Compression Calculator accuracy??

[365Jeep]

Okay, first post here, and I know there is more information here than I can comprehend, but I have been playing with the Compression Ratio Calculator here. I've also been playing with Dyno2003, and I've found a couple of inconsistencies I would like cleared up.

When using the Compression Rate Calculator, there are differences between the Intake Valve Closing Angle in the default cams versus the same cam listed here http://www.angelfire.com/my/fan/Jeep4.0Camshafts.htm. For example,

1) Comp Cams 115 has a VCA value of 44 on the calculator versus 48 on the website.
2) Isky 1331M has a VCA value of 52 on the calculator and the same value on the website.

I can see that the calculator here shows a 4 degree advance on the Comp Cam, but does that mean I should install it that way, or is the advance "built in" the cam from the factory?

So the real question is, is it safe to simply enter the VCA from the website into Dyno2003?

David

[Cheromaniac]

I can see that the calculator here shows a 4 degree advance on the Comp Cam, but does that mean I should install it that way, or is the advance "built in" the cam from the factory?

The advance is built in from the factory so use the ICA figure from my site.

[Muad'Dib]

The calculator itself has been proven to be very accurate, however some of the figures for the cams may not be. I have expressed in the past that if there are any corrections that need to be made then I will make them. One thing to also keep in mind is that most people use @ 0.050 figures versus the advertised values which is what the calculator expects to see.

When talking about cam "advance" the built in figure must still be entered into the calculator. So for example if the cam has 4 degrees built in then you need to add that figure to the calculator. Additionally, if you want to advance it more to say 2 degrees over then you would enter 6.

Hope that helps.