I have come to realize there is a lot of gray area and unanswered questions when it comes to cooling systems on LS1 engines, more notably when it comes to the coolant crossover or “steam ports” on Gen 3 and Gen 4 LS heads. General Motors design to have provisions for “coolant crossover” built in the heads was awesome, however, they did themselves an injustice by changing their factory offering from the early years of 4 corner style coolant crossovers to only connecting the front most two in later models.
I am by no means an expert when it comes to thermal dynamics, physics, or chemistry for that matter. However, cooling systems follow a lot of very basic principles. I will explain more below.
As temperature raises, so too does pressure, it is a direct correlation. Conversely, reducing pressure lowers overall temperature (i.e. relieving trapped steam in high corners such as where the steam vent/coolant crossover corners are in a head). A motor that has trapped steam pockets will cause higher engine temperatures, period.
Next, while the “steam” gets trapped in the corners of the heads, voids can be created where coolant would normally be doing its job. These airpockets cause the areas without coolant to superheat in comparison to the areas where water/coolant are present.
In addition to poor air/fuel distribution by some intake designs, one common reason why we see the furthest back cylinders (7 and 8) burn up far more than others is due to a highly elevated temperature caused by trapped steam pockets. These cylinders in the corners without proper steam ventilation (and therefore steam pockets) begin to have drastically different temperatures than other cylinders in the system. This different cylinder temperature requires a much different fueling strategy to create a safe living condition.
This problem is a scenario on Naturally Aspirated engines. Now consider the effect of adding higher cylinder temperatures, cylinder pressures, and therefore higher coolant system pressures. All effects on the engine are now magnified. Now that we understand the logic behind a 4 corner crossover system, lets talk more about details of the system. Click the link to see Motion Raceworks coolant crossover systems http://www.motionraceworks.com/store/c15/Cooling_System.html
As mentioned earlier, many Gen 4 model LS heads have the rear two coolant crossover ports are physically blocked off by a press in plug, this does not put you off the hook. These can be easily tapped out from the bottom side with a punch (they are just plugs) or can be drilled out carefully from the top. Do not look the other way because they are blocked from the factory.
The last topic I would like to introduce is where to deliver the return from your coolant crossover. I commonly get asked (where should I return to). My suggestion is always back to your radiator, as high up near the filler neck/cap as possible, this allows the cap to vent pressure as it builds. Have a friend weld an 1/8 NPT bung into your radiator, and run a -4 flex line directly from the top port of our 5 corner manifold directly to your radiator. This helps to insure that the steam or air pockets in your system are not reintroduced to the coolant.
In summary, adding a four corner coolant crossover system to your ls engine is going to help balance your tuneup overall, reduce engine temperatures, improve your cooling system efficiency, and increase the longevity of your engine.
Motion Raceworks coolant crossover systems are engineered to perform, we hand build all of our hard line kits and test fit prior to shipment. Both our hard line and our flexline kit will optimize your cooling system and all components are MADE IN THE USA! Our all new flex line kit allows folks with plastic manifolds where they cannot run a traditional or stock under intake setup to have 4 corner crossover capabilities. We have kits for both stock intakes with stock rails and those with aftermarket rails, as well as FAST intakes.
Our hardline kits are known to work below the following LS intake manifolds:
Gen 3 stock truck plastic
Edelbrock Victor Jr
Edelbrock Super Victor
Holley single plane
GM single plane
Holley Mid Ram
Holley HI Ram
Edelbrock Pro Flo
*Most any other single plane on the market*
Please feel free to call or email Motion Raceworks with any questions. (563) 345-7223 or firstname.lastname@example.org