CHEVROLET 3986339 Cylinder Heads 1.94/1.5 74CC

( Brand: Chevrolet ), ( Manufacturer Part Number: 3986339 ), ( Type: Cylinder Head ), ( Material: Cast Iron ), ( Vintage Part: Yes ), ( Country Of Origin: United States ), ( Item Weight: 55 Lbs. Each )

Review CHEVROLET Pair Sbc Chevy Cylinder Heads 1.94/1.5 74cc fits 350 1970

The **1970 Chevrolet 350 cubic inch small-block cylinder heads** (part number **3986339**) are a highly sought-after and iconic component from one of the most legendary engine families in automotive history the legendary **L98 350 CID small-block V8**. These heads, designed for the **1970 model year**, represent a transitional yet robust iteration of Chevrolet s small-block architecture, blending performance potential with the early restrictions of emissions regulations. Crafted from **cast iron**, these heads feature a **1.94-inch intake valve** and a **1.5-inch exhaust valve**, dimensions that strike a balance between airflow efficiency and durability, allowing for both street driving and mild performance applications. The **74 cubic-inch combustion chamber volume** (measured at .030-inch deck clearance) is a hallmark of this era, offering a sweet spot for compression ratios that can be tuned for either high-performance fuel or mild ethanol blends, depending on the application. The **port design** is classic for its time, with smooth, slightly tapered intake ports that promote strong airflow at moderate RPM ranges, while the exhaust ports maintain a robust, high-velocity exit for efficient scavenging. These heads are often paired with the **L98 350** a high-performance variant of the 350 small-block though they are also compatible with other 350 CID engines from the same era, including the **L34** and **L36**, making them a versatile choice for restorers and enthusiasts. The **deck surface** is machined to a precise flatness, ensuring a proper seal with the cylinder block when paired with a suitable gasket, while the **valve guide spacing** and **bolt pattern** align seamlessly with the 350 small-block s proven design. Whether you re building a classic muscle car, a high-performance street machine, or a reliable daily driver, these **1970 Chevrolet 350 cylinder heads** deliver a blend of authenticity, performance potential, and timeless engineering that continues to captivate the hearts of small-block enthusiasts.

### Pros and Cons of Buying 1970 Chevy 350 Cylinder Heads (3986339, 1.94/1.5, 74cc)

1. **Performance Potential** These cylinder heads are designed for the iconic 350 cubic inch Chevy V8, which is a popular engine for muscle cars, street rods, and custom builds. The 1.94-inch intake and 1.5-inch exhaust valves, combined with a 74cc combustion chamber, allow for good airflow and potential for modifications like porting, polishing, or installing larger valves for increased horsepower.

2. **Compatibility** The part number (3986339) is a well-documented Chevy small-block head, meaning there are plenty of aftermarket parts, gaskets, springs, and valves available. They fit standard 350 engines, making them a reliable choice for restorations or performance builds.

3. **Durability** Cast iron heads like these are known for their strength and longevity, especially when properly maintained. They can handle high compression ratios and forced induction (if modified) better than some aluminum alternatives.

4. **Cost-Effective** Compared to brand-new or high-performance aftermarket heads, these factory heads are relatively affordable, especially if sourced from a reputable used parts dealer or salvage yard.

5. **Aesthetic Appeal** For classic car enthusiasts, original or restored factory heads add authenticity and a vintage look to a build, which can be valuable for show cars or concours entries.

6. **Modification Flexibility** These heads can be ported, polished, or upgraded with performance internals (such as stainless steel valves, stronger springs, or high-flow exhaust manifolds) to significantly improve engine performance.

7. **Widespread Availability of Parts** Since these heads are from a classic engine, you ll find an extensive selection of OEM and aftermarket parts, including gaskets, bolts, springs, and even complete head assemblies if needed.

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1. **Potential for Wear or Damage** If the heads are salvaged or from an unknown source, they may have cracks, warping, or internal damage (such as burned valves or seat recession). Always inspect them thoroughly before purchasing.

2. **Age and Corrosion** Older heads may suffer from rust, pitting, or corrosion, especially if they ve been sitting in a junkyard for years. This can lead to leaks or reduced performance if not addressed.

3. **Stock Performance Limitations** Out of the box, these heads are not high-performance. They may require porting, valve jobbing, or other modifications to achieve meaningful power gains. Stock heads can struggle with high compression or forced induction without upgrades.

4. **Gasket and Seal Issues** Chevy small-block heads are notorious for leaking around the gasket area, especially if the gasket is old or improperly installed. Replacing gaskets and using high-quality sealants can be necessary.

5. **Valvetrain Wear** The stock valvetrain (pushrods, rocker arms, springs) may be worn out, requiring replacement if the engine is being rebuilt or heavily modified.

6. **Weight** Cast iron heads are heavier than aluminum alternatives, which can slightly reduce high-RPM performance and acceleration in high-performance applications.

7. **Learning Curve for Modifications** If you re not experienced with engine work, porting, or valve jobs, these heads may require professional help to unlock their full potential, adding to the cost.

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Buying these 1970 Chevy 350 cylinder heads (3986339, 1.94/1.5, 74cc) is a solid choice for enthusiasts looking to restore or modify a classic 350 engine. They offer a balance of affordability, durability, and performance potential, especially with the right modifications. However, they require careful inspection, potential refurbishment, and an understanding of their limitations particularly if you plan to push them beyond stock performance levels.

If you re building a street rod, a daily driver with mild modifications, or a show car, these heads are a great foundation. If you re aiming for extreme power (e.g., 600 horsepower), you may need to invest in aftermarket heads or significant upgrades.

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- **Buy if:** You need reliable, budget-friendly heads for a classic 350 build, plan to modify them (porting, valve job, etc.), and are willing to inspect them thoroughly for damage.

- **Avoid if:** You want plug-and-play high-performance heads without modifications, or if you re unsure about the condition of the heads (always get a visual inspection or test for leaks/cracks).

- Purchase from a reputable source (e.g., a trusted junkyard, salvage yard, or online seller with good reviews).

- Have them professionally inspected for cracks, warping, or internal damage.

- Consider porting and polishing for better airflow if you want improved performance.

- Replace gaskets, bolts, and springs to ensure a leak-free and reliable setup.

- If building for high performance, research whether aftermarket heads (e.g., Edelbrock, Holley, or high-flow aluminum heads) might be a better long-term investment.

For most classic car projects, these heads are a practical and cost-effective choice when properly prepared.

Details:

Pair 3986339 SBC 350 1970 Chevy Cylinder Heads 1.94/1.5 74cc Hardened Exhaust Seat inserts installed for Unleaded Fuel NEW 1.940 Intake Valves 1.5 Beehive Valve Springs Born on20 70 / 31 74 CC Chambers Resurfaced Decks Guides Machined Positive Teflon valve seals 3 Angle job Chased all threads Spring Pressure is 110 lbs. Valve closed 1.700 installed. Shot blasted, hot tanked .

part #: 3986339 prices

• $275.00-$425.00

specifications cylinderheapar:

• for models: 350
• for makes: Chevy, Chevrolet
• for years: 1970
• brand: Chevrolet
• mpn: 3986339
• type: Cylinder Head
• material: Cast Iron
• vintage part: Yes
• country of origin: United States
• item weight: 55 Lbs. Each

offer cylinderheapar:

• started: February 4, 2026
• options: Ship-to-home
• sold: 0
• quantity: 1
• availability: In Stock

seller cylinderheapar:

• rating: 100.0%
• # reviews: 3683
• city: Needmore, Pennsylvania

returns cylinderheapar:

• policy: No Returns

general cylinderheapar:

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

shipping cylinderheapar:

• type: Fixed
• class: Standard
• service: UPS Ground
• transit: 3-7 Days
• cost: $130.00
• carrier: UPS

payments cylinderheapar:

• wallet: Apple-pay
• credit card: Discover
• other

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