While excessive heat around your spark plugs is rarely a problem in a stock, road-going vehicle usually easily managed by the OEM heat shields, when you start modifying the engine for horsepower, and particularly with the use of forced induction, that fact begins to change. And in the case of full-on race machinery, where exhaust temperatures near the flange can well exceed quadruple digits, this is especially the case.
For such applications, aftermarket spark plug heat shields are an absolutely necessity, because as the exhaust temperatures rise to red-hot levels, the spark plug boot and wires can overheat and enter a ‘burnout’ situation, where misfires and a loss of performance can occur, and even melt and leak the spark to the ground in worst-case scenarios.
To combat this, a number of manufacturers produce heat shields and spark plug boot/wire covers using various materials to limit the amount of heat that the wires are exposed to during engine operation. One of the more interesting materials out there is basalt, which if you will recall from your high school science courses, is actually a volcanic igneous rock. But how does a rock become a flexible, fiber-like heatshield? We asked Steve Heye of Heatshield Products — which markets their Lava Boot heat shields made of basalt, along with a whole range of heat-management products — that very question.
This [basalt] was something used in the Russian military days, as they were looking for something to compete with Kevlar and Nomex — something that was really high-strength. – Steve Heye
In the early 2000s, the use of basalt came around again in the insulation business, and Heatshield Products took a look at using it for their automotive products. From that, the Lava Boot and other heat-shielding products were born.
Basalt, a liquid mineral that comes from volcanic magma at upwards of 2,000 degrees, turns to a solid when it cools down. According to Heye, the mineral is then mined and super-heated to seat the different components of the magma. It’s eventually crushed down and turned into a fiber by winding it into very fine threads. It is, as he puts it plainly, a mineralized fiber.
The Heatshield Lava Boots can safely manage 1200 degrees Fahrenheit of continuous operating temperature, and 2000 degrees intermittent, which serves very well in a drag racing application where heat reaches a peak for only a short period of time. The Lava Boots are designed with LS engines in particular in mind, where the need for longer boots are necessary to protect the wire that’s typically snaked near the header tube up to the coil packs atop the valve cover. In such applications, spark plug burnout can be common without protecting them.
The Lava Boots have a universal design to fit most spark plug boots and angles, including full 90-degree boots. Both a standard six inch size and an 8-1/2-inch long, 1-1/14-inch internal diameter shield for LS engines are available. Heye recommends the Lava Boot shields for anyone running headers that angle up out of the exhaust port, sitting in close proximity to the spark plug wires. As well, anything with forced induction, be it a supercharger or turbocharger, will develop the kind of exhaust-gas temperatures requiring extra spark plug wire protection. But, be it hardcore street cars, drag racers, road course ringers, offroad racers, or any other performance application, one can benefit from the peace of mind of spark plug boots.
“The nice thing about basalt versus fiberglass boots is that basalt is very strong. It’s 25% stronger than fiberglass, and a little bit better at reflecting heat, and more efficient at displacing the thermal energy. But that’s great about it is that it can be be so flexible and stay strong, even at temperature.”
To install the heatshields, you simply slide open end of the Lava Boot onto the spark plug boot, and press firmly to ensure contact is made. Inside is a ring that’s designed to rest between the cylinder head and the tip of the spark plug boot, to prevent it from walking up the wire. For LS motors, one may need to remove the factory metal shield around the spark plug boot, if it’s still present.