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Old 09-30-2010, 10:10 PM
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radiator in the back of my hot rod truck

Howdy! I want to put a radiator in the back of my hot rod truck.
Any how to stuff out there or pics would be cool.

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Old 10-01-2010, 05:37 AM
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Putting a radiator in an area that's out of the frontal airflow does create some problems. It can and has been done but so much depends on how much HP you plan to make with the motor. The more HP, the much more heat that has to be cooled. Also the lines needed to be routed from the motor to the radiator should be 1.5" to the rad, and 1.75" the return. The best bet is to get an aluminum radiator with 2 rows of 1.5" tube inside. That will give you max flow capabilities. Also needed are no less then twin fans with a shroud so you can pull max air thru the radiator. If possible as well , have some sort of duct work going to the radiator to help with outside airflow.
This is a job to design but it can be done but it can also be a nitemare.
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Old 10-01-2010, 07:11 AM
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Sunsetdart is on the money. Rear mount radiators are possible but they require some thought and design. Below are a couple shots of the rear mount in my roadster. And starting here in my journal you can see more pics and details on the fabrication and design.

That being said, after tinkering with this system since the time it was built (2005), I just last week tore it all out and I'm replacing it with a front mount aluminum radiator. The system was quirky from the get-go, but the major problem I had was the result of too many angles in the hoses and piping.

I don't recall the exact number at the moment, but every time you have a right angle in your coolant line, it reduces flow by 40%-60%. And to get your coolant from a front mounted engine to a rear mounted radiator is bound to require a whole lot of sharp angles and turns in your lines. So no matter how large a radiator you install, you end up with very poor coolant flow and a multitude of potential overheating problems.

Let me also second the comment about air flow. Not only do you need a high efficiency fan, you'll probably also need to create some sort of ducting or air dam to get the required amount of cool air flow up and through your coils.

Then you also have the problem with getting the heat AWAY. If you are mounting in the bed of a truck, as you are doing, you'll probably have no problem. But if you are mounting in the trunk area of a car, as I did, you have to contend with a huge amount of heat which even in a roadster was a problem in the cockpit area.

Don't get me wrong, it can be done. But if at all possible, I would highly recommend an exposed front mount.

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Old 10-01-2010, 07:39 AM
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A guy here did it on a rat rod.. He had a box tubing frame front to back,, And ran the water through the frame rails.. Had the rad in the back.. I didn't get to talk to him.. But I know he drives this thing all over...He has a lot of very good Ideas on this truck..ran the alt. off the rear end.. The list goes on and on on his truck.. I will try and get some pictures when I see it again.. He was at the coast one year, and I can say this ''everyone'' was around his truck pointing at something...I don't know If I would want the water running through the frame.. But I would like to know how much water it took to fill it up..
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Old 10-02-2010, 02:29 PM

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I am building a Corvair Rampside pickup that had an air cooled motor behind the trans axle. I will be placing a mild motor in the bed and coupling with a Corvette rear end/suspension. I know of another truck that has done this and he made a big duct that scooped air from under the front bumper and dumped through a closed shroud into the radiator that was located conventionally in front of the motor. The duct work and radiator was very close to the rear of the cab. He used a puller electric fan for cooling in traffic. The truck was fine up to about 55 mph but above that, the air flow over the cab created about as much pressure as the ram air coming in and it would start over heating. He solved this problem by removing the electric fan and installed a viscous mechanical fan. I plan to install my radiator behind the rear end in the old engine compartment. The coolant tubes will require minimum bending and I may build some additional finned coolers under the truck. The radiator will be installed with about a 30* tilt (low in the front, higher in the rear and I will scoop air into a shroud and will run a puller fan on the back/under side. The air flow will have to do some bending to get through the finned passages, but the scoop/shroud will certainly help. I will be running a big oil cooler which will be a aid in keeping the oil temp down and the oil lubricity.

You can see some pics of the mentioned truck by doing a Google search of Ken Arnold Corvair.
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