Why Do LS Engines Have Steam Tubes?

By: Jeremy Stoermer | 06/27/2019 < Back to Motor Life Home

What are these crazy looking tubes on my LS engine and why do I need them anyway?  

To better understand the use of steam tubes on today’s modern engines lets first take a look at the iconic small block Chevy engine. In the original small and big block engines, coolant first flows through the engine, before exiting through the thermostat housing that’s located on top of the intake manifold. Right here is where the thermostat is located and it controls the flow and temperature of the engine coolant. In an LS engine, the thermostat is in the water pump housing, which is locating much lower on the engine when compared to the old SBC set-up. With the LS design, the temperature and flow of the coolant is regulated before the coolant ever enters your engine.

The catch with LS engines is that the thermostat is positioned at a point lower than most of the coolant passages in the engine. Any air that enters the system can get trapped, forming bubbles in the coolant. These bubbles can accumulate over time and form a pocket of air that actually prevents the continuous flow of coolant. This trapped air takes up space in the cooling system that’s normally occupied by coolant. And since air can’t dissipate the heat like a liquid can, this creates problem areas commonly known as hot spots, which can cause overheating and more serious issues like detonation and pre-ignition within the cylinder that can eventually damage your engine.

To remove this trapped air from the cooling system, GM added steam ports to the cylinder heads. Most early LS engines utilized 4 ports, 2 in the front and 2 in the back of the heads. If your engine has 4 steam ports or you’ve done an LS swap and positioned the engine level or near level in the chassis, we can help you complete your installation with one of our complete 4 port adapter kits. Later LS engines typically only use 2 steams ports, which are located at the front of the cylinder heads. So if your installation has the front of the engine elevated higher than the rear, you can get by with a 2 port adapter kit. We offer kits for 2 port set-ups with your choice of black push-on, black pro-lite or stainless steel speed-seal hose and they come with our adjustable port adapters. Our kits not only look way better, they offer you more adjustment over the factory units and complete flexibility when it comes to routing the hoses.

The steam ports need to be connected together and run back to either a fitting in the radiator or a tapped port on the water pump housing. Steam ports allow coolant to flow to the highest points of the engine, removing any trapped air and helping to keep your engine running cooler. So whether you're doing an LS swap that requires an upgrade to a 4 port system or just want to dress up that factory engine bay. Earls’ can help you keep your cool with our 2 and 4 port steam adapter kits.

For more information on our complete line-up of steam tube adapter kits, visit our website at

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