If you cut your teeth on small-block or big-block Chevys and are now playing with LS engines, you may wonder why the LS needs steam lines plumbed into as many as four corners of the cylinder heads.

Jeremy Stoermer from Holley Performance Products, which includes the Earl’s Performance Plumbing brand, explains in the video, in those older brothers to the LS, coolant flowed first through the engine before exiting the thermostat housing on top of the intake manifold.

Earl’s top-of-the-line LS steam tube kit includes braided stainless Speed-Seal hose, electroless nickel plated steel hose ends, adjustable steam vent adapters & distribution block, for the front and rear of the engine (four-corner).

Earl’s offers a number of custom solutions to the LS hot-rodder, from a basic OEM-style replacement to a custom setup featuring stainless steel braided lines.

In an LS engine, because the thermostat is in the water pump housing, it is located much lower on the engine than on big-blocks and Gen-1 small-blocks, Stoermer explains.

As this Earl’s graphic shows at top left, an air pocket can mean engine hot spots because of poor coolant flow in that area.

“With the LS design, the temperature and flow of the coolant are regulated before the coolant ever enters your engine,” Stoermer says. “The catch with the LS engines is the thermostat is positioned at a point lower than most of the coolant passages in the engine itself, and any air that enters the system can get trapped, forming bubbles in the coolant.”

Over time, Stoermer says, those bubbles accumulate, forming an air pocket that prevents the continuous flow of coolant. Since air cannot dissipate heat as well as a liquid, this creates problem areas known as hot spots.

“They can cause overheating and more serious issues, such as detonation and pre-ignition within the cylinder, which will eventually cause damage to your engine.”

The catch with the LS engines is the thermostat is positioned at a point lower than most of the coolant passages in the engine itself, and any air that enters the system can get trapped, forming bubbles in the coolant.–Jeremy Stoermer, Holley Performance Products

Steam ports, and their associated lines, two in the front for later LS engines and four (two in the front and two in the back) for earlier models, remove this trapped air. For custom installations, Stoermer says, the steam ports need to be connected and run to either a fitting in the radiator or a tapped port on the water pump housing.

Earl’s offers kits for two- and four-port setups in a choice of black push-on, black Pro-Lite 350, or stainless steel Speed-Flex hose. The more comprehensive kits also include low-profile, adjustable port adapters, which better accommodate aftermarket intakes and accessories. A dual-outlet option even eliminates the need for a tee adapter.

The original GM brazed vent tube manifold does not take into consideration the aftermarket intakes and accessories we put on our performance vehicles. Replace the rigid hard lines with these adjustable outlet, O-ring seal adapters that converts to -3 or -4 AN plumbing. Earl’s Steam tube adapters are the most adjustable and lowest profile available. These adapters look as nice as they are installation friendly. There are 6 kits available to allow for the optimal routing on your application including at dual outlet option which eliminates needing a “T” adapter.

Custom installations in which the engine is installed higher at the front than the rear can get by with the two-port adapter kit, Stoermer advises, while installations in which the engine is level or nearly level should use the four-port kit.

“Our kits not only look better; they also offer you more adjustment over the factory units and complete flexibility when it comes to routing your hoses,” he says.