Split Duration

[phoenix64]

Ok whats the deal on duration. Our cars come stock with a split duration cam. You would assume that GM did this for a reason. So why are some people picking cams with single duration. I'm confused. I know that a good nitrous cam has more exhaust duration. But the stock cam was set for N/A performance so why does it have more exhaust duration. And yet people are picking cams with single duration of N/A use. I'm confused.

[pgriffith]

Well if you look at the stock cam specs you will notice that the intake side has more lift then the exhaust side. So even though the exhaust has more duration its not really being favored all that much because it has less lift. And as far as having the duration a little fatter on the exhaust side it might be because of our tiny exhaust manifolds and it helps scavage the gases out of the engine.

[phoenix64]

Ok so is a single duration cam better for N/A power then?

[phoenix64]

Anybody else got any sugestions, or a place where I could learn about cams? I get duration, and lift, but what does lobe seperation and intake centerline get you?

[Arctc Wolf]

If you have a low-restriction exhaust, then u might be able to run the same specs on both intake and exhaust valves. i'd run more duration on the exhaust since the exhaust valve is smaller than the intake valve.

[67-03 RIP]

[QUOTEAnybody else got any sugestions, or a place where I could learn about cams? I get duration, and lift, but what does lobe seperation and intake centerline get you? [/QUOTE]

Try all the different cam company webpages (Lunati, Crane, Comp, etc) I think some of them have decent FAQS/Tech on lobe sep/centerline.

Ron