900HP wrote:He also says: The chart in the book uses valve size only to calculate seat velocity, when D.V. uses "cam master" it uses actual flow. The assumption in the book is that you have a valve and seat arrangement that has a standard flow like an off the shelf head you would normally get from a catalog. The Dart heads in this build have an older 45* seat from a "cup car" which was highly sucessful and popular back in the early '90's. These heads have approximately 7-10% more flow in the range during overlap and therefore the valve appears to be much bigger to the engine and hence the wider seperation.
when I wrote my cam calculator I tried to take Vizards chart and "math it out" so I could write the program. It called for a tight LSA of 107*... now if I read the chart correctly that is what it should have run. And as most here noted, including Jones, Vizard went way wider than expected.
Three things could be wrong here (or a combination of any),
1: I did not correctly read that chart (I doubt this),
2: the calculator selects the cam that will best match the head / ci rpm range and because they were going for more RPM than the heads called for with that ci he went with a wider LSA to bolster an extended RPM range.
3: as noted, the Vizards cam program uses flow instead of valve size to calculate LSA
now if it's number 3 primarily why push the valve size to select LSA b/c most anybody using this formula probably has a pretty good idea what their heads flow.
I would like to ask both Jones and esp Vizard if this was going to peak at 7k and not worry about carrying the RPM to 8500 what size cam (and mostly LSA) would have been selected?