.....another thing that they did to accelerate the opening is they went with 1.7:1 ratio rocker arms. Not only accelerates, but also increases lift, thereby changing the dynamics of the cam lift/duration specs with out getting really radical of the base circle.
I'm not a really good person to answer those questions, I'm not really a cam expert, just have a good understanding of the theory and mechanicals involved.
I'll take a stab at it though, and I'm sure somebody will correct me if I'm off base.
The lope you mentioned is probably the overlapping of duration between the closing of the exhaust and the opening of the intake. The dynamics going on in the compustion chamber are such that as the exhaust gases exit, the intake valve is opening, the exiting gases actually produce a lowered pressure condition inside the cylinder that helps draw the intake charge into the cylinder, while the exhaust manifold or headers help draw the exhaust gases out.
I may have answered your next two questions by answering your first... not sure.
But on the emmissions part, I would venture to guess that is taken care of by utilizing the computer to control the timing of spark, fuel, and amount of fuel or fuel/air ratio.
The O2 sensors downstream in the exhaust, and the MAF in the ari intake path collect information and feed that to the ECM, which in turn controls the timing and varies the air/fuel mixture many times / second. Since this is real time information that changes as needed to produce the most efficient burn, I'm sure that's how we can get so much HP and still meet emmissions requirements.
That is something we couldn't do before computerized ECMs came along. On carb. engines the best that could be achieved was to jet the carb for average conditions, and accept the less than efficient results when the conditions were not "average" as the system was originally set for.
Did that come close to what you were looking for?
Ya, for the most part, I know about the PCM, and I guess the the LT4 HOT cam is pretty clean,(and I actually have those emmission numbers) and that has a pretty good lope to it too as I recall now. The more I think about it those smooth idles must just be for driveability and comfort issues for the average consumer. I'll take the lope! It definately adds more to the experience! Don't you Think?
Yeah, a nicely cammed engine sure does give distinct personality to any car. The LS6 engine actually has the highest lift cam ever placed in a production Chevrolet engine. I think it idles so smooth because the idle speed is 800-850 (at least on my car), it would probably be a little rougher if it was down around 550 - 600 or so.
I have seen cams that need 1200 or better just to idle.
Now you got me, I have no idea. I would guess that the spring rate would be OK, but I don't know about the clearance for the piston at TDC, and other issues that a higher ratio rocker would bring to the LS6. I don't know how much room the rockers have in the rocker arm covers now either.
Maybe someone else will jump in here with more knowledge than we have as they get home from work or play.