Thread: Another radiator question.

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As I've mentioned, I'm going to mount the radiator on my '39 Dodge truck in the bed, and need some advice on mounting it. First some facts. The engine is a 394 Olds with some mild mods, running through a 4 speed hydro. The bed is open in the front (against the cab) and the metal tonneau cover is punched full of 244 louvers. I am also going to either louver or holesaw lots of holes in the tailgate. Point is, airflow should be no problem. Also, running the water through some piping that is about 1.5 inches in diameter all the way to the rear and back again should add some capacity and additional cooling.

I have lots of room in the bed, it is about 42 inches wide x 42 long x 18 high, so I can get a big radiator back there. I am thinking one of the 19 x 31 aluminum universal crossflow ones. I also have room for a 10 gallon tank and battery, with room left over.

Here is my dilema: I can mount the radiator one of two ways.........

1) Standing up like most radiator but back against the tailgate with one or two electric fans pushing air through the radiator and venting out through the holes I punch in the tailgate.

or,

2) Laying flat down on top of the rear kickup with the inlet and outlet pointing down with the hoses coming into the bottom. In this position the fan(s) would be on top, pulling the air up through the radiator and out through the louvered tonneau cover.

I actually prefer the second option as it would make mounting the gas tank easier, but my question is, will a radiator properly distribute and flow water if it is laid flat? Airflow would be just as good IMO, and I plan on building some sort of airdam under the car to scoop up air when underway. My opinion is that a radiator doesn't care how it is laid, it will still fill up with water and transfer heat just the same. I even think I have seen some exotic cars with radiators either laid flat or on a shallow incline.

Here is a picture (but not a good one) of the area I will be installing it in. Anyone have any thoughts on this???

Don

O.K. buddy, you asked for it It doesn't know or care, all it wants is the correct water flow threw it and some clean air going threw it. So how are you going to move all that water,stock water pump?
Ken

That is something I have to figure out too. I think the stock water pump moves a ton of water, but maybe I will have to add an electric booster pump in the middle to suppliment it. Not sure. I am going to add one of those in line water fills with a cap on it so I can put coolant in the radiator, I do know that.

What is your opinion on the flow Ken?

Don

I built a '29 Model A sedan delivery with a Hemi Ford (740 CU.IN.) and had to put two radiators in it. I used a electric pump made for a RV hot water tank. The rear radiator only had an inlet and outlet and a bleeder valve in it. If you do decide to do this it is really not that bad, just some more fabricating. Will you put a small radiator in the front or nothing?
Ken

No radiator in front, only this one in the back. I like the idea of the RV pump. What size hoses go to it? I'm wondering if I really need 1.5 or so hoses to the back or if something like 1 inch will flow enough.

A few years ago there was a T bucket at Turkey Run that had a big blown engine in it, and he had two radiators like you describe. The second one was up against the tailgate, which was cut out and screen put over the holes for cosmetics.

Don

Don,
I don't use thermostats, I just use washers in the thermostat housing. I just adjust the diameter of the hole in the washer to regulate the time the water is in the radiator. So if you go with that theory, you can use a 1" i.d. in your washer and a 1" id. in the radiator hose. If this doesn't make sense I will try again. You know about my writing
Ken

I just remembered, some marine engines use a "raw water pump" that is designed to suck water out of the body of water you are in and then the regular water pump becomes a circulating pump. If worst comes to worst I could mount one of these on the crank to boost the flow of water to the back.

Don

Originally Posted by Ken Thurm

Don,
I don't use thermostats, I just use washers in the thermostat housing. I just adjust the diameter of the hole in the washer to regulate the time the water is in the radiator. So if you go with that theory, you can use a 1" i.d. in your washer and a 1" id. in the radiator hose. If this doesn't make sense I will try again. You know about my writing
Ken

No, that makes perfect sense. I even thought of leaving the thermostat out altogether and using nothing that would impede the water flow.

Don

You can do that but if it doesn't stay in the radiator long enough to cool. Remember, the radiator takes the heat out of your water if it isn't restricted to stay long enough it won't cool properly. I would suggest you restrict it with something. Be sure your external pump is designed to move hot water.
Ken

a radiator that would normaly cool the engine your trying to cool would flow approx.26-32 gallons per minute.not sure if you would need an extra pump.I would install a good temp gauge and go from there .as far as the position of the radiator I dont think it would matter alot as stated in the earlier post.as long as it has air moving across the fins.

I agree with you guys, I think the long run alone will drop some heat and I can get the biggest radiator made back there. I might actually have the opposite problem, running too cool. That is a problem I will take though.

Glad to see you guys agree that laying it down won't cause the radiator to only partially fill up. My opinion is that the pressure will insure it being filled at all times. I like the vent idea Ken, to bleed off air. The radiator will be sort of as high as the top of the engine, so that is where I could bleed it off.

Don

I just found this thread. Here's my two cents... The radiator can be ALMOST flat, but needs just a little tilt (as little as 1/2 inch) so that air can rise to the highest point to be bled off (Obviously, your bleeder has to be at the highest point of the radiator). If it's completely flat, air bubbles can get trapped in various places. If there's air pockets in there, then the coolant isn't touching the metal. The heat is removed from the coolant by transferring to the metal and then being blown off into the ambient air, so air bubbles inside the system are your enemy.

Back in my stock car racing days we used to use the radiators out of Olds Cutlass Diesels because they had 4-row cores and we thought they were the best thing available. We used a restrictor washer instead of a thermostat. On a really hot night the car would run hot anyway, sometimes 230 degrees. Finally, one time when we had a few extra bucks, we bought a Howe aluminum radiator. We had to put a thermostat in it because we couldn't get it to run hot enough!

If you use a 19 x 31 Howe or Afco radiator, it should cool OK with the stock pump. Consider the Pontiac Fiero...

J. Robinson has it right on, you'll need to be able to purge the air out. So a slight tilt would allow that to happen. Shouldn't need a second pump though, the DeLoren had a V6 Volvo engine and the rad was up front. Coolant was moved through 1 1/2 inch aluminum tubing with rubber hose elbows, nothing but the engine pump was used. If I remember right, I think they ran two rads, neither one was real big. Long, narrow, and two core aluminum, they didn't have much height to work with, with the sloped wedge nose. I used a tilted rad on the airplane I built, with a petcock on the high end to purge the air. Inlet and outlet were at the same end of the rad, with a divider plate welded in between. The coolant travelled down one half of the rad, across the end tank and back up the other half to the outlet. The amount of air going through the rad, is going to make or break the attempt. I had a small 4 cylinder Chevette rad, but I also had a 6 ft fan up front to suppy the air. Sniper

Jim and Sniper........very good points. I was thinking of slightly tilting the radiator, but for space reasons. The bleeding of air thing makes perfect sense, and I will have a radiator shop add a bleeder to the top tank. Honda's have a bleeder on top of the engine, and after working on one if you don't open it until you get no air bubbles, it will overheat. (Don't ask how I know........ )

The 19 x 31 size is perfect and in fact I have 40 inches width back there to work with. With a 16 inch SPAL fan or maybe two 14 inchers I should have no problem cooling it. The bed cover is punched with 224 louvers and I plan on punching more holes in the tailgate too, so air should be able to move through well.

Sniper, you have given me an excellent idea. I was thinking steel tubing for the pipes going to the rear, but alumimum makes so much more sense. I bet I can pick up some 1.5 and 1.75 locally and it should also dissipate heat better than steel would. Thanks for mentioning that.

Don

If you have access to a dairy supply place, or a larger steel supplier, you could go stainless tube. I had short runs of aluminum on the plane, after a number of years, it did show some corrosion in small spots on the inside of the tube. Even with the antifreeze 50/50 mix. A bonus is, the exhaust shops can bend the stainless with no problems, less joints, less leaks. As a side note. Had one guy make the headers for a Vee Dub powered plane from stainless. Had them tig welded, looked nice when done. Just thinking the piping could fit up nice and tight to the vehicle with the proper bends, would look like they grew there! Sniper