<VV> Clattering Lifters

[Smitty Smith]

  From: James Davis 
Subject: Re: now lifter oil loss
Any time lifters "pump up" it is because of loft on the cam lobe nose 
. In other words the lifter is not following the cam lobe. Cure is 
heavier valve springs, different cam lobe profile, lighter valve 
train components, stiffer push rods, less rpm ;-). The usual 
culprit valve is operating the engine at a rpm that is at the valve 
spring resonance frequency or one of its harmonic 
frequencies. Lifter collapsing can be due to several problems: low 
oil pressure, oil contamination, lifter pump clearance, non circular 
base circle on the camshaft, high valve spring pressure; to name a 
few. .Usually lifters that work correctly when the oil temperature 
is cool and collapse when the engine oil is hot is due to the oil 
viscosity/valve spring pressure. In other words, the lifter pump 
relief valve cannot overcome the valve spring pressure plus valve 
train inertia pressures at high rpm.
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  Smitty Says:  Jim you mention contamination as one reason, and the most likely contamination is air being whipped into the oil by all the violence going on around the crankshaft.  You can hardly expect a lifter that counts on the non-compressability of oil to keep its zero lash adjustment, when the oil is 30% tiny air bubbles like a milk shake.