GM LS Stainless Steel Crossover Steam Vent Kit

• Routes trapped steam and air from all four corner ports on each cylinder head

• Stainless steel lines resist heat and corrosion in demanding engine bay conditions

• Fits Gen III/IV LS cylinder heads with 4 corner steam holes — verify before ordering

• Five-branch aluminum manifold consolidates venting into a single connection point

This stainless steel crossover steam vent kit routes trapped steam and air away from the cylinder heads on GM Gen III/IV LS engines, helping maintain consistent coolant flow and reducing air pockets in the cooling system. Stainless steel lines connect to a five-branch aluminum manifold, consolidating venting from all four corner steam ports into a single outlet.

Fitment depends on your cylinder heads having all four corner steam holes open — not on a specific engine code. This kit works on both cathedral-port and square-port LS heads, but some factory LS heads have the rear steam holes blocked rather than open. Since there's no reliable way to determine this by engine code alone, inspect your heads for four open corner steam holes before ordering.

Cylinder Head Compatibility
This kit fits Gen III/IV LS cylinder heads — cathedral-port or square-port — that have all four corner steam holes open. Some factory LS heads have the rear steam holes blocked from the factory; since this varies and isn't reliably tied to a specific engine code, physically check your heads for four open corner ports before ordering rather than relying on engine displacement or code alone.

Installation
The five-branch manifold consolidates steam vent lines from all four head ports into a single connection point, routing trapped steam and air out of the cooling system. Mounting hardware is not included, so plan your routing and mounting points before installation.

Will this fit my specific LS engine?
Fitment depends on the cylinder-head steam-port configuration, not just the engine code. This kit works with both cathedral-port and square-port LS heads, provided the required four corner steam ports are open. Inspect your cylinder heads before ordering.

How do I know if my heads have four open corner steam holes?
Visually inspect both cylinder heads and confirm that the front and rear corner steam ports are open. Don't rely solely on engine code or intake-port shape, as steam-port configurations can vary between LS cylinder heads.

Does this fit both cathedral-port and square-port LS heads?
Yes — it can work with cathedral-port or square-port LS heads as long as the required corner steam ports are open. Intake-port shape does not determine fitment for this kit.

What if my rear steam holes are blocked?
This kit is designed for a four-corner steam-port configuration. If your cylinder heads have factory-blocked rear steam ports, the kit cannot be installed in its intended four-corner configuration without additional modification.

Does this kit include mounting hardware?
No — mounting hardware is not included. Plan your line routing and mounting locations before installation.

What does the five-branch layout connect to?
The five-branch aluminum manifold consolidates the stainless steel steam vent lines from the cylinder heads and provides a common connection point for routing the vented coolant/air back into the cooling system.

Is this necessary for a stock LS engine, or only performance builds?
It's not required for every stock LS engine. Four-corner steam vent systems are most commonly used on performance builds, engine swaps, and modified cooling systems where improved evacuation of trapped air and steam from the cylinder heads is desired.