What you are talking about is what I call "exhaust blowdown".   Putting a steep ramp on the opening side of the exhaust, running a fast rocker, and then a slow closing side to kill some valve speed on the closing side generated by the fast rocker arm.  I never had any luck with running the intake way ahead in anything FE.  The further apart the lobes are, the later I like to open the intake valve.  Wide centers on a street stroker would need low compression to avoid detonation, in my opinion.  Also, heavy street cars will pull better with tighter centers.  I do try to get all of the blowdown I can when the exhaust valve opens, and then let the header pull it through a slow closing side.  Some of this kind of theory is unfortuneately only proven through extensive testing...........which requires huge amounts of time and money, or seeing trends over time.  I have to go with the trends over time, because for some reason I never seem to have huge amounts of time.....or money, LOL.

How would over-scavenging show up on a dyno?

Flattening out on top and showing rich maybe?

Certainly no criticism on the motor, Blair does great stuff, but I have been considering how more lift/less duration on the exhaust side would work out.

My thought is, for these big ones, keep a constant overlap value (in my case for drivability) but instead of big exhaust duration, add intake duration for power but make a shorter, taller exhaust lobe that flows enough but shuts the door early.

Although I haven't figured out a way to calculate what the motor might want, it seems to me that especially with a very good header design, adding exhaust duration could  eventually overscavenge.   

The second phase to that is, if it is overscavenging and a quick and tall exhaust lobe will fix it, may as well get a little more intake lobe to make some additional top end power.

I noticed Kaase was doing it on his EMC Hemi motors, which are known to overscavenge with too much exhaust duration, but how would we see it on a dyno to know if a wedge was emptying the chambers?

We were dealing with a 60% flow ratio exhaust to intake.  In my world, the lobes I used are "endurance" lobes.  This thing should make alot of laps and some street miles with no trouble.  I would have approached it differently if we had brazed the floors in the exhaust, and/or had a real aggressive camshaft.  I was using the split duration, tight centers, and the header/collector to crutch the 60% exhaust problem.  My gut tells me that it would be hard to overscavenge this combo.  If it had 75-80% exhaust ports, you would have seen a much different camshaft.  I also had pump gas on my mind.  The cam being pretty mild on the intake side, I tightened the centers to take some of the bite away from the DCR, which was fairly high for static of 11.3.  I know the DCR calculators don't address the separation, but more overlap will reduce the tendency to detonate at lower rpm.  Many factors led me to make the cam like this, and it did okay.  R&D with no budget constraints could no doubt produce better results, but I had no 500" road race TP data to draw from, so this was square one.......

I'll bet you are..............I could use 10 or 12 myself, LOL.

  The most fun I have had in a while!  I could not explain about 50 of the hp, but that was a good kind of problem.  We honed those engines a little different, and those 660 carbs were really good for the combo.  We tried a worked-over set of 750's and lost about 10 hp on the 511.  This is my first post on this Forum.......looks like a good place to hang out!!

BP