I'm seriously not trying to be confrontational and say you're wrong, you're not.
I'm perfectly familiar with typical ICE and the design of jet engines. Exhaust is no less important in ICE. If you block it, the engine doesn't run.
Jet engines use exhaust as propulsion, so it just moves the mechanism from inside to out, in a way.
A muffler is a device that baffles air to quiet it. That's -exactly- what this device does. You can argue, rightly, that more is at stake and more considerations must be made here. But it's still, by definition, a muffler.
Exhaust systems on ICEs are much more than simply a muffler and directing exhaust gases away from the driver.
Exhaust systems can be tuned, as in using wave propagation to scavenge the exhaust gasses out of the combustion chamber much more efficiently. Intake manifolds are tuned for the opposite effect. The dyno tests on my Dodge V8 showed adding a 3/4" spacer between the carb and the manifold added 40 HP at the peak power rpm.
As someone with lots of experience on small block Fords, but nothing Chrysler, I would say that a 3/4" spacer under a 600-750 CFM double pumper adding 40 HP just solved either the manifold leak or the throttle cable binding. Did peak power occur at the same RPM (i.e. was it really putting out more torque)? How fast was it spinning, and at what RPM did the power really start dropping off?
Was this measuring at the flywheel or at the wheels? I'm genuinely interested, it's been a long time since I've had grease under my fingernails.
The engine had just been built and I took it to a dyno company to be tuned. It was mounted in their machine, so it was at the flywheel.
The guy doing it remarked that it really made a dramatic difference, it seems the original parts configuration was a pessimizer. I'm not too surprised, because the engine was heavily modified and so would exhibit very different flow characteristics from the stock configuration.
I don't remember the RPMs. It's a bored, stroked, and rollered 340 engine, and peaked at just under 400 hp. The dyno guy normally worked with drag engines, and told me I was an idiot because I had the stock heads modified rather than getting aftermarket performance heads, a mistake that likely cost me another 40 hp.
The engine was built as a sleeper, so the only way you can tell there's some monkey business going on is the oversize aluminum radiator, but nobody notices that :-) But they notice when I start it.
Sounds nice. Yeah, a lot of engines of the era were detuned at the factory for regulatory and other (supposedly e.g. insurance, later emissions) reasons. If you already had other top end mods, e.g. good headers and ported heads (seems you did) then sometimes a small change could open up a bottleneck. Thanks for sharing!
I always found it all interesting. We've all heard of 'hemi', but now pent roof across the board, that found adding just the right amount of turbulence on the intake side led to power gains.
Also on exhaust side. Too big of exhaust, such as 'open exhaust', is worse in most cases than restrictive. Apparently a restrictive exhaust provides both accounted for backpressure, and at times a bit of a vacuum effect.
Anymore, I just trust the makers know what they are doing and go with it. But 40 years ago, very different story. My 2019 Colorado would outrun my old 66 mustang, both in stock forms.
I'm perfectly familiar with typical ICE and the design of jet engines. Exhaust is no less important in ICE. If you block it, the engine doesn't run.
Jet engines use exhaust as propulsion, so it just moves the mechanism from inside to out, in a way.
A muffler is a device that baffles air to quiet it. That's -exactly- what this device does. You can argue, rightly, that more is at stake and more considerations must be made here. But it's still, by definition, a muffler.