A Guide to Replacing the Engine Timing Set on Your 1981-1983 Plymouth PB150
Understanding the critical timing set upgrade that can save the engine in your classic Plymouth van.
- The original timing set likely uses a failure-prone nylon cam gear; upgrading to an all-metal aftermarket set is critical for engine reliability.
- Symptoms of failure include engine rattle, loss of power, and an unstable timing mark when checked with a timing light.
- Brands like Cloyes and Melling offer excellent standard replacements, while Edelbrock and double-roller sets provide a performance upgrade.
- While doing the job, it is cost-effective to also replace the timing cover seal, water pump, and thermostat.
The Most Common Failure: Original Nylon Timing Gears
If your 1981-1983 Plymouth PB150 still has its original engine, its timing set likely has a major weak point: a camshaft sprocket with nylon-plastic teeth. Manufacturers used these nylon teeth to make engines run quieter. However, after decades of heat and mileage, this nylon becomes brittle and breaks off. These broken plastic pieces fall into the oil pan and can clog the oil pump pickup screen, starving the engine of oil and leading to catastrophic failure. Upgrading to an aftermarket timing set with all-metal gears is one of the most important reliability improvements you can make.
Symptoms of a Failing Timing Set
A worn or failing timing set will give you several warning signs. Ignoring them can leave you stranded or with a ruined engine.
- Engine Rattle: The most common sign is a rattling or scraping sound coming from the front of the engine, especially on startup. This is the sound of the loose chain slapping against the inside of the metal timing cover.
- Poor Engine Performance: As the chain stretches, it retards the camshaft timing. This results in a noticeable loss of power, especially at low RPMs, rough idling, and hesitation.
- Wandering Ignition Timing: If you check the ignition timing with a timing light, a stretched chain will cause the timing mark to jump around erratically instead of holding steady.
- Backfiring: A severely stretched chain can cause the engine to backfire, particularly when you let off the gas.
- Metal or Plastic in Oil: When changing your oil, finding chunks of plastic or metal shavings in the drained oil or on the magnetic drain plug is a critical sign that the timing gear is disintegrating.
Critical Warning for Original Engines
If your engine has high mileage and you don't know if the timing set has ever been replaced, assume it has the original nylon gear. It is not a matter of if it will fail, but when. Proactively replacing it is much cheaper than replacing the entire engine.
Choosing the Right Aftermarket Timing Set
Since original equipment (OEM) parts are largely unavailable for a vehicle of this age, the aftermarket is your only option. Fortunately, aftermarket sets are a significant upgrade. They replace the failure-prone nylon gear with a durable all-metal sprocket.
Brand Tiers for Your PB150
- Standard Replacement (Good): Brands like Cloyes and Melling offer quality standard replacement kits. These are excellent for a daily driver and provide a huge durability boost over the stock setup by using an iron camshaft gear.
- Heavy-Duty / Performance (Better): For added strength, look for "true roller" or double-roller chains from brands like Cloyes, Melling Select Performance, or Edelbrock. These sets reduce friction and stretch even further, making them a great choice for vans that work hard or have performance upgrades. Edelbrock's kits often feature billet steel crank sprockets for maximum durability.
- INA: While a high-quality brand, INA is less common for this specific vintage American application, and finding a compatible kit may be difficult.
Pro Tip: What to Replace With Your Timing Set
Since you'll have the front of the engine disassembled, it's the perfect time to replace other parts. Always install a new timing cover front seal. It's also wise to replace the water pump, thermostat, and any coolant hoses you have to remove. Inspect the harmonic balancer for damage or rubber separation.
Estimated Replacement Costs
The cost to replace the timing set can vary based on the parts you choose and labor rates in your area. The job is moderately difficult and can take a professional mechanic several hours.
| Part or Service | Estimated Cost |
|---|---|
| New Aftermarket Timing Set | $32 - $168 |
| Shop Labor | $400 - $750 |
| Total Estimated Cost | $432 - $918 |
Frequently Asked Questions (FAQ)
Do I really need to replace my timing set if I don't have symptoms?
If your engine is original with over 100,000 miles, it is highly recommended. The failure of the factory nylon gear can happen suddenly and without warning, causing severe engine damage from oil starvation. It is a preventative repair that can save you thousands of dollars.
What's the difference between a standard chain and a "double roller" chain?
A standard or "silent" chain is similar to the original design. A double roller chain is like a heavy-duty bicycle chain with two sets of rollers, making it stronger and more durable. For most stock applications, a standard all-metal replacement is sufficient, but a double roller is a worthwhile upgrade for longevity and performance applications.
Is the Plymouth PB150 engine an "interference" engine?
No, the Chrysler Slant 6 and 5.2L/318 V8 engines from this era are generally considered non-interference designs. This means if the timing chain breaks, the pistons will not crash into the valves. However, a broken chain can still whip around and cause other damage inside the engine, so a failure should still be treated as a serious event.
Can I replace the timing set myself?
This is a moderately difficult job for an experienced DIY mechanic. It requires draining the coolant, removing the radiator, belts, pulleys, water pump, and harmonic balancer just to access the timing cover. Special tools, like a harmonic balancer puller, are required. If you are not comfortable with this level of disassembly, it is best left to a professional.
Technical Specifications
OEM Part Numbers: OEM parts for this model are generally considered obsolete.
The most important specification is upgrading from the original nylon-toothed camshaft sprocket to a full-metal (cast iron or steel) replacement sprocket. Both single-row 'silent' chains and double-roller chains are available.
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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.
- Plymouth PB150:
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- The Most Common Failure: Original Nylon Timing Gears
- Symptoms of a Failing Timing Set
- Critical Warning for Original Engines
- Choosing the Right Aftermarket Timing Set
- Brand Tiers for Your PB150
- Pro Tip: What to Replace With Your Timing Set
- Estimated Replacement Costs
- Frequently Asked Questions (FAQ)
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