GM 12561873 Assembled Ls Cast Iron Cylinder Heads LQ4 6.0L

( Brand: Gm ), ( Manufacturer Part Number: 12561873 ), ( Material: Cast Iron ), ( Type: Cylinder Head Assembly ), ( Items Included: Pair Of Oem Assembled Cylinder Heads ), ( Vintage Part: No ), ( Finish: Unfinished )

Review GM Used Assembled Pair Ls 873 Cast Iron Cylinder Heads Lq4 6.0l Truck Free Ship

The **GM 12561873 Assembled LS 873 Cast Iron Cylinder Heads** are a high-performance, factory-specified component designed exclusively for the **6.0L LS8 V8 engine**, a legendary powerplant renowned for its durability, raw torque, and racing pedigree. Crafted from premium **cast iron**, these heads are engineered to withstand the extreme demands of both street and track applications, offering an ideal balance of strength, heat dissipation, and efficiency. The **LS 873** designation signifies their direct compatibility with the **LS8 engine**, which powers iconic vehicles like the **2007 2009 Chevrolet Corvette Z06** and the **2007 2009 Cadillac CTS-V**, as well as aftermarket builds seeking the pinnacle of LS engine performance. These heads feature a **fully assembled configuration**, complete with **intake and exhaust valves**, **valve springs**, **valve guides**, **valve seals**, and **retention hardware**, ensuring immediate installation readiness upon receipt. The **intake ports** are meticulously designed for optimal airflow, while the **exhaust ports** are optimized for high-flow performance, reducing backpressure and enhancing power delivery across the RPM spectrum. The **combustion chambers** are precision-machined to meet GM s exacting specifications, promoting efficient fuel combustion and minimizing detonation risk. Additionally, these heads incorporate **modern valve train components**, including **solid lifters** (in the case of the LS8 s pushrod-driven design) and **high-strength retainers**, which contribute to the engine s legendary reliability under extreme loads. Whether integrated into a **high-performance street rod**, a **drag racing application**, or a **restomod project**, these cylinder heads deliver the raw, unfiltered power that the LS8 is famous for making them a must-have upgrade for enthusiasts seeking to unlock the full potential of their 6.0L V8.

### **Pros and Cons of Buying Assembled GM 12561873 LS 873 Cast-Iron Cylinder Heads (LQ4 6.0L)**

#### **Pros**

1. **Proven Reliability** Cast-iron heads are known for their durability and resistance to warping, making them a solid choice for high-performance and daily-drive applications. The LS 873 design has been widely used in GM engines since the early 2000s, with extensive aftermarket support and proven longevity.

2. **Better Heat Dissipation** Cast iron conducts heat more effectively than aluminum, which can help prevent overheating in high-performance or heavily modified engines. This is particularly beneficial for forced-induction applications (turbo/supercharged) where thermal management is critical.

3. **Compatibility with Stock and Modified Engines** These heads are designed for the LQ4 6.0L engine (found in the Corvette C5-R, Z06, and some LS3 applications), meaning they will bolt-on directly without major modifications. They are also compatible with aftermarket camshafts, lifters, and valve springs, making them versatile for both stock and built engines.

4. **Aftermarket Support** The LS platform has an extensive aftermarket, including ported heads, custom valve jobs, and high-flow intake/exhaust manifolds. This means you can further optimize airflow and performance if desired.

5. **Cost-Effective for Long-Term Use** While the upfront cost may be higher than aluminum heads, cast iron s durability can reduce long-term expenses related to head gasket failures, warping, or replacement cycles, especially in high-mileage or aggressive driving scenarios.

6. **Better for High Compression Ratios** Cast iron can handle higher compression without the risk of catastrophic failure (e.g., head cracking) that sometimes occurs with aluminum under extreme loads.

7. **Easier to Machine and Modify** If you plan to port or modify the heads yourself, cast iron is generally easier to machine than aluminum, though it requires heavier tools.

---

#### **Cons**

1. **Higher Weight** Cast iron heads are significantly heavier than aluminum, which can increase rotating mass and slightly reduce engine responsiveness, especially in high-revving applications. This is less noticeable in a 6.0L engine but may be a consideration in extreme builds.

2. **Slower Heat Transfer to Coolant** While cast iron handles heat well internally, it transfers heat to the coolant more slowly than aluminum. This can lead to slightly higher operating temperatures unless the cooling system is robust (e.g., upgraded radiator, thermostat, or water pump).

3. **Limited High-Performance Potential Without Mods** Stock cast iron LS heads are not as flow-efficient as high-end aluminum heads (e.g., LS9, LS7, or aftermarket aluminum heads). To unlock significant power gains, you ll likely need to port the heads, upgrade valves/seats, or install aftermarket manifolds.

4. **Potential for Carbon Buildup** Cast iron heads can be prone to carbon deposits, especially in high-compression or direct-injection applications. Regular maintenance (e.g., carbon cleaning) may be required to prevent performance loss.

5. **Higher Initial Cost** Compared to aluminum heads, cast iron LS heads are more expensive upfront, though they may save money in the long run by avoiding frequent replacements.

6. **Less Common in Modern Applications** While still widely used, cast iron heads are less common in newer high-performance builds where lightweight aluminum is preferred. This means fewer specialized parts (e.g., custom manifolds) may be available compared to aluminum heads.

7. **Potential for Quenching Issues** If the heads are not properly quenched or have stress risers (e.g., from machining), they can be prone to cracking under extreme loads (e.g., forced induction). This risk is mitigated with high-quality assembly and proper installation.

---

### **Ending Conclusion**

The **GM 12561873 LS 873 cast-iron cylinder heads** are an excellent choice for a **reliable, durable, and high-performance foundation** for your LQ4 6.0L engine. They excel in **stock, modified, and forced-induction applications** where longevity and heat management are priorities. While they are heavier and require more aftermarket tuning for maximum airflow, their proven track record and compatibility with the LS platform make them a **strong recommendation** for most builders.

If your primary goals are **durability, ease of maintenance, and a balance of performance and reliability**, these heads are an ideal pick. However, if you re targeting **extreme high-performance levels (e.g., 1,000 HP with forced induction)**, you may want to consider pairing them with **ported manifolds, upgraded valves, or even aftermarket aluminum heads** for better airflow.

For most **Corvette C5-R, Z06, or LS3 builds**, these heads are a **solid, no-regrets choice** that will serve you well for many miles.

---

### **Final Recommendation**

- You want a **durable, long-lasting** solution for your LQ4 engine.

- You plan to run **stock or mildly modified** power levels (e.g., 400 600 HP naturally aspirated, 600 800 HP with mild forced induction).

- You prioritize **reliability over absolute maximum airflow** (though porting can help).

- You re working within a **budget-conscious** but **high-quality** approach.

- You re targeting **extreme power levels** (800 HP) and need every bit of airflow.

- You prefer **lighter heads** for better revving characteristics.

- You re building a **highly modified engine** and want the best possible flow potential.

For the average builder, these heads are **one of the best stock replacements** available for the LS platform. Pair them with a **good port-and-polish job, upgraded valves, and a strong cooling system** to maximize their potential.

Details:

Key Details: Pair of heads left right matched set. Note: Although these heads were removed from a running engine, they have not been disassembled for any further inspection other than what you see with the naked eye. All there and functional. Compatibility: Direct fit for 1999 2000 LQ4 6.0L trucks Silverado, Suburban, etc. ; works on many Gen III LS engines may need minor mods some swaps.

Stock specs: 71cc chambers 9.5:1 CR on LQ4, 2.00 intake / 1.55 exhaust valves, decent flow potential. Great starter heads or for porting, milling, boosted projects. Assembled: Valves/seats good no visible damage/burnt, springs intact, retainers/locks present. These are the early iron cathedral-port heads casting #12561873 / 873 complete and assembled: valves, springs, retainers, locks, etc.

Used assembled pair of OEM GM 873 cast iron cylinder heads from a 1999 2000 LQ4 6.0L LS truck engine pulled running setup. Solid for budget LS builds, turbo/supercharged setups iron handles boost well, or swaps where you want durability over lightweight aluminum. Condition: Good used light surface rust/patina typical for iron heads in engine, no cracks/war page visible, ports/runners clean-ish, ready to clean/install.

part #: 12561873 prices

• $295.00-$399.99

specifications cylinderheapar:

• brand: Gm
• mpn: 12561873
• material: Cast Iron
• type: Cylinder Head Assembly
• items included: Pair Of Oem Assembled Cylinder Heads
• vintage part: No
• finish: Unfinished

offer cylinderheapar:

• options: Ship-to-home
• availability: In Stock
• sold: 0
• best offers: True
• quantity: 1
• started: March 20, 2026

general cylinderheapar:

• Car Truck Parts Accessories > Engines Engine Parts > Cylinder Heads
• condition: Used

seller cylinderheapar:

• city: Jefferson City, Missouri
• # reviews: 207
• rating: 100.0%

payments cylinderheapar:

• wallet: Google-pay
• credit card: Visa
• other

shipping cylinderheapar:

• class: Standard
• service: FedEx Ground / FedEx Home Delivery
• cost: $0.00
• carrier: FedEx
• transit: 3-6 Days
• type: Calculated

returns cylinderheapar:

• policy: No Returns

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