DONAIMIAN

iTrader: (18)

Whats the differnece and/or the relation betwene advritised duration, and duration @.050. Im more familiar with the .050 stuff, but why is that used more that the advritised duration <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" />

Old SStroker

Try this; page 8 from Comp Cams catalog:


http://www.compcams.com/catalog/008.html

DONAIMIAN

iTrader: (18)

Thanks. That helped me understand it a little better, but im still a little blurry on it. Anyone else

MyLS1Hauls

iTrader: (2)

There are basically two industry standards for rating duration on a cam. One indicates the amount of duration at .050" lift at the valve. This is the one you are used to hearing...as in the TR220...it has 220 deg. of duration at .050" valve lift. It also has 270* duration at .006" lift at the lifter. The valve is open for 270 degrees of crankshaft rotation with the lifter at or above .006" lift. This allows you to see more about the profile of the lobe. Take the off the shelf comp cams 216/220 cam. It has 269 degrees of advertised duration on the intake and 273 on the exhaust. Compare that to the thunders specs. You will see that the TR220 has less timing at the .006, but the same .050" as the exhaust valve on the off the shelf comp. I know this is wordy, but hopefully it helps lol. <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />

Brad

LS1derfull

Brad said most of what needs to be said on subject but i want to add that duration at .200" lift and lift at TDC are even sharper way of comparing what cam profile is packing. Jason at Thunder Racing stated that most important cam event is intake valve closing point and after playing the field with this i have to agree with him 100%. Cylinder filling ability at peak piston
speed and trapping as much cylinder pressure at low speeds is what sets winners from losers at cam, spec choices.

DONAIMIAN

iTrader: (18)

ok I totlay understand it now, Advritises it at the lifter and .050 is at the valve stem.
Thanks everyone <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />