[Steve C.]

Keep in mind that many lobe profiles are much slower on the closing side. Relates to this, a hint from the designer of UltraDyne cams & Voodoo lobes........

"I do all my cam designs as unsymmetrical cam designs. Although I design my hydraulics just like I do my roller profiles, The information I will give applies just to my hydraulic flat profiles.
Using Harvey Crane's Hydraulic Intensity formula, ALL my .842" tappet designs have an Hydraulic Intensity of 53.88 degrees. This is the duration at .050" subtracted from the duration at .004", where the SAE has decided that hydraulic durations begin and end.
This Hydraulic Intensity of 53.88 is considered to be very aggressive, yet the cams do not have that 'sewing-machine' sound to them.
The opening side of the cam has a 45.26 degree equivalent Hydraulic Intensity, and the closing side is 62.50 degrees Hydraulic Intensity. The SEATING velocity of the valve is only 37% as fast as the OPENING velocity. This seating velocity is only slightly faster than GM uses on all their engines. At UltraDyne, I have had many hydraulic, as well as solids, go over 100,000 miles on the street. I keep the edge of the tappet about .018" away from the point of contact between the cam and tappet.
That 'sewing-machine' sound is caused by the valves hitting the valve seats too fast. The original High Energy cams, which I designed, produced that sound. I was shutting the valve at .0007"/*, only .0002"/* faster than GM. After hearing about the noise, a little thought made me realise the .0002"/* was only 40% faster than GM.
You do not have to shut the valve faster to keep the charge from getting out.
You have to design the cam so the charge, or inertia ram, is still filling the cylinder when you shut the valve.
Every cam I design, hydraulic, hydraulic roller, solid, solid roller, is designed using the same theory I have used for the past 29 years, and they all make excellent bottom-end torque for their duration."
UDHarold


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