track where you have to test and tune on a motor all week before you take it to the track and hyd. lifters are the best choice for the street cause of the low mantnance.

Hope some of this helps.

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Old 03-07-2005, 08:23 PM
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Thats not nessecarily true about having to adjust the lifters all the time. I know several people who have solid cams and they are reletivily trouble free.
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Old 03-07-2005, 08:46 PM
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solid vs hydraulic

Solid lifters have been around since the inception of the cam operated valve in a 4 cycle engine.
Solid lifters require a clearance set in the valvetrain to compensate for expansion of the metals. Hense with solid lifters, you will get a lash setting on your cam card, usually reading somewhere between .018- .022", and this is set with a feeler gauge between the nose of the rocker arm and the tip of the valve.
Hydraulic lifters use oil to set this lash so setting lash on a hydraulic cam is far less critical. The way a hydraulic lifter works is that there is a port in the side of the lifter that allows pressurized oil to enter it from the lifter gallery. Being that the lifter is hollow and there is a port in the spring loaded disc in the top of the lifter, access oil is bled off through this port and travels on up through the hollow pushrod and shoots oil all over the rocker arm.
When the lifter on a Solid lifter cam starts up the ramp, what slack there is in the valve train, due to the lash setting is taken up til everything is metal to metal and the pushrod starts lifting the heel of the rocker arm, which in turn depresses the valve, opening it.
IN a hydraulic lifter, when that disc in the top closes the port in the side of the lifter, then the aforementioned slack is taken up and the same event occurs.
The advantage to hydraulic lifters are that they are quiet, in that you dont hear a constant ticking noise, as you will with solids, and as mentioned previously, you dont have to adjust hydraulic lifters as a general rule, as you do occasionally have to do with solids. Properly set solid lifters, should be good for approximately 30-40,000 miles, under normal driving conditions. Before the advent of hydraulic lifters, when vertually all vehicles ran solid lifters, valve adjustment every 30,000 miles or so was a common occurance.
Solid lifters are made from higher tensile strength iron than are hydraulic lifters, due to the pounding they take, as occured by the lash.
Advantages of solid lifters, due to lobe profile, you will get more lift with a solid lifter cam for a given duration than you will with a hydraulic, and since solid lifters generally open faster on the ramps than do a hydraulic, you also will have more open valve area under the lift curve as well, even with the same lift on both cams.
Disadvantages to a hydraulic lifter. as the lifter returns to the heal of the cam, the lifter may well be extended to its full length, allowing it to fill with oil, and in doing so at high RPM, wont allow the valve to return completely to its seat. This is referred to as pump up, sometimes erroniously called valve float, but the results of both can be the same, bent parts or lost power at least, til the engine drops back to the operational power band the valve train is designed for.
On the issue of valve float, a better term would be valve bounce, as what happens is that at some point you try to turn higher rpm than the springs want to work at. When this happens, the valves will come back down on the seat with more force than the valve spring can handle, allowing the valve to actually bounce on its seat.
This can happen with any kind of cam, regardless of its type.
This phonomenon can be caused by the spring not being able to keep the lifter on the face of the cam as it comes over the top, allowing the lifter to possibly come from contact with the lobe face, this usually being the cause of the afformentioned dancing valve, as the valve will suddenly drop into place, and the spring wont hold it there.
While solid lifters will put out nominally more power than will a hydraulic, the fact is that unless you are building an engine that is intended to operate in an RPM range over 7000 RPM, for the most part, going with a solid lifter cam and dealing with the extra maintainance is not worth the extra expense.
As a general rule, taking a hydraulic and a solid lifter cam of the same power band and other things being equal, there will be little noticeable difference in power outputs.
Rule of thumb, a solid lifter cam requires 10 degrees more of duration to operate in the same power curve as a hydraulic. From that point, a 220 degree hydraulic cam operates in the same rpm range as a 230 degree solid lifter unit.
If you are building a road burner and getting the total umpth in horsepower isnt a super criteria, you are about as well off to go with hydraulic cams anyway, and save a few bucks you can put elsewhere.
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