Exhaust System Insulation
Story & Photos By Jim Clark (The Hot Rod MD)
If you are building a highly polished showpiece, controlling heat radiation from the drivetrain and exhaust is not something that you will have to address. However, if you plan to drive it, shielding sensitive components like the brake system and wiring from damaging high temperatures is critical.
Some of the later model cars used for building a hot rod offer a reasonable amount of space under the vehicle for routing the exhaust. In many of the early model vehicles this space is very crowded though. In my “deuce“ highboy roadster this limited space was reduced even further due to the presence of the master cylinder being located below the floorboards and a big Turbo 400 transmission behind the Nailhead Buick, filling up the center of the big X-member center section of the frame.
Low ground clearance dictated that the exhaust needed to be routed through the frame and tucked up close to the floorboards. Once the system was installed I noticed that the mufflers and exhaust pipe were both very close to the master cylinder, brake lines on the left side and fuel lines on the right side.
Controlling Muffler Heat
To address the problem of heat radiating from the mufflers I found new Kevlar muffler covers from Thermo Tec. They wrap around the muffler and are held in place by stainless steel zip-tie straps. The material is not very bulky so it wraps nicely around the mufflers.
Kevlar Muffler Cover: Handles continuous temperatures up to 1100 deg F. Reduces radiant heat inside the vehicle. Dampens muffler noise and vibration. Includes stainless steel straps for installation.
The Kevlar material is very durable but is easy to cut with scissors after measuring it to fit. More than enough material is included for even the largest pair of mufflers that you might choose for your vehicle.
The wrap is held in place with these stainless steel zip-tie style straps. The end is passed through the opening and pulled tight. Once installed they can be repositioned to adjust their spacing.
This shot of the finished installation illustrates how little bulk that this wrap adds to the muffler while providing significant control of heat radiation.
Brake lines and wiring to the rear of the vehicle are routed along the left frame rail so heat from the muffler had to be controlled. The metal floorboard above was insulated on the topside but the close proximity of the muffler to the bottom side also needed to be addressed.
Controlling Exhaust Pipe Heat
Exhaust pipe from the engine on the left side had to be routed up through the frame past the master cylinder, located below the floorboard. To protect the surrounding components from the heat from this pipe I found this clamp-on heat shield made by Thermo Tec.
Clamp-On Heat Shield: Clamp-On Heat Shields incorporate Thermo-Tec's Thermal Conduction Technology. The flexible Clamp-On Heat Shield blocks over 95% of the damaging radiant heat of the exhaust. The kits come complete with all clamps and new stainless steel stand-offs that install in minutes.
Clamp-On Heat Shields are available in one, two and three foot lengths. For exhaust pipes that exceed 3.5-inch OD, use the 4-inch clamps that will accommodate up to 4.5-inch OD pipes. For motorcycle and applications involving smaller pipe, consider the #11650 and #11660 that are designed for 2-inch diameter exhaust.
Included in the kit is the Kevlar shield with the riveted stand-offs and stainless steel hose clamps.
Clamps are routed through the stand-offs as shown, in preparation for mounting.
Ends of the clamps are inserted into the clamp after they have been wrapped around the pipe. They can be tightened with a screwdriver or the proper size socket and wrench.
The combination of the clamps and standoffs maintain an air space between the pipe and the shield making them much more effective than just wrapping an insulator around the pipe.
This shot from above shows how close the pipe is to the master cylinder and other brake components.
View from below reveals that there is more clearance at the sides and the way the clamp-on shield was oriented to deflect the heat. Additional clamp-on shields could be added at any time if other areas in need of heat control are discovered.
Thermo Tec also produces a wide variety of exhaust insulating wraps, heat barrier shields, insulating mats, sleeving products and acoustical mats. Something for every thermal protection problem.