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How to Insulate Your Exhaust System

How to Insulate Your Exhaust System

writer: Ted Olmsted, Tom Boyd
photographer: Tom Boyd

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Cooking camp breakfast on your rig scores big cool-factor points. We all love our manifold burritos, but too much heat is a bad thing. How many of us have modified our rigs and later realized that we created a different problem someplace else? In our case, we knew the route of the exhaust and the placement of the crossover Flowmaster muffler were going to generate a lot of heat on our '71 Bronco. When we installed the full belly skidplates and the interior panels above the exhaust we wound up with a convection oven; things got too hot too fast.

Different heat sources need different remedies. Exhaust tubing can be wrapped to keep heat in. Starters and other components can be wrapped to keep heat out. Thermal barriers with an air gap can be placed next to a heat source to deflect heat from sensitive areas, while still allowing the heat to dissipate.

We contacted Heatshield Products of Valley Center, California, for the lowdown on staying cool and keeping runaway temperatures under control. We used an assortment of its products and put them everywhere we thought they would make a difference.

The items we selected on our test rig really made a difference. We were able to reduce cabin heat from extreme hell down to nearly pleasant. With our Raytech heat gun we measured everything and found that even the area over the muffler was cut from well over 500 degrees F to 102 degrees F. We lowered our floorboard temps by over 100 degrees F. The area under the seats went from 150 to 100 degrees F. Numbers are great, but the real payoff came when we got back on the trail and didn't melt the fat off our ham hocks. Applications for this space-age technology are unlimited, and we turned our rig into a cool fool.


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On our '71 Bronco we've got fuel and electrical components as well as vital shifting cables sharing oven space with the exhaust and drivetrain. Header wrap was installed first to try and keep the heat contained until it got farther along in the exhaust system. High-horsepower engines produce more heat than a stock unit, and our built 302 is no exception.
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Header wrap stays in place with these cool-looking Thermal-Ties. The wrap can handle a continuous 1,000 degrees F so you don't have to feel the heat. The exhaust heat stays inside the exhaust system until it gets closer to the tailpipe, keeping components that are close to the exhaust much cooler.
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The muffler needed a heat barrier with an air-gap above it, so we used pop rivets to hold this Reflect-a-Shield to a rigid panel. This material can reflect temperatures of 2,000 degrees F continuously. This is just the ticket for catalytic converters and other big heat-producing components. We installed ours to reflect heat down and away from the passenger compartment.
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These 3-foot lengths of aluminized cloth can be pulled over the fuel lines and wiring harness like a long protective sock. Cooler fuel has less chance of boiling and causing vaporlock. Fuel pump cavitation due to boiling fuel is a leading cause of pump death. We also cut pieces of Reflect-A-Cloth to wrap individual components as needed. The fuel pump and bulky wires were wrapped in place with multiple layers of the stuff. Electrical components are more efficient at lower temps, thereby drawing fewer amps from the electrical system. This rig was later romped on for a week in the desert at temperatures far exceeding manufacturer's specifications. We finally burned up a fuel pump relay under the hood, but everything that was protected is alive and well.
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Let's face it, every hole in the firewall turns into a blowtorch on a hot day. Duct tape withers and blows away, but this adhesive-backed Reflect-A-Tape makes a quick yet lasting barrier to engine heat. It can also be wrapped around shifter cables and other hard-to-reach areas. We amazed a buddy with a Jeep by how fast we could make his rig comfy. Purists will be delighted to know that the tape can be painted to make it look factory cool like this olive-drab '47 Willys.
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We finished off our heat problems with this kill shot. A 40-inch-wide section of Reflect-A-Cloth is available in any length you want. We cut ours to fit the transmission hump and had a canvas shop sew the pieces together. We mechanically fastened ours with rivets, but a high-temperature contact adhesive will also work provided the surfaces are clean. We positioned this barrier under the complete cabin for a huge improvement in the cool factor.
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We used our cool Raytek Mini Temp infrared heat gun to measure the temperatures before and after each upgrade. The gun is inexpensive, easy to use, and very accurate and has multiple uses for other projects in the works. We found temperature drops of almost 400 degrees F in the muffler area, although we didn't need the Raytech to figure that out.

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