Don't understand cams

Cudafever said

so Intake opens at 19* btdc and exh close at 13 atdc. so my math says that i only have 32* of overlap. Now these ## are a @.050"
I realise that i'm comparing apples to oranges here but, that is only half of the overlap, of my smaller cam.
Now i'm sure that they differ because of the gross and @.050" But over 30+ degrees.....less???

Click to expand...

Your math is right but overlap has to computed at advertised durations, not .050" durations. I'd expect the overlap to typically compute out to 40-50* higher (or 50+* with a slower ramp cam) using advertised valve timing versus .050" valve timing, which reflects almost directly into the overlap numbers. So, yes, that's not comparing the 2 cams properly; don't do that LOL.

Go to some data sheets like the Crane or Lunati catalog pages, where they show numerous cams in a page listing format, and you will see the 40-50 degree difference in advertised versus .050" durations. For the Lunati catalog, you'll see the general overlap numbers vary to some degree by family of cams.