'Stude,

You should run at the very minimum a 180 degree t'stat. Since the truck only heats up at lower speed and idle, airflow is most likely your problem. Keep in mind that there isn't a fan made that can duplicate the airflow caused by movement of the vehicle. If the truck cools right back down as speed increases, the temperature you are seeing is really not that high.

There have been several threads and posts concerning coolant actually flowing through the radiator TOO fast for proper heat rejection, I believe you can do a search. I won't try to get into a whizzing contest about this, but I do ascribe to this theory.

Personally and professionally, it has never been proven to me that an electric fan is a suitable substitute for the correct engine-driven fan and a proper shroud. Of course, opinions are like belly-buttons, everone has one...

Johnny

 

Stude,
Is the fan mounted flush to the radiator, and is it getting full current? They draw a lot of amps, and if the relay doesnt have a direct 12V supply it may not be sucking as much air as you think? Or if your alternator is too small maybe the same problem.

 

Thanks folks, for your comments.

To me it seems that the problem is the low air flow in the radiator. As this is the second engine I use in the same truck, with the same problem. But I don't how to increase the air flow. Until two weeks ago, I was using a mechanical fan (in water pump) plus an electrical fan in front of the radiator and even with both fans, the temperature goes up (210 oF) very fast in low speed or idle. I tryed to solve this, buying the 16" electric fan 3300 CFM, but it didn't work. Now I'm don't know what to try.

 

Hi 46yblock,

I realy did not check is the fan has the full current, but I'll do it. The alternator is 100 amp, and I thing is enought. According to the Fan supplier, the consumption is around 14 amp. But I need to check this issue. thanks for you hint.

 

Stude,

Sometimes, we overlook the obvious. Have you checked to make sure the electric fan is pulling air from the front of the truck, towards the engine? I have seen both electric and mechanical fans 'blowing' instead of 'sucking'...

Johnny

 

Stude,

Depending on the type of alternator & how it's wired, the fan may not be getting enough voltage. See the new thread about electronic ignitions, it has some information about alternators as well.

Another thing to look at, as far as your overheating problem, is that air has to be able to get OUT of the engine compartment as well. I've seen a couple of cases where all the fan CFM in the world wouldn't help because there was nowhere for the hot air to go. The owners had done all sorts of beautiful, trick, aluminum shrouds & panels.....looked great, but also blocked off all the airflow out.

46,

Did you have any luck with the thermostat yet? I saw your thread over on the other board, no dates for the posts, though, with the hacking. The FlowKooler thermostat I listed is actually a re-packaged Robertshaw...but I see Summit has them on backorder, & Jegs' site was down last night. Maybe FlowKooler has a website & dealer list.

 

Johnny,

I am with you on the coolant theory- I think it can form a "boundary layer", like air does, against the castings, & to an extent the radiator tubes, & creates something of an insulating layer under certain circumstances & speeds. Howard Stewart doesn't buy into it though, & he makes pretty damn good NASCAR water pumps. I guess I file it under "contributing factors". Most of my experience has been where the problem's obvious, though; bad radiator, too small radiator, clogged with debris radiator, clogged-fin radiator, overheated head radiator behind the steering wheel...

We don't normally have whizzin' contests over here, we leave that to the truck forums.

 

Homespun,
The Summit order is laying here filled out. Just need to get the m.o. I sure hope the Mr. Gasket brand of Robert Shaw type thermo isnt back ordered. For anyone interested it is part number MRG-4364, brass and copper. There is a large list of motors the part number fits. I think they included FEs, certain years of Chrysler 318's, Plymouth 340s, to list a few. But if you ask for a thermostat to fit a 1956 292, they will tell you it isnt available.
I looked at Stewart Product's thermo, and was going to order it direct. But the minimum shipping equaled the stat's cost of 12.95. Closest dealer was in Washington so called them to order it. They didnt want to mess with it and gave me the Mr. Gasket number.
What a hassle.

 

Homespun91,

The alternator issue I need to check, because I really don't know how much charge it supply. Regarding to hot air flow exit, I'm sure that ther is not a problem, as I have in the internal side of the fenders, some windows (holes).

Captradiator,

That was one of the first things I've checked. And the electric fan was blowing and the mechanical fan was sucking de air.
Another thing that I don't tryed yet, is to reduce the water pulley, to increase the water pump RPM, and than increase the water flow. BUt I don't know if this may help or make worse the situation ?! Because if you have more water flow, the water speed is higher and the time in the radiator is lower and problably the temperature is higher ?!

 

Stude, how hot is it in Brazil this time of year?

 

Hi 46yblock,
Around 95 to 104 oF. That's the point, I just have the temperature problem in the summer time. All other seasons, the engine stay cool. But in the summer, with very hot day's, the engine becames very hot too.

 

Going back to Johnny's first reply, with those outside temps you may be stuck with 210 when standing still. Or, could the new radiator have been plugged up with scale from an old motor? Too much paint on the radiator core?
You could get a machine shop to increase the center hole diameter of a car pump pulley and try it. It would reduce water flow a little, but it would just be trial and error. An option to increase radiator H2O flow would be the use of a thermostat talked about above.
If I'm wrong here someone please correct. A 35% solution of antifreeze should result in better heat exchange than the standard 50/50 solution, and a 25% better than a 35%.

 

Yeah, that's how I understand it, too.

Actually, we had good luck in roundy-round racing, using plain water and adding Red Line "Water Wetter" (breaks the surface tension & is actually even more effective than water by itself). It's not a bad idea to use block drains with water, though.

 

Yep, plain water is what is used in NASCAR, unless it's an early spring race in, say Virginia or North Carolina. Bear in mind, though, that these cars/trucks run about a 22 pound cap, since the water boils at a much lower temp than a coolant mixture. (For every pound of pressure, the boiling point is raised about two-and-a-half degrees.)

You have to rob Peter to pay Paul, due to the fact that the weaker mixture cools better, but not only boils over at a lower temp, BUT also does not give the proper protection for the different metals involved in the cooling system. Most late-model vehicles run, at the minimum, a sixteen pound cap, with some as high as twenty pounds. By doing this, in addition to the boil-over protection, smaller radiators can be used, thus saving weight and thereby improving fuel economy.

Finally, I'm in total agreement about whizzin' contests, they are totally non-productive. This is what I consider a serious, spirited, educational discussion. I just hope that I do not come across as a know-it-all, but rather someone who is sharing his forty-plus years experience in the radiator/cooling system business.

Johnny

 

Folks, once again I would like to thanks to everybody for your coments and technical explanations. I don't remenber if I said before or not, but I'm here in south of Brazil, in a very hot place (summer time). Well, As you problably know, here we do not have many options of spair parts, specially for the Y block 272,292. Normally when we need something, we import from USA. So, Johnny, what you exactly mean with "plain water" ? In your opinion is recomended to change my radiator cap from 13 to 16 pounds ?