I've been researching Bernoulli's principal and looking at ideas for better ducting on these cars.
Basic idea is that air is lazy. REALLY FREAKING LAZY! Probably lazier than your 13 year old nephew.
The basic problem is that with these cars and how they are designed, it's a packaging nightmare that destroys the radiators efficiency because of the fact that air is lazy. Laymens like ourselves see a few sets of numbers or ideas and apply it when physics tells us something else needs to happen. Case in point is the front end design and access to fresh cool air. We might logically conclude that having as much grill opening to the radiator as possible is our best bet.
This is hurting us in actuality. For most of our cars the front end inlet sizes are larger and provides more air exposure to the face of the radiator than the area of that radiator face. Often, the entirety of the front end from the grill to the radiator core support is open. in many cases there are other openings from the core support area to the engine compartment that allow air to flow without passing through the radiator core.
Remember, air is freaking lazy and will take the easiest path it can find.
If we look at modern vehicles, many of them have very small grill openings and often there is specific ducting that is directing that air to the radiator. Based on Bernoulli's principle, in most cases the inlet should be somewhere around 1/3rd the area of the core. This reduces the velocity of the incoming air as the volume increases from the inlet to the core, creating high static pressure on the face of the core.
Without this ducting, we don't get nearly as much pressure increase at the core. The air just kind of tumbles around and looks for some other escape vector instead of through the dense radiator core. Having a radiator with lots of cores and lots of fins per inch actually makes this worse!
On the back side of the radiator, we want to create the opposite, a reduction in static pressure, but an increase in velocity. This acts in the same manner as scavenging does in your exhaust system. Basically making physics force air to stop being lazy and go through the radiator.
In many cases, we don't have room behind the radiator for proper ducting and we're using a puller fan (mechanical or electric) to do the job of increasing the air velocity. The next problem here is that the fan is slamming this column of air directly into the engine and from there into a hot engine compartment with little to no real venting taking place. This has the effect of creating pressure on the back side of the radiator, reducing mass air flow through the core/s. It also increases drag on the car itself. It's interesting to note here that Pontiac design engineers knew this and started implementing strategies on the 69 TA and in later TA's that had fender extractor vents. This not only aids in cooling, but decreases drag.
So, what can we do? On a first gen f-body specifically, the hood latch upright presents a massive space limitation for getting any real type of ducting to work here. I think you "could" model an inlet box that has a foil in it around the hood latch, but it would be pretty complicated. If this piece was removed entirely, there's plenty of space up front to have a proper air inlet mounted that seals to the core support. This would however require the removal of the hood latch and associated hood and valence modifications that would come with removing that piece.
Having one side of of the equation is still better than none of it.
But what can be done about the reverse side? From a ducting standpoint, probably not a lot, unless you move the engine back, or the core support forward. What you can do is provide cooling vents to the hood and fenders. While the placement of the 1969 Trans Am vents isn't optimal, the fact that it has a fairing over the actual vent creates a high pressure zone that sucks air from engine bay. Likewise if you added vents to the hood with gurney lips at the leading edge, you're also creating a high pressure zone that will relieve hot air from the engine bay.
I've observed this with my car in that with the hood open, I can't get the car to creep heat, even in upper 90 to 100 degree temps. That tells me just how much effect the hot underhood is having on my cooling system.
Now, all of this is a lot and for most people really overkill, unless you're doing the silver state classic.
Practically then, what can we do? We need to pay critical attention to the seal of the radiator against the core support as well as any passages from the front of the car through that core support. The more we do to seal the front end to force air through the core, the more efficient it's going to be. Even if not originally equipped, I also believe that the upper radiator close outs are not an optional piece (unless the hood seals to the core support) as well as the lower closeout that incorporates and air damn. That air damn is positioned on nominally the same plane as the back side of the radiator, and is creating some of that low pressure zone needed to help air move through the core.
We also have to take care that the radiator is sealed to never allow hot underhood air to circulate to the front of the core, further reducing cooling efficiency. Additionally, the shroud in use needs to "see" the entire core. In my case, I use the Flex-A-Lite black magic fan that is only 22" wide and 17" tall. For my factory sized radiator that is 23" wide and 16.5" tall, I end up with half an inch of exposure to the hot underhood air, instead of the fan drawing air through the radiator only, as well as 4.2% of the radiator that at a stand still, is doing precisely nothing, as it has no air flow at all across it. In fact, considering that the rear most tubes would be subject to hot air from the engine bay, it may actually be hurting things.
I've mentioned it before, but my one complaint about the Cold Case radiator is that it sits a bit more than an inch from the core support. That area is subject to the underhood air being drawn around to the front of the radiator, further reducing efficiency. These areas need sealed up a much as absolutely possible. In fact, I would go as far as to say that, I'd take the radiator off and clue foam around the back side of the core support where the radiator mounts, that way it completely seals off the engine bay to the core.
In my case at least I think there's a solid 5-8% efficiency increase to be had just with those items. But, I think that what I'm learning with some research and my observations is that what we think we should do to help keep these cars cool, can at times exacerbate the issue if we don't first take care of some of the minutia.
