Why do LS engines have steam tubes? – Jalopnik

When the all-new fifth-generation Chevrolet Corvette premiered in 1997, it was equipped with an also all-new LS1 V8 engine that produced 345 hp and 350 Nm of torque – which was enough to propel the car from 0 to 60 mph in 4.9 seconds and to 100 mph in 11.4 seconds. The mighty mill also covered the quarter mile in 13.4 seconds at 107 mph. According to Car and driverwho performed the measurements, the 1997 Corvette was therefore 0.2 seconds faster, with a 4 mph higher trap speed, than the fastest previous generation Corvette with its previous generation V8. Today, however, some modern V6 engines put the LS1 to shame.

The thing is, a lot went into the LS1 to help achieve those numbers, including the all-aluminum design, upgraded intake/exhaust ports, drive-by-wire throttle and of course the steam tubes. The steam tubes are an essential part of the engine’s cooling system and were necessary due to the innovative design of the LS1. Yes, the LS1 was extremely powerful and efficient for its time, but the thermostat sat lower than most coolant passages, allowing air to build up in the cooling system.

To solve the problem, GM engineers added steam tubes to the engine. These basically allow trapped air to leave the cooling system so they don’t damage your engine. Consider it a method to let off some steam before your engine explodes.

To fully understand what happened, let’s take a look at the GM V8s from before the LS1 was introduced. The thermostats in these old cars – which help regulate the flow and temperature of the coolant – were installed after the coolant had already passed through the block and were physically placed at the top of the engine. The LS1 had its thermostat in a place where it caught the coolant before it entered the engine. To be precise, the LS1 thermostat is placed in the same housing as the water pump. However, that housing was located at the bottom of the engine.

Keep in mind that it is both easy for air bubbles to develop in a cooling system and extremely dangerous. They prevent a consistent flow of coolant: basically, the coolant cannot cool the air in the bubbles, potentially leading to hot spots that in turn can lead to major problems like detonation and pre-ignition. To address this, many thermostats have bleed valves/rocker pins that allow the air bubbles to escape. But because the air wants to rise, having those valves/pins in a thermostat on the bottom of the engine isn’t very effective.

So the LS1 steam tubes connect the low thermostat to special steam ports higher up in the block, creating a route for the air to escape. The first LS1 engines had four steam ports, while later versions had two.

The original LS1 quickly expanded its reach to the General’s 1998 muscle cars: the Chevrolet Camaro and Pontiac Firebird. However, an unofficial rule at GM was that no other car could be as powerful as the ‘Vette, so the Camaro and Firebird were limited to 330 horses, five fewer than the Corvette, in their most popular configurations.

The next big step forward was the LS6 V8 launched in 2001, again on a Corvette: this time it was the Z06 fresh from the factory with 385 horsepower/385 pound-feet of torque. The LS6, which was also used for the 2004-2005 Cadillac CTS-V models, remained in production until 2005, when the LS2 first appeared.

The LS2 came with a significant upgrade in displacement, from the 5.7 liters of the LS1 and LS6 to 6.0 liters, and was joined by a 7.0 liter LS7 in 2006 and a 6.2 liter LS3 in 2008. Now those were all naturally aspirated mills, but the LS family welcomed forced induction in 2009 with the supercharged LS9. It powered the very first Corvette to reach a speed of more than 200 miles per hour, that year’s Corvette ZR1. GM obviously detuned the engine a bit for the 2009 Cadillac CTS-V, renaming it LSA.

LSA engines remained in the mix until the Chevrolet ZL1 sailed into the sunset in 2015 – even though it’s 39 times more likely to be stolen than the average car.