Cams; Advertised duration vs. .050 duration
Racer
Joined: Apr 2007
Posts: 361
Likes: 0
From: Sacramento (Citrus Heights) California
Dwell over nose is an important consideration too, but only if you're going to be doing SERIOUS number crunching.
Tech Contributor
Joined: Aug 1999
Posts: 14,382
Likes: 6,401
From: At my Bar drinking and wrenching in Lafayette Colorado
There is no conversion or relation between the two. Ramp profiles and methods of determining "advertised" numbers make that impossible and irrelevant. Just use the .050 numbers - it's the only spec that means anything and that can be compared from one cam to another.
Thread Starter
Safety Car
Joined: Feb 2006
Posts: 4,855
Likes: 2
From: Columbia South Carolina
This is what I thought, I guess I was looking for confirmation. Trying to compare two cams from different manufacturers and two different sources, Jegs typically displays 'advertised duration' and Summit displays '.050 duration' I was over thinking the problem. Thanks for the help and advice
Le Mans Master
Joined: Apr 2007
Posts: 7,353
Likes: 72
From: Graceland in a Not Correctly Restored Stingray
In lieu of an official industry standard, 0.050" numbers give one a fairly straightforward indication, but not the full picture. So, IMHO it's more like an apples to pears comparison.
To get a better idea of a cam's profile, in addition to looking at 0.050" numbers it's a good idea to see what the 0.200" specs are. And, the advertised specs are still important, tho harder to quantify with there being no industry standard, since valve opening and closing events are specified at that point and the lash ramps can vary how the profile begins its approach to 0.050", also.
Of course, for those who want more detail you could check the specs of Cam Dr or Cam Pro Plus files on the cam(s) in question. Then there's Perf Trends' Cam Analyzer w/test stand setup if you reeealy want to see what you've got in your hands.
For most of us, the 0.050" numbers will suffice
To get a better idea of a cam's profile, in addition to looking at 0.050" numbers it's a good idea to see what the 0.200" specs are. And, the advertised specs are still important, tho harder to quantify with there being no industry standard, since valve opening and closing events are specified at that point and the lash ramps can vary how the profile begins its approach to 0.050", also.
Of course, for those who want more detail you could check the specs of Cam Dr or Cam Pro Plus files on the cam(s) in question. Then there's Perf Trends' Cam Analyzer w/test stand setup if you reeealy want to see what you've got in your hands.
For most of us, the 0.050" numbers will suffice
Last edited by TheSkunkWorks; Jan 13, 2008 at 02:08 AM.
