Engine Timing Set Replacement Guide for the 1975-1980 Plymouth PB100
Keep your PB100's Slant-6 or V8 engine running reliably by understanding when and how to replace your engine timing set.
- The original nylon cam gear is a common failure point; upgrading to an all-metal aftermarket set from a brand like Cloyes or Melling is essential for reliability.
- A rattling noise from the front of the engine on startup is the most common symptom of a worn timing chain.
- This job is DIY-feasible for an experienced mechanic but requires a special harmonic balancer puller.
- Always verify your engine (Slant-6 or V8) before ordering, as the parts are not interchangeable.
Is Your PB100's Timing Chain on its Last Legs?
The original timing sets on many 1970s Chrysler engines, including those in your PB100, used a camshaft gear with nylon-coated teeth. This was done to keep the engine quiet, but after decades of heat and use, the nylon becomes brittle and can break off. This causes the timing chain to become very loose, leading to a range of engine problems. All-metal aftermarket replacements are a significant and necessary upgrade.
Key Failure Symptoms
- Rattling Noise from the Front of the Engine: This is the most common sign. You may hear a metallic rattling or slapping sound when the engine is first started cold. This is the sound of the loose timing chain slapping against the inside of the timing cover.
- Engine Misfires and Rough Idle: As the chain stretches, your ignition and valve timing can become inaccurate. This can cause the engine to run rough, shake at idle, or misfire during acceleration.
- Loss of Power and Poor Fuel Economy: When the camshaft and crankshaft are not perfectly synchronized, engine efficiency drops. Your van may feel sluggish and you'll notice you're filling up the gas tank more often.
- Metal Shavings in the Oil: When the nylon teeth break off or if you have a metal gear that is wearing excessively, small pieces can end up in the oil pan. If you see metallic or plastic debris during an oil change, it's a serious warning sign.
Critical Failure Warning
If a timing chain becomes too loose, it can jump a tooth on the gears. This will cause the engine to run very poorly or not start at all. In a worst-case scenario, the chain can break, which will cause the engine to stop immediately and may result in severe internal engine damage.
Choosing the Right Aftermarket Timing Set
Since original Mopar parts for this component are no longer available, you will be choosing from aftermarket brands. For a classic workhorse like the PB100, a quality aftermarket set is not just a replacement; it's an upgrade over the original nylon-toothed design.
| Brand Tier | Brands | Quality & Performance Notes |
|---|---|---|
| Standard Replacement (Good) | INA, Melling | These brands are known for providing reliable, OEM-quality parts. A standard all-metal set from Melling or INA is an excellent, durable replacement for a daily-driven or stock PB100. They offer a significant durability increase over the original factory gear. |
| Heavy-Duty / Performance (Better) | Cloyes, Melling Select Performance | Cloyes is a highly respected name in timing components, especially for classic American engines. Their 'True Roller' chains and billet steel gears offer less stretch and more precise timing. These are a great choice if you use your van for heavy hauling or have a mildly modified engine. |
| High-Performance (Best) | Edelbrock | Edelbrock is a top name in performance parts. Their timing sets are often double-roller designs made for high-RPM use and modified engines. While excellent quality, this may be overkill for a stock Slant-6 or 318, but it is a top-tier option for maximum durability. |
Pro Tip: Double-Check Your Engine
The Plymouth PB100 was available with a Slant-6 (225 cid) or a V8 (318 or 360 cid). Timing sets are engine-specific. Always confirm your engine size before ordering to ensure you get the correct part.
Frequently Asked Questions (FAQ)
Do I really need to replace my timing set if I don't have symptoms?
If your engine has high mileage (over 100,000 miles) and is still running on the original timing set, it's wise to replace it as a preventive measure. The original nylon cam gear is a known failure point and it's better to replace it on your own terms than to deal with a breakdown on the road.
Should I get a standard chain or a double roller?
For a stock engine used for normal driving, a quality standard or 'silent' type all-metal chain set is perfectly adequate and a huge upgrade over stock. A double roller chain offers extra strength and accuracy, which is beneficial for performance or heavy-duty applications.
Do I need any special tools for the replacement?
Yes. The most important special tool is a harmonic balancer puller. You will need this to remove the main pulley from the crankshaft before you can access the timing cover. Do not try to pry or hammer the balancer off, as this can cause serious damage.
Is it necessary to replace the water pump at the same time?
While not strictly required, it is highly recommended. The replacement process requires removing many of the same components needed to access the water pump. Replacing the water pump at the same time is cost-effective and can save you from having to do a similar job again in the near future.
Technical Specifications
Kit typically includes one camshaft sprocket, one crankshaft sprocket, and one timing chain. Verify fitment for your specific engine (225 Slant-6, 318 V8, or 360 V8).
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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.