I was looking through the summit catalog and I saw section of cams made for nitrous applications. I was wondering what makes a nitrous cam a nitrous cam? How does it shift the power band around? What makes it so special that it would have its own little section?

 

If you start with what would be a good NA cam for your motor and add some exhaust duration plus a bit wider KSA you will have a good cam for using nitrous. The added exhaust duration is to accomodate the additional volume of exhaust gasses when the N2O is activated. More LSA is needed with the bigger exhaust lobe to avoid excessive overlap.

Rich

 

They are a ground on 114-115 so you don't blow all the nitrous out of the exhaust ports during the overlap while both vavles are open. Big time nitrous cams would not net nearly the same as if you had a N/A cam. With nitrous being your primary power adder.

 

Overlap considerations for N2O are different from a blower car. Nitrous is not "forced induction", it still depends on some overlap to get good cylinder filling. Since the intake tract is not under constant positive pressure (as it is in a blower car under boost) a moderate amount of overlap is desireable, certainly more than in a blower car. That's why for a given duration you will typically see overlap like this: NA>N2O>SC as reflected in the LSA. In terms of numbers, typical "hot" street strip roller SBC cams will have LSA's in the following ranges: NA: 110-112, N2O: 112-114, SC: 114-116. It's always a compromise and many different combos can work. What really counts is the valve timing, so it's always a little misleading to talk about LSA in isolation.

Rich Krause

 

The nitrous cams provide additional exhaust duration to avoid pumping losses from the additional exhaust demand while on the dope.

Select a similar pattern nitrous cam as you would require for your application.

Expect to lose 20 or so hp with a nitrous cam on the motor. But the potential gains on the hit are tremendous. David Vizzard claims an 80hp gain on a small kit.

If you don't already know who he is pick up his book on "Building Small Block Chevy Motors on A Budget." It's a collaborative effort of his life's work. There is a section on this very subject. It'll be the best $20 you ever spent, and it will single handedly save you thousands of dollars in component selection.

 

You wouldn't mean I would lose 20 hp vs a stock cam?

 

No sir, it would be from what a similar patterned cam, without the extended exhaust duration, would produce.