Question on duration measurement

B

bubba_pa

New member
Joined
Oct 30, 2007
Messages
222
I've seen from other posts that your 181/210 is measured at 0.05" of lift. My question is this - is the measure direct from the cam (with a dial indicator tip) or do you take that measurement off of the lifter, rocker, or valve movement? My instincts tell me the lifter/rocker but I'm not sure. Seems that there are several ways of measuring duration and it's hard to compare apples to apples. Just trying to figure things out. If word-of-mouth means anything (and it usually does) - seems you have some great cams. Thanks for any help.

Paul
 
It was measured at the cam. With the low rocker ratios on these 24valves there is not much variation between cam and valve duration numbers. The larger the rocker ratio the more variation. The crazy thing is that after lash and rocker ratio is factored in it is almost the same at the cam and at the valve. With varrying ramp rates lash can have a major affect in the reading. With .020 lash on the exhaust and slower ramp rates, there will be quite a reduction in duration reading at the valve.


Zach
 
You must log in or register to reply here.
Back
Top