DIY Heatcore: Inexpensive and Great Performance

With the heat levels produced by most modern processors, watercooling is gaining more and more attention in the mainstream cooling gear market. Of course, the appeal of more efficient cooling that can be had through watercooling, as opposed to traditional heatsink and fan cooling solutions, has drawn overclockers to it since its inception.

The reasons for turning to liquid cooling methods are fairly straightforward – overclocking often requires higher voltage settings for the CPU, as well as other components, to gain stability at higher clock speeds. The increased voltages result in higher temperatures and the need for more efficient cooling. Watercooling can deal with the heat from the higher voltages much more effectively than a heatsink and fan and it can often do so with less noise than air cooling solutions.

The usual components found in a watercooling loop are a waterblock for the processor, a water pump, a reservoir or t-line, and a heat exchanger. Traditionally, heat exchangers were often items that were originally intended for some other purpose, such as automobile transmission coolers, with modified fittings so they could be plugged into a watercooling loop.

More recently, companies have began developing radiators specifically for use in watercooling systems but most of these have the drawback of being somewhat expensive. While watercooling components have gotten less expensive as more companies have entered the watercooling market, a good watercooling system can still put a nice dent in your bank account. Obviously, any alternative components that will provide equal, if not better performance, while costing substantially less than commercial H2O parts are worth investigating even if they require some do-it-yourself garage time to get them ready for use in a cooling loop.

One such viable alterative that is readily available and easily modified is a heatercore. While there are many different models that can be modified to work in a watercooling system, one that has gained quite a following is the Chevrolet Chevette heatercore. More specifically, the heatercore for the 1986 Chevette, Fedco part number 2-161 or GDI part number 399069, which is approximately 6-1/8″ x 6-3/8″ x 2″. The factory tubes are 3/4″ and 5/8″ which require some modification to work with 1/2″ ID tubing used in a watercooling system but this modification is not that complicated and well worth it considering that most auto parts stores have this heatercore for around $22. Additionally, the tools needed for the modifications are fairly inexpensive and they are likely ones that most already have on hand.

Modding a Chevette Core
The list of supplies, parts and tools needed to modify the Chevette core will depend on the particular method used as well as the skill of the person doing the modification. To make this as straight forward as possible, I’ll break it down into two different methods which require slightly different parts and tools. The first method is an epoxy or cold weld method where the second method is a soldering method that requires a few more tools

Tools and Parts	Copper Fittings

The information contained in this site is for guidance only. The application of this tutorial can differ extensively based on the particular items involved. The information on this site is provided with the understanding that the author(s) and publisher(s) are cannot be held legally responsible for any injury or death that may result from this or any other article at OCmodshop. With this being said be sure to understand what you are doing before you attempt what is being shown. If you have any questions about any aspect of the article please contact the author or another experienced individual before proceeding.

Parts, Tools and Supplies

The Epoxy or Cold Weld Method:

• 1986 Chevrolet Chevette heatercore
• JB Weld or two part high strength epoxy
• 220 grit 3M wet/dry sandpaper
• A hacksaw, Dremel or copper tubing cutter
• Two 1/2″ pipe to 1/2″ female NPT thread fittings or two 1/2″ pipe to 3/8″ NPT female fittings (available at most hardware stores)
• Two 1/2″ brass barb x 1/2″ male NPT threaded fittings or two 1/2″ brass barb x 3/8″ male NPT threaded fittings
• A short piece of 1/2″ ID copper pipe (this can be cut from one of the original tubes on the heater core)
• Teflon tape or pipe joint compound

Chevette Heatercore Packaging

The Soldering/Sweating Method:

• 1986 Chevrolet Chevette heatercore
• A small propane torch (like those found in plumber’s kits)
• Flux and solder (can be found in a plumber’s kit with the torch for around $15) or acid core solder (auto parts store ~$3)
• 220grit 3M wet/dry sandpaper
• A hacksaw, Dremel or copper tubing cutter
• 3M Wet/Dry Sandpaper (600 grit) or a small needle file
• Two 1/2″ pipe to 1/2″ female NPT thread fittings or two 1/2″ pipe to 3/8″ NPT female fittings (available at most hardware stores)
• Two 1/2″ brass barb x 1/2″ male NPT threaded fittings or two 1/2″ brass barb x 3/8″ male NPT threaded fittings
• A short piece of 1/2″ ID copper pipe (this can be cut from one of the original tubes on the heater core)
• Teflon tape or pipe joint compound

Part and Supplies for the Heatercore once it is finished:

• Primer, spray paint and clear coat if appearance is important. Duplicolor is a good choice. (optional)
• A premade shroud like the Coolingworks Coolshroud
• A good 120mm fan such as a 120mm x 38mm Panaflo or 120mm x 38mm SanAce

Okay…so heatercores get no points for glamorous packaging but we are chasing down high performance for dirt cheap pricing so no harsh comments on the white box. Moving on to the contents of the unbelievably ugly box.

As can be seen in the above picture, heatercores are pretty rough straight out of the box. Additionally, heatercores can have defective seams right out of the box so before modifying anything on the heatercore, leak testing is a very good idea. The best way to test for leaks is to fill up a container (or the kitchen sink if the wife/girlfriend is not looking) and lay the heatercore in the water. Once it is submerged, plug one of the tubes and blow air through the other. If any air bubbles start streaming from any of the seams on the core, take it back and get a new one. Always test them before doing any modifications.

Regardless of which method is used to attach the new fittings, the initial preparation steps are the same. The first step (after leak testing) is to cut down the factory copper tubes so that the new adaptors or fittings can be joined to the factory tubes which are attached to the tanks on the heatercore.

 

The factory tubes can be cut to the right length with a hacksaw, a Dremel with a high speed cutoff wheel or a copper tubing cutter. The a mini tubing cutter is likely the easiest method as the mini cutter will take care of the task in only a few seconds with very little effort. To be on the safe side, it is usually a good idea to leave the tubes a little longer than what it might appear to be required. If the tubes end up being a little too long, it is much easier to trim them down than to replace the tubing to get the right spacing after cutting them too short.

Tube and Fitting Prepared for Cold Weld
Once both tubes are trimmed, the tubes should be roughed up a little with 220 grit sandpaper. Roughing up the tubes will get rid of any surface oxidation or other substances that might keep the epoxy or solder from adhering well to the copper and it will give the surface of the copper a texture that the epoxy or solder can grab on to. Once it is roughened, the copper should be wiped down with a paper towel and a little alcohol to get rid of any leftover copper dust.

Cold Weld/Epoxy Method
In order to get clearer images of this method, I used a spare section of copper pipe with a copper fitting and then added images of fittings attached to the heatercore with JB Weld. As stated above, the copper tube should be roughed up a little and then cleaned with alcohol and a paper towel. The inside of the copper fitting that will be attached to the tube should also be roughened a little and cleaned. Then, a small amount of 2 part epoxy/JB Weld should be mixed together according to the instructions for the particular type of adhesive.

 

Fitting Attached to Copper Tube
A 1-2mm thick layer of the adhesive should be spread around the outside of the inch of the copper tube and to the inside of the copper fitting. Immediately after applying the layer of adhesive, the fitting should be slipped over the copper tube. A bead of adhesive will likely form around the end of the fitting as it is pushed into place. The adhesive bead can be smoothed around the edge of the fitting with a slightly dampened finger tip so that it produces a smooth transition between the fitting and the tube.

Coating with JB Weld
After both fittings are attached to the factory tubes with the adhesive, they should be allowed cure according to the adhesive manufacturer’s instructions. With JB Weld, I usually let the heatercore set for about four to five hours before moving it and at least overnight before testing it in a cooling loop to check for leaks. After the fittings have cured, an extra layer of JB Weld can be added over the fitting and tube to provide a little extra strength. If the point where the copper tube meets the tank is unusually rough or if the tank has minor dents or ridges, a coat of JB Weld can be spread from the fitting back over the copper tube and the tank to provide a bit of filler that can be sanded smooth. This is strictly for looks but it can produce a nice flat surface to prime and paint if desired.

The solder/sweat method is a little more advanced than the cold weld method but it can be done really quickly and there is no curing time to slow down the process. Before covering this, a few preliminary notes are required:

1). Even though this method uses only a propane torch (which is not that hot by torch standards) it will produce enough heat as to where the flame or the copper heated with it can cause an extremely serious burn.
2). The heat from the torch will spread through copper amazingly fast – never hold any piece of copper that is being heated with bare hands or fingers or you will have first-hand knowledge of the burn previously mentioned.
3). Copper can retain heat for a very long time. Even after it might appear to be cooled down, it can still be more than hot enough to sear bare skin.

In order to add the fittings this way, the copper tubes and the fittings should be prepared in the same way as with the cold weld method (i.e. roughened and cleaned). Once the fittings and tubes are prepared, the core should be secured so that it will not be able to move or fall during the soldering. If you have one, a bench vise is a good way to keep the heatercore in place during this process but make sure to either pad the jaws of the vise or use only enough pressure to hold the heatercore in place. Over tightening a vise onto a heater will lead to nothing but trouble as it will damage the fins or the seams.

After the heatercore is in a fixed and stable position, the inside of the copper fitting and the outside of the tubing should be lightly coated with flux. If acid core solder is used, the flux layer is not necessary.

Sweating a Copper Joint
Next, the inside of the copper fitting should be pre-tinned. To tin the fitting, it should be held with a pair of pliers and heated with the torch to the point that solder with easily melt when touched to the inside wall of the fitting. Do not use the flame’s heat to melt the solder – get the metal hot enough to melt the solder when the flame is not touching it.

A thin layer of solder should be added around the smooth, inner wall of the fitting where it will meet the surface of the copper tubing. Be sure not to get any of the solder in the threads of the fitting as it will likely make properly tightening the brass barb into the fitting very difficult, if not impossible, later on.

The outside of the copper tube on the heatercore can also be tinned before attaching the fitting to insure a really solid and leak-free joint but this can also be achieved in another way that I will cover shortly.

To add the tinned fitting onto the smaller diameter copper tube, the fitting should be held with a pair of pliers near the tube and both the copper tube and the fitting should be heated with the torch until the solder inside the fitting and the solder on the tube melts. Once the solder is liquid, the fitting can be slid into place onto the tube and allowed to cool.

To make certain that the joint is solid and 100% leak-free, an additional technique known as sweating can be used. While it is most effective when the inside of the fitting and the outer section of the tubes are pre-coated with a layer of flux, it can be done with acid-core solder as well.

To sweat the joint, hold the fitting in place on the tube with pliers at a point as far from the joint as possible. Then use the torch to heat the fitting and pipe. Once it is hot enough to melt the solder, touch the end of the solder to the seam of the joint. The solder should flow freely and disappear into the joint. If it does not, heat the joint a little more until it does. Then, wipe the joint with a wet towel to clean and set the joint.

For the larger tube, the fitting normally has to be slipped inside of it. If it is overly loose, the copper tubing can be lightly crimped onto the fitting and then solder can be used to seal the seam and lock the fitting into place. While working on either tube with the torch, keep a close eye on the solder joint that holds the copper tube into the tank. Most of the time, fittings can be added onto the tubes without harming the tank-to-tube solder joint but occasionally it will melt. If it does just touch the point where the tube meets the tank with the solder and it should pull enough solder back into the joint to reseal it.

Although the below image is slightly blurred, the solder can be seen touching the edge of the joint right behind the fitting. Sorry for the picture quality but torching, sweating and attempted digital camera operation produces more of a circus act than a precise operation…Look! It’s Jo-Jo, the amazing torch-wielding, pipe-sweating, picture-taking, unicycle-riding bear! Never mind.

Once the soldering job is completed, give the heatercore enough time to cool down to room temperature before moving it. Moving the heatercore around while the solder is still hot can weaken or crack the solder joint. The worst-case scenario is likely a hairline crack in the solder as it might not leak today, tomorrow or even next week, but at some point in the future it will definitely leak.

Once the heatercore has cooled, it can be cleaned up in the sink with an SOS pad or some soapy water and a brass or stainless steel brush to get rid of any remaining flux or other grime. While it is in the sink, give it another leak test to make certain that none of the seams or joints became unsound during the soldering process. Since the heatercore will be nice and clean after the SOS/brush bath, it would be a good time to add a coat or two of primer and paint to make it look as good as it will perform. :)

Once the new fittings are attached and the heatercore has had a bath and another leak test, it should be ready for a nice paintjob. I normally add a couple of primer coats, a couple of color coats and then a couple of clear coats to greatly improve a heatercore’s appearance. If given the option, Duplicolor primer, paint and clear coat is what I use if it is available in the color I need. Getting a primer, a color coat and a clear coat from the same manufacturer is a fairly simple method for making sure you will not have incompatibility issues between the finish coats and Duplicolor paints are easy enough to find.

Before beginning the painting process, attaching the brass barbs to the core is a good idea. Attaching the barbs before painting keeps paint off the threads of the fittings and out of the inside of the heatercore.

Once the brass barbs are screwed into place, mask them off and make sure the ends of the barbs have a layer of tape over them to keep the paint on the outside of the heatercore. After masking everything, a couple of thin layers of primer should be sprayed onto the heatercore.

Do not spray paint or primer directly into the fins of the core as this can hinder its cooling performance. Instead, lightly dust the top edges of the fins from a fairly low angle while the sides of the heatercore are being coated. By just dusting the tops of the fins, the paint should go no deeper than about 1/8″ and it will not hurt the heatercore’s cooling abilities.

As can be seen in the picture, the heatercore was elevated off the bench a few inches which really helps get paint in the ridges on the sides of the heatercore. I discovered that a 4″ wide Tupperware type bowl that is about 3″ tall makes a very nice platform to set the heatercore on while painting it. Once again, make sure the significant other is elsewhere when you sneak into the kitchen cabinets and abscond with the ill-gotten Tupperware booty for your heatercore project.

After letting the primer dry per can instructions, two or three color coats can be added in the same manner. Always spray thin coats and let each coat dry before adding another coat to prevent paint drips, runs or nasty finish sagging. Once the color is nice and rich, add a couple of clear coats to bring up the shine and add some depth to the finish.

After letting the final finish coats dry overnight, carefully remove the masking tape and then remove the brass barbed fittings. Either wrap some Teflon tape around the threads on the brass fittings or add some of the pipe joint compound to the threads, screw them back into the fittings and tighten them down securely. The entire painting process is fairly simple, takes only a little bit of time and greatly improves the heatercore’s visual appeal.

To really get the most out of a heat exchanger, a fan shroud is required. Of course, a standard 120mm fan can be bolted directly onto the Chevette heatercore but the same heatercore with a good shroud will gain a performance boost of 35-40% which is well worth the cost of the shroud. While there are numerous ways to construct a shroud for a heatercore like the ’86 Chevette core, the easiest and most cost effective route is to buy one pre-made as there are several shrouds for this heatercore that are very inexpensive. An example of a good commercial shroud for the Chevette core is the Coolingworks Coolshroud. Check out the Coolshroud

Conclusion
While heatercores may require some modifications before being hooked into a watercooling loop and they are by no means beautiful right out of the box, a little time and effort can turn them into very effective and nice looking heat exchangers. Even after adding in the cost of the necessary parts or supplies needed to give a heatercore a solid transformation, they are still much less expensive than almost any other option and they will perform just as well if not better while still leaving extra money in your pocket.