In the article by David Vizard, is a great piece that I enjoyed very much. I am very interested in high performance hot rodding as I think there is always room for more people to know more about. The article July 06 Be The Camshaft Expert, David refers to a chart to determine overlap, I cannot find a chart to determine the overlap that he refers to. I am not sure if it got overlooked or that I am missing something. I even looked on your website and its not there either. There is an estimater chart but not one to come up with a number of 66 that David came up with. I am planning on building motors over the winter and am always looking for more info besides my engine machinist. I apreciate all the tech articles and even the in dept technical stuff. Even if some dont like them I think you should keep on reporting on the technical stuff even if it is for the few and not the masses. I do also enjoy the other articles on stuffing too much motor in any car or handling or even the rods most of us could only dream of. I even like the chevy vs ford vs mopar vs ?, if all cars were made by the same manufacture it would be boring thats why we need different brands thats what makes hot rodding. I currently have a 67 firebird w/455 95 chevy caprice w/lt1 350 and 373 gears 73 chevy pu 4x4. I guess you could say that I enjoy GM stuff. I also have a 82 mustang and a7.66666 that I am thinking of putting in it for fun. I enjoy reading your mag, Thank You for the great articles and keep up the techno stuff, Yours In Christ Bartly at Spokane Wa.  

I don't think it was overlooked, Vizard doesn't give  a formula for determining overlap, that is why his pie chart is simply called an "estimator."  

The formula for figuring overlap is: adv. dur.-(2xLSA)
ie:
280 degrees advertised duration
110 degrees LSA, LDA, or LCA
280-(2x110)
280-220=60
60 degrees of overlap  

Hi,
The formula for figuring overlap is: adv. dur.-(2xLSA)
ie:
280 degrees advertised duration
110 degrees LSA, LDA, or LCA
280-(2x110)
280-220=60
60 degrees of overlap  

I have found that 206/206 @ .050 works well. I run alot of computer simulations. The one I'm working on is a 206/206 cam, 112 LSA, with Rhodes lifters to put me at 196/196 @ idle. More power, more mileage, excellent idle. Tell me what you think. 196 is stock by the way.  

Works well for what?

The reality is that the ideal cam only exist for ONE set of circumstances-- rpm, displacment, head flow, compression ratio, etc.  So the minute you change a single variable, you've now gotten away from the ideal.

To my mind, the peak tq usually represents the point of "ideal" for most combos, and the RPM and amount of grunt present tells a lot about the combo.  The trick to keeping high HP is to have the tq curve fall off at a rate slower than the RPM is rising, hence you actually gain HP.

Keep in mind the formula for hp: (tq*rpm)/5252.  This tells us that if tq goes up and rpm is constant, we gain hp.  We also gain hp if tq is constant and RPM goes up.  If we can get both to rise at the same time, then we have rapidly rising HP.

jh