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I am swapping a GM 8.1l engine into the honcho and I am planning to run a rear radiator in an effort to keep it cool.

What is the best material to use for the coolant lines that is reasonable in cost? I'm seeing on pirate that everyone is using anything from DOM, to aluminum, to EMT, to pipe and even rubber hose.

Thoughts? Whatever I use, must be very reliable...

In my younger days I ran around with Rod Hall's son Chad. I got to see quite a few of his dad's SCORE/BAJA pickups being built in their shop. Rod used 1-1/2" rigid copper plumbing pipe and sweat fittings for the rear radiator and it seemed to work great. The connection to the engine and rad were rubber hose which prevented electrolysis stripping of the copper by the cast iron engine block. This nice thing about copper pipe is you only need a torch, flux and solder to repair a leak out on the trail as opposed to trying to plug weld steel or plug aluminum or rubber.
I've seen 3/4" rolled soft copper tubing employed in the under seat school bus heaters back in the day. The tubing ran along the underside of the floor and was secured by rubber coated U-clamps.

well I don't carry a torch on the trail. But I do carry gorilla tape and at least one gallon of antifreeze. Guess if I went this route, I'd have to carry a torch and stuff on the long trips to Moab, dunes, Ouray, etc.

I started carrying a MAP gas torch after struggling to remove the tapered axle nut on a CJ-7 that had sheared the keyway while up on the Rubicon.
I think if I was going to do the rear rad setup, I'd use the heavy rubber hose used on Class A trucks which would likely outlast the rig.

Most buggies and baja racers and such run the coolant through the cage tubing.

I would not use rubber for the full length. Make the main length out of rigid tubing (material of your choice). Steel would be my guess, then run shorter rubber hoses between the rad and rigid tubing.

Tatsadasayago wrote: The connection to the engine and rad were rubber hose which prevented electrolysis stripping of the copper by the cast iron engine block.

I think someone was overthinking this. You'd want that connection to have some give for vibration and the frame flexing. Same at the radiator. At least that's why I'd use the hose.

Also, iron is sacrificial to copper. It's the one that would corrode.

You're quite right, I had it backward.

Rear rad only? If you ran dual rads I would use 1" copper tube and have shut offs in case one or the other sprung a leak. Especially desert driving. We packed 5 gallons of drinking water (and 3 days food) so that if we were stuck in nowheresville, we'd be fine and a major leak could be fed to get us back to the highway. I thought about filling the front bumper with backup mixed radiator fluid. Heck, I even considered plumbing the tube front bumper to the rad for extra cooling.

Copper would be a dual-edged sword; a nice long run to the back would help dissipate a good deal of heat in addition to the rads, however it's going to get pretty warm as well so you'd want to tuck it up somewhere.


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I think I'm gonna end up running 1 3/4" roll cage tube for the water lines. Only thrbrear radiator as I'm kinda curious how that works and I would like to move as much weight as possible to the rear.

The main problem with copper over steel is that copper work hardens, and steel does not. So if there is any flex in the copper lines, they will crack eventually. If you put enough flex couplings in the run, I would not expect this to be a problem. The main advantage is you can get dozens of different types and sizes of copper pipe and fittings, and they are easy to solder together to get the shape you want.

It's think the premium solution would thin-walled steel or stainless tubing. TIG weld it together, and join it with short lengths of flexible rubber tubing.