Why are these Broncos so hard to cool? I know a lot has to do with certain mismatched parts, mods, etc. But my question is why doesn't other Ford vehicles with SBF motor have these problems.
Shame to miss out on some fun because of a problem like this clarrance. But I can also understand the frustration.
I've been convinced for a long time that radiator size and capacity is not really the main, or certainly
only underlying issue with Bronco cooling. At least where a stock or very mildly modified EB is concerned anyway.
Only because I'm pretty confident that the Ford designers did take the usual things into consideration when they originally put these rigs to paper.
Though from what I remember, I'm pretty sure that the Ford truck radiators appeared to me to be smaller than the comparable GM and Dodge truck radiators of the day.
And while I heard a
LOT of complaints about running hot from Ford full-size truck owners from the early to late seventies, I never heard of any that from any of the other brand's owners that I knew. Pretty much ever.
So maybe there's something underlying all this whole "size matters" thing after all?
Not the cars so much, but the truck radiators always looked smaller. Could just be the footprint/shape though, as I've never compared fluid capacities before. Hmm, maybe that'd be an interesting thing to find out.
You can't really compare any truck to any car of this vintage either, I don't believe. Aerodynamics and weight and engine tune and gearing and tire size/rolling resistance alone, when new and then after modifications, can all play a huge role in how air flows over the fins and how many BTU's are generated by an engine for a given use. BTU's, Calories, Watts, whatever unit of measure they use for heat generation from an internal combustion engine an the cooling system's ability to transfer that to the air, are all I'm sure a bit different for the cars. The theories are the same, but the actual realities can be very different.
If nothing else, I think that "most" cars had more thought put into the aerodynamic flow stuff than "most" trucks did at the time. So they might just throw a bigger heavier radiator at a truck than a car, but that was not always enough.
The trucks are heavier, have traditionally lower powered engines of the same size (more torque at lower rpms usually, but still less overall HP) carrying that greater weight, use different gear ratio equivalents, have much poorer aerodynamic shapes to push through the air, and so have a HUGE difference in how efficiently air flows over, under and around the radiators.
The high-pressure areas under the front end alone are hugely different. Add a foot or two of height change to the equation, not only with lifting the truck, but with the larger tires and that high-pressure area increases it's effect massively.
And since those same larger tires are also harder to get rolling and keep rolling, the engines are working harder even without adding anything else to the mix. Keep the same gear ratios too then, and the load on the engine has increased by quite a bit. Enough perhaps, to overcome any oversizing of the cooling system that might have been built into it almost 50 years ago.
So while none of that may have any bearing on why yours runs hot, they're all things that can add up to overcome any extra capacity for heat dissipation that the factory had ever imagined they'd need, and had built in to the design of the truck.
Make one undercalculation then, in capacity or presumed ability to flow air over the fins instead of around them, and it won't take much to push it over the edge.
Change the engines too then, whether just in tuning or in especially in an overbore, which is acknowledged as a quick way to run hotter in a Windsor-family engine, and that's just one more nail in the coffin.
For comparison to what I just rambled on about, I don't remember
ever hearing of a stock Bronco that ran hot around here back in the day. From the first one a friend of ours had in '66 at Lake Isabella, to the brand-new '77 that a neighbor brought home in San Jose, to all of my buddy's rigs. None of them ever had a complaint about it being even a tiny bit hot on the hottest days or worst commutes. The first time I remember a slightly hotter running Bronco, was a friend's '72 AFTER he'd rebuilt the engine and added a 4bbl carb and the infamous "RV" cam and headers.
Darn thing always ran slightly hotter after that. Before that it was perfect.
When they were mostly stock and the only changes were to cut the fenders and put on "massive" 32" tires, overheating just wasn't an issue around here. Nor was it with customers when I started working in the 4wd industry. No internet to compare notes back then of course, but between magazines and word of mouth, the word about heat was just not an issue.
I remember maybe a couple of people talking a bit about it in Southern CA, so it wasn't completely unheard of. But it was never much of a deal either.
We never ran over temperature when doing the Rubicon in the height of the summer, or daily-driving in the city, or on any trip anywhere.
But that was stock...
Paul