cam confusion on Potterman's site?

[tberk@mindspring.com (T Berk)]

> Jeff Toomasson wrote:
> 
> I was cruising through Potterman's site and noticed he offered two
> Solid Lifter 8v cams.
> 
> A Neuspeed .432 lift, 272 duration for "Hi-Performance" 

but what of the lift?


> and a Neuspeed
> .425 lift, 283 duration for "street performance"
> 

This one has longer duration but less lift than the 1st one.

> Aren't these terms reversed? Wouldn't a 272 be "milder" or "less
> radical" and thus more suited for the street?
> 
> My limited knowledge of the difference in cams was the duration -
> could someone explain this? TIA
> 
> Jeff
> _______
> 


The cam is a profile; it's a two dimensional oval that includes (but is
not limited to) total lift measured at (only) one point & duration (how
long the valve is held open). There is more to it because the profile
isn't a sharp switch ON, switch OFF type thing, it's a trip through the
tulips around that cam lobe. Stuff like how fast the ramp up to full
open is and how long it stays there and stuff, like that kinda stuff.
You know- stuff.

Tuning these things is an art to match it to the amount of cylinder
volume and how fast the things can fill and evacuate spent combustion.
How they did it before CAD/CAM computers is a wonder.


TBERk