Intake Manifold Heatshield

By Dino Savva

The aluminium intake manifold sits above the exhaust header on the Jeep 4.0 I6 engine and becomes extremely hot during normal running. The intake air inside the manifold becomes heated before it enters the cylinders, especially at idle and at low speeds when airflow is slow. Hot air is less dense and reduces horsepower/torque output (1% less HP/TQ for every 11*F rise in IAT).
I decided to install a heatshield on the underside of my intake manifold to block out the radiant heat from the header. I bought a 12" x 24" Thermotec adhesive-backed aluminised heat barrier #THE-13575 from Summit Racing.

Thermotec Barrier

The Adhesive Backed Heat Barrier protects parts and components from radiant heat. It can be used in applications to protect painted surfaces, plastic parts or any component from the damaging effects of radiant heat. Aluminized Heat Barrier is made up of woven silica with a flexible aluminized finish. The highly reflective surface of the material is capable of withstanding radiant temperatures in excess of 2000F. The adhesive backed composite construction material can easily be applied to any surface or wrapped around a hose or wire to make a clean professional appearance.

Installation and Results

I cut 2" off the width to leave it at 10" x 24" for installation. I took off the adhesive backing and manipulated it into place on the underside of the intake manifold covering the whole area. I then used the Thermotec stainless steel snap straps from Summit Racing #THE-13002 to make it doubly secure. The reflective surface faces downwards. The whole process took just a 1/2 hour.
Did it reduce the underhood air and intake manifold temps.? Yes, and quite a bit too! I took some temp. readings with the probe of my digital thermometer secured onto the IAT sensor before and after doing this mod. I took readings at a steady 20mph, 40mph and 60mph with the outside temp. at 95*F each time. The results were as follows:

Idle: Without heatshield-increases in seconds to 160+*F, With heatshield-much slower rise in underhood temp.
20mph: Without heatshield 157*F
With heatshield 132*F
40mph: Without heatshield 139*F
With heatshield 122*F
60mph: Without heatshield 127*F
With heatshield 121*F

That's enough to produce a rear wheel torque gain of 4lbft at 1000rpm, 2.5lbft at 1500rpm, 1.5lbft at 2000rpm, and 1lbft at 2500rpm.
The intake manifold is definitely cooler. I can actually touch it for a couple of seconds without getting my fingers burnt. The engine compartment is also cooler so electrical and other components will have an easier time. This is a great cheap mod and I highly recommend it.