Domeskilla is right- most vtec systems are 2-stage (hi and lo) but the s2k and the d15b and i also believe there was some other jdm motor (like a d13??) that has the 3 stage.
Now, Overlap is controlled by two things- the cam profile, and the degree of the cam gear. in other words, its all cam.
Overlap is good for one thing- making high rpm power. when you are spinning at 8000+ the time from open to close gets smaller and smaller due to the fact that the time it takes to open and close gets less and less. with a longer over lap, the top end is not killed, because the duration keeps the valve open longer even while moving super fast.
On a boosted car, overlap sucks. under 8000-ish, a lot of your air will simply push itself right through the chambers... out the exahust valves that are still open due to the cam, and never combust, thus impeeding your power potential. with a near stock overlap (such as a gsr cam's duration), little to none is leaked out, thus giving you the air in the cyl. to make the power- the whole point of a turbo in the first place.
the ideal cam for turbo is one that has a good lift (opens the valves high) at a near stock duration. thus, it allows a LOT of air to get in and out, but the time it is open and closed is not made longer.
This goes for ANY cam style... VTEC or NON-VTEC.
Now, back to VTEC vs. Non-VTEC... Why is VTEC advantegous?
By offering 2 (or more) lobes, the car can make bot good low end power, and still have a good top end.
Think v8's for a min here. they use a small cam for great torque off the line, but are dead at 6000 rpms.
sound familair? yup- the LS is the same way.
and you know what, so is the GSR, ITR and so on--- until it switches lobes. the cam profile of the low lobe is good for 5000 rpms, and then its over.... hello vtec, swap over and lock the middle lobe, and suddenly we are on a larger cam- one that wucks balls in the low end, but has a little more duration and lift for better top end power.
Ok, so now all the non-vtec whores are saying, ok- but why not just run a big cam (say, stock gsr vtec lobe specs) in the LS.
you can, but like i said above, your low end is going to fail- at least as far as power is concerned. you will have no torque until 5000 rpms, just about when youd hit vtec to go to the larger lobe that a vtec setup offers.
As for "I like the non-vtec due to its low end torque".
Well, let me tell you something. BOOST is your torque. Stop thinking like an all motor guy. This is the boost forum
Jeffie7 has a boosted b16a. at 2500 rpms, he has well over 100 ft/lbs at the wheels, as dyno proven.
you won't see 100 ft/lbs on even an LS until at least 3500+ and probably close to 4500 on a more built setup.
here's wildbill's LS dyno. P&P head, b16 pistons, crower 403 cams.. all motor, yes... but i'm just using this as an example.
ok, now notice what i said... its just around 100 from 1000-3000 and then slowly goes up in torque till it flattens out.
now, lets take a look at jeffie7's boosted b16 dyno.
Got torque? it just fucking climbs.... and that's before the vtec engagement of 5200-ish. That is what boost is all about.
so stop thinking like an all motor guy, and start thinking like a boosted guy- Air flow = power.
size, really doesn't matter.
On top of ALL of this:
-the LS head FLOWS like shit - air flow = power
-the VTEC bottom ends have oil squiters which help reduce heat and detonation on a boosted car.
and i could go on for days. but going back to m y frist post. there IS NO arguement. VTEC is a better technology, and will alwyas make more power- na or boosted.
however, for the inital cost of about 2000 less, the LS motor has great potential for a guy on a budget just looking for a little more umph... and not a 10 second car.