Does this sound like a radiator issue?

You might try an electrict fan

 

Von Rigg Fink, I didn't mean that your set-up won't work. Just that although you normally would be right it's not always so. I had a problem I chased for a while where on idle for over 20 min it was fine, but going down the road within a mile it was over 240. I finally found the cause, prior overheating had caused the tubes , aluminum radiator, to expand and close off all airflow because it squeezed the fins together. Another time a truck I had needed a new radiator. This was a BBC powered crew cab that carried a 10 1/2' camper and pulled a 4 horse trailer. After the new radiator was in we spent 2 months trying to figure why it was usually fine but come to a highway overp*** and the temp would start to climb. The shop that replaced it finally figured it out. The new radiator although 4 core the same as the original had almost 3000 fins less. The shop replaced at their cost and from then on it was trouble free.

 

go electric and you can put it where you need it...i know, this is where all the traditional guys go nuts..if you want to drive it you have to keep it cool.

 

Gotcha...
.just seems strange simular combination but different outcome.

I really hope when i put mine on the road this ugly problem doesnt rear its head..but than again changing a radiator is easy compaired to building the entire car from the ground up..so if that is the only issue i have to deal with..it will be an easy one

 

I would first try to fix the fan, even know the original sat low the swept area of the fan was all covering the core. With your fan being so low and the swept area being the bottom tank you will be pulling more air from below the radiator than through it. Some modern cars also have fans that sit low like this but they have a shroud that will only allow air to be pulled through the core.
Another issue is the gap between the top tank and the grille shell, you need to block that off as much as you can, air is lazy and will take the easiest rout, that being over the top of the radiator rather than through it.
If the Zip high rise water pump is too much you could try to run an electrical fan on the front of the radiator, this will limit the amount of air being drawn from the engine compartment. Just remember you want the fan to sweep the largest area of the radiator it possibly can.

Hope this helps a little, but some better pics would help.
Cheers,
Doc.

 

Seems to me that if you want to switch to an electric fan you should:

• Ditch the belt driven fan on the water pump pulley. It's redundant and wasting horsepower.
• Use the biggest electric fan that will fit.
• Make sure that it is thermostatically controlled.
• Put the electric fan on the back of the radiator if at all possible.
• Use a shroud.
• Center the fan on the radiator as well as you can given space limitations.
• If the radiator is much taller than it is wide consider using two smaller fans, one above the other and offset one to the left a little and the other to the right a little.

But I'd try to fix the radiator shrouding you have first. Like others have said you need to arrange it so that any air going through the grill HAS to go through the radiator, with no open paths above or below or on either side of it. The fan shroud needs to have the fan pulling air ONLY through the radiator and not through gaps at the top, bottom or sides.

And if that doesn't do it, is your radiator as big as it can be for that grill shell? If you have room for a larger radiator, find one that fills it up more even if you need to have one custom made to fit. (That probably won't be necessary, though.)

 

If it was mine, the first thing that I would do is take some poster board and make a pattern to block off the open area above the radiator so that all the air that enters the grill shell MUST to go through the radiator core. Then duplicate it in some sheet aluminum. You do not need a fan when the truck is underway if the radiator ducting is set up correctly. Yours is not. yet.

I detest electric fans so I'll keep my mouth shut on that option.

I'd double check the manifold vacuum to the vac advance. It will run cooler at idle that way. (not to mention that is how GM designed it)

Do the little things that are cheap first before you start to throw money at it trying to fix it.

 

What exactly do you mean by this? There were some very helpful suggestions given here. Put yours on the road, then you can make some factual statements.

 

Nothin' persnol..

just had asked a bunch of questions to help me help you sort it out back early in your thread.. mabe it slipped past ya..#10

my factual statements were only my experiance with using it in my build..and i do remember saying it wasnt on the road..
and still feel you have something else that is the cause of your cooling issue.

Have you looked into the condition of your pumps internals?
what pound cap?


its all good man, wasnt trying to bust on you, just trying to find out where to help