MopaR&D said

Hell yeah, this is the kind of explanation I was looking for when I asked you a few pages back.

A few points, and I'm just trying to have a convo here not claim you're wrong at all... first, the included valve angle on the G3 is much narrower than the G1 and G2, I think it's around 35 degrees instead of 58. Is it possible that would reduce the tendency for the excessive overlap flow since the air is flowing at a more downward angle into the cylinder? I also think that's partly where the dual-spark-plug came into play; there was no room left between the valves and just putting one plug in would have required it to be really far off the center of the chamber. The dual plugs also give the "extra" benefit where G3 Hemis require very little ignition timing advance for max power, as in 26-28 degrees. I dug around the web a bit and found an interview with an engineer who worked on the development who said they actually started with the air-cooled 2-valve Porsche combustion chamber as opposed to the previous Chrysler Hemis and worked off of that. Filling in the chamber on the sides of the valves further reduced chamber volume and provided some quench area without shrouding the valves and also allowed for flat-top pistons with good compression ratios.

One neat feature of the G3, the stock pistons have a slight dome in the center. When I was in grad school I took a class on fluid dynamics and had access to SAE publications; I did my final project on air flow through the modern Hemi engine and found the original article submitted to SAE by the Chrysler engineers at the time (late 1990s). They explained and showed through CFD cross-sections that there was significant flow going down the side of the cylinder by the intake valve and putting a slight dome on the piston increased the intensity of the tumble flow and allowed that air/fuel to continue mixing throughout the intake stroke and for much of the compression stroke. Swapping to true flat-tops takes away most of the tumble flow which is probably better for max power since less kinetic energy of the flow is "wasted" due to turbulence.

Regarding the valvetrain, apparently the designers consulted with Tom Hoover and Willem Weertman (by then in retirement) who worked on the G2 426 and they recommended raising the cam tunnel to shorten the pushrods and improve geometry. Which they did and also did a lot of Finite Element Analysis on the rockers, springs, retainers, valves to make them as light as possible without sacrificing strength. A few years back when I was looking at building up the 2014 5.7 I have, everything I was seeing from the guys who were building them up confirmed the stock G3 valvetrain is good to 7000 RPM at least. You mentioned you haven't seen one spin that fast though so jury's out on that one I suppose.

And then the skirted block, I think that had more to do with NVH like you said regarding the LS and also carrying over a strength feature that had proven to work in the past. I think now it's known there are stronger and better ways to beef the lower structure than deep skirts and cross-bolted mains but in the 1990s it probably seemed like a good idea for a production engine where 8k+ RPM windage wasn't really a consideration.

Being an engineer, someone saying "it can't be done" is the biggest motivating statement one could make lol. Now more than ever I want to build my 5.7 to make 600 N/A HP, or at the very least 570 to hit the 100hp/Liter mark all the import guys look down on pushrod V8s for lol.

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