A Deep Dive into the 1974-1984 Jeep Cherokee SJ Engine Timing Set

Is Your Cherokee's Timing Set Failing?

The timing set on the AMC engines used in the 1974-1984 Cherokee (SJ) is a durable part, but it does wear out. The original timing sets on the AMC V8 engines famously used a camshaft gear with nylon-coated teeth. This was done to make the engine run quieter. However, after decades of heat and mileage, the nylon becomes brittle, cracks, and can break off. These pieces can clog the oil pump pickup screen, leading to oil starvation and major engine damage. The chain also stretches over time. Here are the common symptoms of a worn timing set:

Symptoms of a Bad Timing Set

• Rattling Noise: The most common sign is a rattling or clattering sound coming from the front of the engine, especially noticeable at idle. This is the sound of a stretched timing chain slapping against the inside of the timing cover.
• Inconsistent Ignition Timing: If you try to set the ignition timing with a timing light, you may find the timing marks jump around erratically. A stretched chain causes the camshaft's position to vary, making it impossible to set a stable timing.
• Engine Misfires or Rough Running: As the chain stretches, it can cause the valve timing to become retarded. If it stretches enough, it can jump a tooth on one of the gears, throwing the timing off significantly and causing the engine to run poorly, misfire, or not start at all.
• Metal Shavings in Oil: When changing your oil, finding small metal or plastic shavings in the drained oil or on the magnetic drain plug is a serious warning sign. These could be pieces of the nylon cam gear or metal from the chain itself.

Choosing the Right Aftermarket Timing Set

Since OEM parts are largely unavailable, the aftermarket is your go-to source. For this specific vehicle, aftermarket parts are often an upgrade over the original design, especially for the V8 engines. Here’s a breakdown of your options:

Tier 1: Performance & Heavy-Duty Sets

Brands: COMP Cams, Edelbrock

These brands specialize in high-performance parts. Their timing sets for the AMC engines are a significant upgrade. They typically feature a "double roller" chain, which is much stronger and less prone to stretching than the original silent-type chain. The gears are made from hardened steel or iron. Many of these kits also include a multi-keyway crankshaft sprocket, allowing a mechanic to advance or retard the cam timing for performance tuning. If you are rebuilding your engine or want maximum durability, this is the best choice.

Tier 2: Quality OE-Style Replacements

Brands: Melling, Cloyes

Melling and Cloyes are reputable manufacturers of stock replacement engine components. Their timing sets are an excellent choice for a daily driver or a standard engine repair. 🎬 See this walkthrough on removing the timing set and camshaft. They offer all-metal gears, eliminating the failure-prone nylon teeth of the V8 original. While some of their offerings are standard silent chains, they also have heavy-duty and double roller options. Forum and user reviews sometimes suggest Melling has slightly more consistent quality control on fit and finish compared to budget Cloyes lines, but both are considered reliable choices.

Tier 3: Budget & Jeep-Specialist Brands

Brands: Crown Automotive, Omix-Ada

Crown and Omix-Ada focus specifically on Jeep replacement parts. They are often the most affordable option. However, user reviews on forums suggest that quality can be inconsistent. While some parts are perfectly fine, critical components like a timing set may have fitment issues or be made from lower-quality materials. It is common for the gaskets included in these kits to be of poor quality. If you choose a budget brand, inspect the parts carefully before installation and consider buying a separate, high-quality gasket set.

Frequently Asked Questions (FAQ)