Originally Posted by therieldeal
well then we essentially have negative overlap is what your saying? Intake and exhaust are never open at the same time?
That wouldn't surprise me on a stock cam or a small 205 @ .050 size cam. Stockers have minimal overlap for the sake of emissions. A 205 is a conservative grind, so a minimal overlap doesn't surprise me there either.
The '94 to '97 exhaust cam has a similar duration (205 @ .050) but not as much lift. This is why the "exhintake" cam swap is common (that and it is cheap). Your increased lift on both cams should certainly show some flow benefits over the exhintake mod.
And don't worry that I called your cams "small." Turbos like larger than stock cams a little but don't go well with really big cams. It comes back to the overlap problem. But hey, since you've run the numbers and the overlap looks like a non-issue, I think you will be just fine. I would start with them "straight up". Then later I would definitely dyno tune those cams in for the max benefit. Having better cams may raise your rpm range enough to make you happy without retarding.
And yes, retarded intake cams remove low-end torque and shift the torque slightly up the rpm range (200-400rpm). Not only is it common engine builder knowledge, but I've simulated it enough on the computer program "Desktop Dyno" to make anyone a believer. (BTW my '68 GTO has a cam with a duration of 231 intake and 240 exhaust @ .050, which would be terrible for a forced induction application, or even a small displacement application. Also, Miata heads flow so much better that the valves don't need to be open so long to make good VE numbers.)
As it was stated with regard to "advertised duration" numbers, they are measured differently by different manufacturers. I know some are measured at .006 lift and some at .001 or even a few at .010. Numbers at .050 are a standard that is universally accepted and always published, so they are the best measure of apples to apples.