<VV> Clattering Lifters

[JVHRoberts at aol.com]

The one other cause of noisy lifters I've discovered is excessively aerated  
oil. The clue was, the more full the crankcase, the quieter they were. My 
theory  is, the more oil, the more time it has to let the air float out. I also 
had one  engine with a loose oil pickup that clattered to beat the band! When I 
had the  pan off to fix a pan leak, I pulled the pickup, put a thin layer of 
sealant on  it, and VOILA! Lifters were quiet afterwards. 
 
Given that higher mileage Corvair engines tend to be leakers/oil burners,  
low oil level can also do it. I've had troubles with anything less than up to  
the full line, and have sometimes gone over that. 
 
In a message dated 12/21/2007 1:41:30 P.M. Eastern Standard Time,  
vairologist at verizon.net writes:

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.
---------------------------------------------
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.


 



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