Is this a fair radiator?
That is A/C AND CAP combo.
Guess that combo could generate some heat.
Also note the WP impeller is smaller dia and there are fewer vaines and the fan has wider blades. My guess is that are spinning the fan faster with a wider blade moves a **** ton of air. The smaller impeller and fewer vaines seems like it would push less water so maybe that was their way of keeping water flow about the same but increasing airflow.???
I also found it interesting that the majority were underdriven by 5 percent.
Yes! This is important stuff to recognize. This is why you have to pay attention to the entire cooling system, not just the radiator, or just the pulley ratio. Everything taken together.
The "maximum cooling" cars were a .95:1 with an HD water pump. The AC cars were 1.2:1 to 1.4:1 depending on the engine, but they had standard water pumps. Think about what the AC cars have- a big condenser sitting out in front of the radiator. It lowers airflow through the radiator. At speed it's not as big a deal, there's a large volume of air. But at idle or slow speeds when you're depending on the fan, that restriction is a much bigger deal. So, the pulleys are overdriven, the fan turns faster and moves more air, and the water pump is "downgraded" to standard to keep the amount of water moving close to the same.
Just saying overdrive the pulleys isn't a magic bullet. The OP already has a HD water pump. 1:1 on the ratio is more likely what he needs, but he needs to increase the air flow.
I said that. If the fan is within an inch and a half or so, you don’t need it. Some of the aftermarket shrouds are straight junk. The OE’s used them because the fan was too far from the radiator to be effective at idle and low speed.
I can’t remember where I read it, may have been an ASE paper or maybe it was some engineering testing, but a friend let me read this paper and it was about how a fan shroud can cause the air to stack up at the radiator when the road speed was high enough, the RPM was high enough and the shape of the shroud.
IIRC a short, blunt shroud was about useless. It would stack air up very quickly. It never really changed the coolant temp but, it did act like a giant air dam because the air can’t get past the fan and the shroud.
That’s why I get the fan as close to the radiator as I can and skip the shroud. The only real issue without one is getting caught in the fan. I need to fabricate something around the top of the fan for that, but no shroud for me if I can avoid it.
You have to be careful here. Some of what you're saying is true, but then you're taking that and making assumptions that aren't.
Yes, a poorly designed shroud that's too close to the radiator can cause issues when the car is at speed. That's why you see some of the aftermarket shrouds with doors and flaps and things that open up. They're trying to compensate for a poor design, or one that they've compromised due to space limitations.
BUT, fans are more efficient with a shroud. Putting the fan closer to the radiator doesn't fix the problem. When the car isn't moving, the fan is pulling air. What the shroud does is two-fold- it sets the area that the air is being pulled from. So, all the air that the fan is pulling goes across the radiator core. If the fan is too close to the radiator, it will not pull air evenly across the entire core, and you lose efficiency. The other thing is that the fan will bleed air around the sides of the fan, some air goes around the fan, some air is churned up by the fan but not pulled across the core or directly cleanly away from the core. That's what the lip on the shroud does. It ensures that all the air is pulled across the core, it keeps air from bleeding out around the fan blades, and it directs the air away from the radiator and fan. Setting the depth of the fan in the shroud also plays a big part, you need the lip on the shroud in the right spot to keep air from bleeding out and improve efficiency.
So just putting the fan close to the radiator doesn't do all of that. You still lose efficiency. The distance of the fan from the radiator from the factory wasn't too far, it was to maximize the efficiency of the fan. Sure, some other models have really deep shrouds because the engine compartment was so large (like C-bodies), but A-bodies don't have that issue.
Aerodynamics and air flow are complicated subjects, and you can't just oversimplify like that and get good information. Yes, there are badly designed shrouds that can hurt your cause. But a well designed shroud will absolutely improve efficiency. The OP's car could easily make use of an OE shroud, and I bet he'd improve his cooling efficiency 10-20% just doing that.
Funny how I never had a cooling issue with these cars back in the 60's, 70's, but that was original cars, not pieced together, bored out, parts missing, corroded engines, etc!! I have yet to build an old Mopar and address all the issues (post $5) plus a few more and not have a car run at the temp. it should. Yes some engine combos will run otter than others.
Using the OE and "back in the day" arguments for the original radiators has pitfalls too. Most of us have doubled the amount of horsepower our engines are putting out, which increases the amount of heat generated by more than two fold. The factory cooling system was designed for a lot less horsepower, but was also designed to be pretty robust, so it works for a lot more horsepower than was originally intended. But some of that is how these cars are used now too, you can get away with some things on a "weekend car" that would bite you on a daily driver.
