Chevy 350 Gear Drive: Installation and Benefits

JEGS Tech Specialist

Pete Mitchell

A gear drive timing set is a proven upgrade for performance engines, particularly in high-revving small blocks like the Chevy 350. Replacing your traditional timing chain with a gear drive delivers more accurate valve timing, increased durability, and a distinctive sound that many gearheads love.

In this article, we will explore what makes a gear drive a worthwhile addition, guide you through the installation process, and offer tips for long-term maintenance and troubleshooting.

Enhancing Engine Performance with a Gear Drive

Upgrading to a gear drive timing set brings several key advantages over a standard timing chain:

• Precision Timing: A gear drive eliminates chain stretch, helping maintain accurate camshaft timing throughout the engine’s life. This improves combustion efficiency, throttle response, and overall engine performance.
• Durability: Gear drives are made from hardened steel and are built to withstand the stresses of high-performance applications. Unlike chains, they do not suffer from wear-induced slack.
• Instant Response: By eliminating chain deflection and stretch, gear drives offer more immediate power transfer from the crankshaft to the camshaft.
• Sound: A gear drive produces a characteristic whine, often compared to a supercharger. While this is cosmetic, it is a sought-after effect in muscle car builds.

Whether you are building a street-driven small block or a weekend drag racer, a Chevy 350 gear drive offers both form and function.

Step-by-Step Installation Guide

Before beginning the installation, confirm the correct part number for your application. This article covers:

• Small Block Chevy (JEGS part numbers 555-20311, 555-20310, 555-20316)

Always rotate the engine to top dead center on cylinder number one before beginning removal of the original components.

1. Remove the Timing Cover

Carefully remove the stock timing cover and rotate the crankshaft so the timing marks on the crank and cam sprockets are aligned. The crank gear mark should be at 12 o'clock and the cam gear at 6 o'clock.

2. Remove the Chain and Sprockets

With the marks aligned, remove the cam and crank sprockets along with the timing chain.

3. Replace Cam Thrust Plate Bolts

For proper clearance, replace the cam thrust plate bolts with the provided button-head Allen bolts. Apply thread locker and torque as needed.

4. Install the Cam Gear

Install the cam gear using the included press-fit thrust bearing. Rotate it by hand to verify it moves freely. Torque cam bolts to the factory specification of 21 ft-lbs using the provided washers.

5. Install the Crank Gear

Slide the crank gear onto the crankshaft, choosing from the three keyway options:

• O mark for standard timing (OEM cam timing)
• Triangle mark for 4 degrees camshaft advance
• Square mark for 4 degrees camshaft retard

Use the keyway that best suits your desired timing.

6. Position the Idler Gears

Install the dog bone idler assembly between the cam and crank gears. Ensure it aligns as shown in your provided instructions.

Note: This gear drive system is designed to fit under factory steel or chrome replacement timing covers. If you are using an aftermarket aluminum timing cover, you may need to adjust clearance between the bearing and the inside of the cover.

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Clearance Testing

Proper clearance is critical to ensure reliable operation and prevent damage to the timing cover or block.

Power Idler to Engine Block Clearance

1. Begin with the idler gears halfway seated in place.
2. Install the timing cover (with gasket) and press it into position.
3. Remove the cover and inspect where the idlers sit.

Use clearance putty to check the distance between the power idler axle and the block. There must be at least 0.005 inches of end clearance. If the axle contacts the block, gently grind the axle end until the minimum clearance is achieved.

Never allow the idler axles to be trapped between the cover and the engine block.

Alternate Clearance Check

Use clearance putty without the gasket installed. Hand-tighten the timing cover and then remove it. A thin film of putty remaining on the axle confirms you will have the correct 0.005 to 0.075 inch clearance once the gasket is in place.

Note: This system must be used with a properly installed harmonic balancer.

Maintenance and Troubleshooting Tips

Maintaining your gear drive timing set ensures long service life and optimal engine performance.

• Use quality oil and change it regularly to keep metal particles and debris from affecting the gear interface.
• Listen for excessive gear noise. While a mild whine is normal, any knocking or grinding may indicate improper clearance or wear.
• Check fasteners during routine service to confirm torque settings have not shifted.
• Avoid excessive RTV or sealant that can squeeze into the gears during timing cover installation.
• Inspect timing cover clearance anytime the cover is removed or replaced.

If your gear drive whine becomes louder than expected, it may be caused by too tight of a fit against the cover or the block. Recheck your clearance using the putty method if you suspect interference.

Final Thoughts

A Chevy 350 gear drive system offers a smart upgrade for anyone seeking improved timing accuracy, performance, and durability. While the installation process requires some attention to detail, the benefits make it a worthwhile investment for street and track builds alike.

If you need help choosing the right gear drive timing set or have questions about installation, reach out to the experts at JEGS. We carry a full line of gear drive systems, harmonic balancers, timing covers, and camshaft components to help you complete your build with confidence.

Visit JEGS.com or call our tech team at 1-800-345-4545 for product support and personalized recommendations.