<VV> now lifter oil loss
jld at wk.net
Fri Dec 21 13:10:37 EST 2007
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.
At 10:19 AM 12/21/2007, BBRT wrote:
>Question. In a racing Corvair engine , running stock pump, remote
>cooler, 10 psi per thousand rpm ~ 70 psi or so, hydraulic lifters,
>turning up to 7500 rpm, why do lifters lose their adjustment,
>meaning clacking like the oil within the lifter is low, after a half
>hour on track? Are they improperly adjusted (nominal 5/8 turn)? Do
>the valves float causing the lifter not to continue to " pump up"?
>What is happening?
>From: "John Kepler" <jekepler at amplex.net>
>>FWIW, "stock" oil pumps move MUCH more oil than an engine can reasonably
>>handle, that's why there's a by-pass valve in the pump. Just because a
>>little is good, a lot isn't necessarily better!
More information about the VirtualVairs