Choosing the Right Engine Timing Set for Your 1969-1975 Chevrolet Blazer
Keep your classic Blazer's engine running strong and reliable with a durable new timing set.
- Upgrade from the original nylon-toothed cam gear to an all-metal aftermarket set for significantly improved durability.
- For most stock engines, a standard replacement set from a reputable brand like Melling or Cloyes is an excellent and affordable choice.
- This is a labor-intensive job; plan to also replace the timing cover gasket, front crankshaft seal, and water pump while the area is accessible.
- Verify your specific engine (e.g., 250 I6, 350 V8) before ordering to ensure you get the correct part.
Is Your Blazer's Timing Set Failing?
The first-generation Chevrolet Blazer, particularly those with V8 engines like the 307 and 350, often used a camshaft gear with nylon-coated teeth. This was done to reduce engine noise. After decades of heat cycles and exposure to engine oil, this nylon becomes brittle. It's a common point of failure for these classic engines. When the nylon teeth break off, they can clog the oil pump pickup screen, starving the engine of oil. The chain itself can also stretch, causing timing to become inaccurate. Listen for a rattling sound from the front of the engine, especially at idle or on startup, as this is a classic sign of a loose timing chain slapping against the timing cover.
The Nylon Gear Problem
If your engine is original, it likely has a cam gear with nylon teeth. This is not a question of if it will fail, but when. When replacing your timing set, it is crucial to upgrade to a full-metal gear set for long-term reliability. The slight increase in engine noise is a small price to pay for durability and peace of mind.
Choosing the Right Aftermarket Timing Set
For a vehicle of this vintage, high-quality aftermarket parts are often superior to the original factory components. You have several excellent options depending on your needs and budget. It is always recommended to replace the timing components as a set—chain, camshaft gear, and crankshaft gear—as they are designed to wear together.
| Brand Tier | Brands | Best For | Key Features |
|---|---|---|---|
| Standard Replacement | Cloyes, Melling, INA | Stock or daily-driven Blazers. | Meets or exceeds original specifications. All-metal gears provide a significant durability upgrade over original nylon-toothed gears. Excellent value. |
| Performance / Heavy-Duty | Melling Select Performance, Edelbrock, Cloyes (Performance Series) | Modified engines, towing, or heavy off-road use. | Often feature double-roller chains for increased strength and reduced stretch. Some sets offer multiple keyways on the crank sprocket for advancing or retarding cam timing. |
Pro Tip: While You're In There...
Replacing the timing set is a labor-intensive job that requires removing the water pump, harmonic balancer, and timing cover. This is the perfect time to replace the timing cover gasket, front crankshaft seal, and water pump gaskets to prevent future leaks. Consider replacing the water pump itself if its age is unknown.
Frequently Asked Questions (FAQ)
Do I need a special "double-roller" timing chain?
For a stock or mildly modified engine, a standard single-roller, all-metal set from a quality brand like Melling or Cloyes is more than adequate and a huge upgrade over the original. Double-roller chains are stronger and are great for high-RPM, high-performance engines, but they are not a necessity for most classic Blazers.
Are there any recalls or TSBs for my Blazer's timing set?
Due to the age of the 1969-1975 Blazer, there are no active recalls or Technical Service Bulletins (TSBs) on file with the NHTSA for timing set issues. The common failure of the nylon cam gear is a well-documented issue within the owner and mechanic community, but it was never subject to an official recall.
Can I replace just the chain?
No. The chain and sprockets wear together as a matched set. Installing a new chain on old, worn sprockets will cause the new chain to wear out very quickly and can lead to inaccurate timing. Always replace the chain and both sprockets as a complete kit.
What is the most common mistake when ordering this part?
The most common mistake is ordering a timing set for the wrong engine. The 1969-1975 Blazer was available with several engines, including the 250 inline-6, 307 V8, and 350 V8. These engines use different timing sets. Always verify your Blazer's specific engine before ordering parts.
Technical Specifications
Compatibility is based on the specific engine in your 1969-1975 Blazer (e.g., 250ci I6, 307ci V8, 350ci V8). Standard replacement sets typically feature a cast iron cam sprocket and a steel crank sprocket. Performance sets may use billet steel and feature a double-roller chain. Always confirm fitment for your specific engine.
We Have This Part in Stock
The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.