GM AC175C8 Cylinder Head 2.5 Head. 485 514

( Brand: Gm ), ( Manufacturer Part Number: AC175C8 ), ( Type: Cylinder Head ), ( Items Included: 1 Remanufactured Cylinder Head ), ( Material: Cast Iron ), ( Finish: Remanufactured ), ( Country Of Origin: United States ), ( Item Weight: 45lb ), ( California Prop 65 Warning: May Contain Chemicals Known To The State Of California To Cause Cancer Or Birth Defects )

Review GM Remanufactured 2.5 Cylinder Head. Casting #485 514 Vin

The **GM AC175C8 2.5L Cylinder Head (Part Numbers 485 and 514)** is a critical component of General Motors 2.5L inline-four engine family, specifically designed for applications such as the Chevrolet Cavalier, Pontiac Sunfire, Saturn SL, and other models from the late 1990s and early 2000s. This cylinder head is engineered with precision to deliver reliable performance while maintaining efficiency and durability, making it a cornerstone of the engine s overall functionality. Crafted from high-quality cast iron, the head features a robust design that ensures proper heat dissipation and structural integrity under high-temperature operating conditions, which is essential for preventing warping or cracking over time. The head incorporates a **four-valve-per-cylinder design**, with each cylinder featuring two intake and two exhaust valves, allowing for optimized airflow and improved combustion efficiency. The valve train is supported by **hydraulic lifters**, eliminating the need for manual adjustment and reducing maintenance requirements while minimizing wear on the camshaft and pushrods.

The **AC175C8** cylinder head is compatible with both **fuel-injected and carbureted** versions of the 2.5L engine, though it is most commonly found in fuel-injected applications due to the widespread adoption of electronic engine management systems in modern vehicles. The head is equipped with **cast-in cooling passages** that work in conjunction with the engine s cooling system to regulate temperature, preventing overheating and ensuring consistent performance. The **spark plug holes** are strategically positioned for optimal ignition timing, while the **camshaft bearing caps** and **camshaft lobes** are machined to precise tolerances to minimize friction and maximize durability. The head also features **integrated oil passages** that lubricate the valve train, reducing wear on the rocker arms, valves, and valve springs.

For maintenance and replacement purposes, the **GM AC175C8** cylinder head is available in two primary variants: **Part Number 485**, which is the standard production head, and **Part Number 514**, a slightly revised version that may include minor design updates or manufacturing refinements. Both versions are fully interchangeable with the original equipment heads, ensuring a seamless fit for rebuilds, restorations, or performance upgrades. When installing this cylinder head, it is essential to use the correct **valve springs, retainers, and keepers**, as well as the appropriate **valve stem seals** and **spark plug gaskets**, to prevent leaks and ensure proper sealing. The head s **threaded spark plug holes** are designed to accept standard **NGK or Champion** spark plugs, though the exact specifications should be verified against the engine s original service manual.

This cylinder head is a key component for enthusiasts looking to restore or modify their 2.5L-powered vehicles, as it plays a vital role in maintaining engine performance, fuel efficiency, and longevity. Whether used in a **stock rebuild, high-performance build, or classic car restoration**, the **GM AC175C8 (485/514)** cylinder head provides the reliability and precision needed to keep the engine running smoothly for thousands of miles. Proper installation, including the use of **high-quality gaskets, proper torque specifications, and correct valve adjustments**, will ensure that this component performs at its best, delivering the power and efficiency that GM s 2.5L engines are known for.

### **Pros and Cons of Buying a GM AC175C8 2.5L Cylinder Head (485/514 Series)**

1. **Common and Widely Available** The AC175C8 is a well-known cylinder head design used in several GM engines (including the 2.5L L62/L63/L67/L68 in vehicles like the Chevrolet Cavalier, Pontiac Sunfire, and Saturn SL). This means parts, rebuild kits, and labor are readily accessible, reducing downtime and repair costs.

2. **Proven Reliability** When properly maintained, these cylinder heads are durable and can last well beyond 100,000 miles, especially if rebuilt with quality materials (seals, valves, springs, and gaskets). Many owners report smooth operation after a rebuild.

3. **Repairable and Upgradable** Unlike some modern heads that are welded or cast as single units, the AC175C8 has a removable rocker cover and individual valve springs, making it easier to service. Upgrades like stiffer springs, larger valves, or porting are possible for performance applications.

4. **Cost-Effective Rebuild** Compared to newer high-performance heads, rebuilding this design is relatively inexpensive. A full rebuild kit (including valves, springs, seals, and gaskets) typically costs between **$150 $300**, with labor adding another **$200 $400** depending on the shop. This is far cheaper than replacing an entire engine.

5. **Good for DIYers** The design is straightforward enough for experienced DIYers to rebuild at home with the right tools (valve spring compressor, torque wrench, and a clean workspace). Many step-by-step guides and videos are available online.

- **Performance camshafts** (e.g., Crane, Comp Cams)

- **High-flow intake and exhaust valves** (e.g., Scat, Valve Train Specialties)

- **Ported and polished heads** (for better airflow)

- **Upgraded oil pumps and lifters** (to reduce wear)

This allows for tuning and performance modifications without major engine overhauls.

7. **Long-Term Engine Protection** A rebuilt head prevents issues like **valve float, excessive wear, or coolant leaks** (common in older heads). Properly sealed and gasketed heads reduce the risk of catastrophic failure, which can be costly in these engines.

8. **Good for Classic and Street Rod Projects** If you re restoring a classic GM vehicle, this head is a reliable choice. Many enthusiasts prefer it over newer, more complex designs for its simplicity and track record.

---

1. **Potential for Leaks** The AC175C8 is known for **head gasket and oil cooler line leaks**, especially if the engine has high mileage or was previously neglected. The **oil cooler lines** (if equipped) are a common failure point. A thorough inspection of the block, head, and gaskets is essential before purchase.

2. **Worn Valvetrain Components** If the head has high mileage, the **valve springs, retainers, and guides** may be worn, leading to **valve float or excessive lash**. Replacing these is part of any rebuild, but neglecting them can cause **valve damage or engine misfires**.

3. **Head Warping Risk** Overheating (from poor cooling, incorrect torque specs, or a seized piston) can warp the head, leading to **uneven gasket compression** and leaks. Always check for warpage with a **straightedge and feeler gauge** before sealing.

4. **Limited High-Performance Potential** While upgrades are possible, the **stock porting is not aggressive**, and the **camshaft choices are limited** compared to modern high-performance heads. For serious power gains, you may need to **port the head** or switch to a more advanced design (e.g., LS-series heads).

5. **Oil Pump and Lifter Wear** The **rotor-style oil pump** and **mechanical lifters** in these engines are prone to wear, especially if oil changes were skipped. A rebuild should include **new lifters, oil pump, and oil filter housing gasket** to prevent future issues.

6. **Timing Chain Stretch** The **timing chain** in these engines can stretch over time, leading to **timing issues and poor performance**. While not directly related to the head, a chain replacement is often recommended alongside a head rebuild.

7. **Coolant System Vulnerabilities** The **thermostat housing and head gasket area** are common leak points. If the engine has a history of overheating, the **water jackets** may be corroded, requiring a **block inspection** before installation.

8. **Torque Specs Must Be Followed Precisely** Improper torque on **head bolts, rocker cover bolts, or oil cooler lines** can lead to **leaks or warping**. Many rebuilds fail due to **over-tightening**, so a **torque wrench is essential**.

9. **Limited Modern Support** While parts are available, some **OEM-specific components** (like exact-fit gaskets) may be harder to find compared to newer GM engines. Always verify compatibility before purchasing.

10. **Potential for Hidden Damage** If the head was previously damaged (e.g., **bent valves, cracked combustion chambers, or seized lifters**), it may require **more extensive repairs** than a simple rebuild. A **full inspection** (including **valve seat machining, deck surface check, and combustion chamber inspection**) is crucial.

---

The **GM AC175C8 2.5L cylinder head (485/514 series)** is a **solid, cost-effective choice** for reliable performance in classic and street applications. Its **widespread availability, repairability, and compatibility with aftermarket parts** make it a favorite among enthusiasts. However, it is **not without drawbacks** **leaks, wear-prone components, and the need for careful maintenance** mean that a **proper rebuild is essential** for long-term reliability.

- **Inspect it thoroughly** for warping, leaks, and internal wear.

- **Rebuild it with quality parts** (not just a cheap kit).

- **Follow torque specs precisely** to avoid future issues.

- **Maintain the engine properly** (regular oil changes, cooling system checks).

If you re **pursuing high-performance applications** (e.g., **500 HP**), you may need to **port the head, upgrade the camshaft, and consider a more advanced design** (like LS-series heads) for better airflow and durability.

You need a **reliable, budget-friendly rebuild** for a classic or street engine.

You re **willing to put in the effort** for a proper rebuild (or have a trusted mechanic do it).

You plan to **modify it moderately** (camshafts, valves, porting) for better performance.

The engine has **low to moderate mileage** (under 150,000 miles) with **no history of overheating or neglect**.

The head shows **signs of warping, cracks, or severe internal wear**.

The engine has **high mileage with no maintenance history** (risk of hidden damage).

You re **not comfortable with DIY repairs** and don t have access to a skilled mechanic.

You need **extreme power** (this head is not ideal for high-RPM or forced induction builds).

- **Get a professional inspection** before purchasing.

- **Rebuild it with a full kit** (valves, springs, seals, gaskets, lifters, oil pump).

- **Torque all fasteners correctly** to prevent leaks.

- **Monitor for leaks and wear** during break-in.

For most **budget-conscious, performance-focused GM 2.5L projects**, the **AC175C8 is a strong choice** **when treated with care**.

Details:

Head Cast #: 485, 514. All seats and surface are re-machined within.e. Sub model: BAJA. Sub model: BASE.

Specifications. Sub model: LIMITED. Sub model: EUROSPORT. Make: BUICK remove.

Complete head with valves and springs. Aspiration: NATURALLY ASPIRATED. Sub model: EL. Completely remanufactured cylinder head.

All heads are and guaranteed to be free from casting defects. Parts are inspected and refurbished to like new if within.e specification. Fitment Notes: Block Cast # 311/C7 514, 485. New parts are installed as needed.

All heads are vacuum tested to ensure proper valve seating.FREE SHIPPING inside the continental USA only. Sub model: TAHOE. Sub model: SPECIAL. FREE SHIPPING inside the USA.

All bolt holes are retreaded and repaired as needed. Sub model: SLE. Engine Type: L4 2.5L / 151. 1992 BUICK CENTURY.

Sub model: CUSTOM. Sub model: LE.

part #: ac175c8 price

• $250.00

specifications cylinderheapar:

• brand: Gm
• mpn: Ac175c8
• type: Cylinder Head
• items included: 1 Remanufactured Cylinder Head
• material: Cast Iron
• finish: Remanufactured
• country of origin: United States
• item weight: 45lb
• california prop 65 warning: May Contain Chemicals Known To The State Of California To Cause Cancer Or Birth Defects

general cylinderheapar:

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

shipping cylinderheapar:

• class: Standard
• service: FedEx Ground / FedEx Home Delivery
• transit: 3-9 Days
• type: Calculated
• carrier: FedEx
• cost: $0.00

returns cylinderheapar:

• policy: No Returns

offer cylinderheapar:

• quantity: 4
• sold: 0
• options: Ship-to-home
• started: April 8, 2026
• best offers: True
• availability: In Stock

seller cylinderheapar:

• city: Oakland, California
• rating: 100.0%
• # reviews: 12

payments cylinderheapar:

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

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