How do you read cam specs? What do the numbers mean?

[crazybiker]

I've been reading a few threads lately, and a few people have posted some cam specs, and I've been urging to know what they mean exactly.

For eg: "280/286 .612 .615"

I got that out of 'DARTVXCLUBBY's' thread about his new LS1.

What do those numbers mean?

...and if possible could I get a medium description to, rather than First number means this...only if possible though.

Thanks

[delcowizzid]

intake valve open duration/exhaust valve open duration . intake valve lift/exhaust valve lift

[delcowizzid]

and the duration is degrees of rotation in crank degrees not cam

[VT-565]

I wonder if that lift is at the lobe or at the valve? surely has to be at the valve.

[delcowizzid]

it will be valve lift

[VT-565]

Ok, just to further answer crazybiker, on most cam cards, they will specify lift at the lobe then lift at the valve, obviously lift at the valve will be determined by what ratio rockers you have, they will specify what ratio they used to arrive at valve lift figure too.

I'll post mine up later, my cards at home, It's a monster
I might even try scan it to give you an idea what they are on about, mate.

[greenfoam]

I'm going to have to write up that cam spec how to I was supposed to write over Easter, it's pretty complex but I'll try my best to explain everything so you can keep comming back to it as you figure out more and more, the most important figures are the intake and exhaust timings at .050 inches, advertised duration doesn't mean alot

[delcowizzid]

yeah you mean that cam thread you started ages ago and never got back too LOL . the .050 figure allows for the ramp rate of the lobes .with all the figures you can work out anything you want

[VT-565]

cam is the brain of the engine. very important to get it right or close to it.