The reason the engine is as big (in displacement) as they have made it is so that it can achieve maximum efficiency with the given tune and operation range. The new 7.3 is being designed to run in the real-world, daily-drive range (well below 4k) and to run at true stoichiometric A/F mix as opposed to the industry standard of letting it get down as low as 12.5
In short, it's supposed to give you fat power/torque for workloads but also be relatively light on the fuel bill.
So like a typical big block. True stoich is the industry standard, it’s the basis of closed loop. Big blocks don’t need as much throttle to move about as opposed to a smaller displacement/boosted applications so they won’t necessarily see 12.5 on a commute as often, but they still will under high load/WOT situations. There’s no way around it.
Light on the fuel bill is relative. Big block fuel consumption tends to remain pretty much consistent no matter how aggressively or miserly it’s driven or the load, but it’s not necessarily good mileage.
Though I like the 460, it probably couldn't hold a candle to this new 7.3...
For starters the 7.3 is very well packaged, fitting 445ci and variable valve/oil tech into a space technically smaller than the 4.6/5.4/5.0 design. Head and piston tech has come a very long way since Ye Olde 385 Block, allowing for higher compression and better quench/flow/swirl, and with modern EFI ignition timing is spot-on perfect in the high-advance range (which is where this engine is being built to live).
Regarding weight, I'd wager this new engine to weigh the same or less than the factory 4.6 in our MN12.
The 460 is smaller than the 4.6 too, OHC and Hemi head V8s were never the paragon of space efficiency, the block and crank contains the bulk of the weight and to achieve this displacement it simply requires more iron/steel/aluminum. There’s a 60lb difference just between 4.6 and 5.4 bare iron blocks, all in deck height.
It’ll be lighter than a 385 series because of the aluminum heads and plastic intake of course, but there are aftermarket aluminum heads and intakes for the 460 too, which simultaneously bump compression and have that better quench/flow/swirl to boot. Port EFI intakes are widely available as well.
ALL THAT BEING SAID.....
I do believe there will be a huge performance potential for this engine once folks figure out how to change the cam (and variable timing) and most importantly the ECU tuning. I can't speak for the head/runner design as it's a 2V setup and, though the ports are large, designed for low-end grunt along with the wrapped-up intake manifold runners in the valley, but I'm sure someone will figure out how to boost the snot out of it since the bottom end is being built very robust (was there any mention of the crank being forged?)
I’m not saying a 460 is *better*, as there are of course inherent advantages to a truly modern design, but as a swap candidate into a car like a MN12 the pros and cons of either one will cancel each other out. The pro for the 460 is the blocks are cheap and easy to find and have a good selection of dedicated speed parts available for it. The 7.3 isn’t even out yet, and if swapped into a car in stock form it’s not going to be a great performance motor for it until the aftermarket catches up.
