Too little preload?
TT_Vert, Check your indicator mouting mechanism, it sounds like it is moving on you. What you are descibing is not possible, unless you were already past zero lash when you started measuring.
i checked it twice. The mount is not moving any. Its physically bolted to a rocker stud. The way the dial creeped up it was obvious the plunger was being depressed. The plunger on the dial indicator would move much sooner then the rigid mount I made would> I checked this 6 times and every time the needle would slowly creep from .020" all the way to .080"
Dave
Dave
How much is power effected by too little though? There seems to be many ways to check it and most of them are correct, but what are the effects of too much/too little? Thanks guys.
John
John
Heh...2 pages of talking about how to adjust and measure preload and the original topic starter never got his question answered. Good question John, I want to know too. What is the real reason we are all pulling our hair out for?
Here's some good info from Crane's website John. The measurements are for their lifters but the affects are probably the same for any hydraulic lifter.
What happens if the amount of Hydraulic Lifter Preload is wrong?
If clearance exists between the pushrod and the seat in the hydraulic lifter, after the rocker arm assembly has been torqued down, you will have no lifter preload. In this case the valve train will be noisy when the engine is running. All of the hydraulic force produced by the lifter will be exerted against the lifter’s retaining lock, and this could cause the lock to fail.
If the opposite occurs and the pushrod descends too far (more than .060”), then you have excessive lifter preload. In theory, a hydraulic lifter can pump up whatever preload you put into it, therefore with excessive preload, as the engine RPM and oil pressure increases, the hydraulic mechanism will pump-up the pushrod seat. This will cause the valve to be open longer and lift higher. This will decrease the cylinder pressure, lowering the performance of the engine. If the preload is excessive it may cause “backfiring” from the engine.
If clearance exists between the pushrod and the seat in the hydraulic lifter, after the rocker arm assembly has been torqued down, you will have no lifter preload. In this case the valve train will be noisy when the engine is running. All of the hydraulic force produced by the lifter will be exerted against the lifter’s retaining lock, and this could cause the lock to fail.
If the opposite occurs and the pushrod descends too far (more than .060”), then you have excessive lifter preload. In theory, a hydraulic lifter can pump up whatever preload you put into it, therefore with excessive preload, as the engine RPM and oil pressure increases, the hydraulic mechanism will pump-up the pushrod seat. This will cause the valve to be open longer and lift higher. This will decrease the cylinder pressure, lowering the performance of the engine. If the preload is excessive it may cause “backfiring” from the engine.
