My brother bought a custom 74 Bronco that has a built 91 302 in it. He is experiencing overheating when at idle, but as long as you can keep the truck moving, then it will run sort of cool, like about 190-200 with a 180 t-stat. When it is idling, it gets up to about 245, but if you rev the motor up to 1500 rpm, it starts to cool off. This truck has a custom aluminum radiator and such, and the fan has no clutch, it is bolted directly to the water pump. I am thinking his water flow is not sufficient at idle and the idea of having the wrong water pump on it came up. His truck has the serpentine belt, so the water pump should be reverse rotation. Without taking it apart, what I can see is that the timing cover has a boss on it for a mechanical fuel pump with a Ford Motorsport blocking plate installed.

Does the presence of the fuel pump boss automatically mean his cover and pump are standard rotation, and are therefore turning the wrong way? Since the timing cover and water pump are a matched set, is there any such a thing as a reverse rotation timing cover with the fuel pump boss?

I am trying to not tear this all apart if there's nothing wrong with it but right now I am thinking he's got the wrong pump for his serpentine belt setup.

 

The 79-85 Mustang HO motors used a reverse rotation pump on the std rotation timing cover. It apparently didn't work well as Ford redesigned the timing cover and pumps for the 86 motors that reversed the coolant port layout in the timing cover and that resulted in a more efficient coolant flow. The 86-93 pump does not fit the earlier timing cover, this pump (and timing cover) was also used on the 86-97 pickup and van 5.0 and 5.8. You may also have the head gaskets on backwards, look at the lower front corner of the block, if the gaskets are correctly placed, there will be a section of gasket sticking out, covering the exposed deck surface of the block. If this corner of the block deck is exposed, the gaskets are on backwards, allowing the coolant to "shortcut" it's way back up to the head and out the intake, this will result in a hotter running engine.

 

If the Bronco has the original coolant inlet/outlet radiator, that too will contribute to the overheating as the inlet is directly above the outlet allowing a majority of the hot coolant to bypass the other side of the radiator.

 

His Bronco has a Ron Davis aluminum radiator:

B.C. Broncos - 66-77 Early Bronco Engine Cooling Systems

 

Well you didn't answer the question. There are a half dozen different radiators listed there in that link. And just in glancing at the link posted, he's dead wrong about the stock waterpumps. Stock waterpumps are not all the same. They come in three flow ratings, just like aftermarket pumps do. You do not have to buy an expensive aftermarket pump to get a high volume unit. All you have to do is a little homework in picking to get a HV stock waterpump.

 

I apologize, I thought you said if it had the original radiator in place, which it does not.

So now I guess I don't know what you mean here - can you elaborate?

 

Sounds to me like insufficient air flow.

 

The early Bronco radiator has the inlet and outlet on the same side (passenger) of the radiator. This allows the coolant to drop straight down to the outlet, bypassing half of the radiator, in effect losing half the cooling capacity of the radiator.

 

Is the fan shroud installed? Typical indication of not running one.

 

That's what my brother thought, but we got it up to 240 at idle and then put 2 shop fans in front of the Bronco and it does not help.

OK, I see, so no, the radiator has the inlet and outlet on opposite sides.

Yes, it has a Ron Davis aluminum shroud that matches the Ron Davis radiator.

 

Check the head gaskets to see if they're on backwards.

 

My brother checked (the Bronco is in Houston and I am in Austin, Texas) and he says he can see the head gasket sticking out the front so that means they are OK? He sent me a pic but I could not tell anything, it was too blurry.

 

Yea, the gaskets should be poking out the lower corners if they're on correctly. The waterpump could have a small impeller, that's designed for high rpm operation. This type pump will not move much coolant at lower rpms. Might be worth it to swap a high volume waterpump on it to see what it does then. You don't have to spend a fortune on an aftermarket pump though. Just a trip to the local parts house will get you one. Ask for a pump for a "Police & Taxi" , or "extra cooling with A/C" this should get you a high volume, large impeller pump. But then again, with that FEAD setup, you may be stuck with std volume selections. From your description, you've got a 79-85 Mustang FEAD setup, you may also might consider a swap in timing covers and waterpumps to the 86-97 style found on pickups and vans (also on the 86-93 Stangs)

 

That is what I have recommended him to do. Thanks for all your input.

 

Being an early Bronco, you might also consider the Explorer/Mountaineer setup or the similar setup used on the 89-93 T-Bird/Cougar or 94-95 Stang. These all have a shorter overall length, giving more room between the waterpump shaft and the radiator.