Wait, so you ask for my opinion then you argue?
Let’s be honest here, if any engine was overrated, it was the 4.6L 4V in the '99,'01 Cobra. None I've ever seen, or heard of have ever made their advertised power levels. As a matter of fact, they’re renowned for not producing them.....even after "the fix". They generally put out no more than 250-265rwhp, which is 15-30hp less than the advertised specs. The Mach 1's dyno slightly higher than that, with a 5-speed coming in at around 265-270rwhp. The '05-up 4.6L 3V's regularly match those horsepower numbers right off the showroom floor.
The same goes for Forced Induction numbers. The stock 2V’s aren’t even close and the 3V's and 4V's seem to be on a pretty even keel across the board when you put the unnatural motivation to them. Even when you start really pushing them (15psi+) the 3V and 4V cars always seem to be within 10-20hp of each other with any dyno comparison I’ve ever seen and even that 10-20hp can be attributed to many different factors.
But hey, you don't need to take my word for any of it, just head over to the S197 section and see the dyno figures for yourself. There are plenty there that have put them on the rollers.
I’m not sure why it matters how many 3V's and 4V's are competing in NMRA. It's irrelevant to the subject at hand. The 4V's have been around for 17-years and used parts are readily available and cheap.....not to mention the 2V/4V engine swap is a whole lot less complex and expensive by than the 3V, so it’s no surprise many people are running them. By comparison, the 4.6L 3V has only been on the scene for 5-years, yet it has a larger aftermarket following than both the 2V and 4V engines. That speaks volumes about their success.
As far as their heads go, I'm not saying the 4V heads don't flow more air, but you sound more like you're wrapped up in peak flow figures and seem to ignore low lift and average flow numbers, or volumetric efficiency. The very fact that the 3V's are making the same kinds of numbers as the 4V's with one less valve and 2-less cams is a further credit to their design.
And yes, the
NEW 5.0L 4V heads seem to be the best designed of the bunch thus far.....but the comparison I made here was the success of the earlier 2V and 4V 4.6L engines in comparison to the current 3V 4.6L engines. Quite frankly, the only 4.6L 4V head castings that have any advantage at all out of the box over the 3V castings are the later “C” heads found on the ’03-’04 Cobra’s and Mach 1’s. All others have fallen short either with flow, or low speed velocity potential by comparison.