Spark Plug Guide for the 1938 Chrysler C19 Imperial
Keep your classic Chrysler's straight-eight engine firing reliably with the correct spark plugs.
- Use standard copper-core spark plugs like the Champion J8C, which was a period-correct type for this engine.
- Avoid modern platinum or iridium plugs, as they are not compatible with the C19's original ignition system.
- Always check and set the spark plug gap to approximately 0.030 inches before installation.
- Replacing spark plugs is a simple and inexpensive maintenance task you can do yourself in under an hour.
Signs of Failing Spark Plugs
Worn or fouled spark plugs can cause noticeable running issues in your Chrysler C19. Because these classic engines are mechanically simple, a change in performance often points to a basic ignition tune-up item like the plugs. If your spark plugs are failing, you will likely notice one or more of the following symptoms:
- Rough Idle: The engine may shake or run unevenly when the car is stopped.
- Engine Misfires: You might feel a stumble or hesitation from the engine, especially when accelerating. A popping sound from the exhaust can also indicate a misfire.
- Hard Starting: Weak spark makes it difficult for the engine to fire up, especially when cold.
- Reduced Power and Fuel Economy: Incomplete combustion in the cylinders means you are not getting the full power from your fuel, leading to sluggish performance and more trips to the gas station.
- Fouled Plugs: When you remove the plugs, they may appear black and sooty or oily. This indicates a problem with the fuel mixture, oil consumption, or the plug's heat range.
Choosing the Right Aftermarket Spark Plug
For a vintage vehicle like the 1938 C19, the line between "OEM" and "aftermarket" is blurry. Brands that were original equipment in the 1930s are now sold as aftermarket parts. The key is to choose a plug with the correct specifications, not necessarily a modern, high-tech one.
Brand Recommendations
| Tier | Brand | Assessment |
|---|---|---|
| Tier 1 (Period-Correct) | Champion | Champion was a primary original equipment supplier for Chrysler in this era. Using a Champion J8C or an equivalent copper plug is a reliable choice that maintains originality and performance. These plugs are designed for the C19's ignition system and provide dependable service. |
| Tier 2 (Functional Alternative) | Motorcraft | Motorcraft, a Ford-associated brand, offers plugs that can cross-reference to the correct Champion specification (such as the Motorcraft A7). While not original to a Chrysler, they are a functional and quality alternative if Champion plugs are not available. The most important factor is matching the heat range and thread specifications. |
Pro Tip: Stick with Copper Plugs
Avoid the temptation to use modern platinum or iridium spark plugs in your C19. The ignition system on this classic vehicle was not designed for the electrical requirements of these newer plug types. Standard copper-core plugs provide the best performance and reliability for your straight-eight engine.
Known Issues, Recalls, or TSBs
Due to the age of the 1938 Chrysler C19, there are no official recalls or Technical Service Bulletins (TSBs) from the NHTSA regarding spark plugs. Any running issues are typically related to normal wear and tear of ignition components. Owners on classic car forums, such as the Antique Automobile Club of America, frequently recommend standard Champion or Autolite plugs and emphasize setting the correct gap for smooth operation.
Cost of New Aftermarket Spark Plugs (1938 Chrysler C19)
| Part Type | Price Range (Per Plug) |
|---|---|
| New Aftermarket (Champion, Motorcraft) | $3.70 - $7.10 |
Note: Your C19 requires eight spark plugs. Prices are estimates and may vary based on the supplier and brand.
Frequently Asked Questions (FAQ)
What is the correct spark plug for a 1938 Chrysler C19?
The most commonly recommended and period-correct spark plug is the Champion J8C or a direct cross-reference like the NGK B6S. Always confirm the 14mm thread size and 3/8" reach.
What is the correct spark plug gap?
The recommended spark plug gap is typically 0.030 inches for this engine. Always verify with a feeler gauge and adjust the new plugs before installation, as they may not be pre-gapped correctly for your specific vehicle.
How often should I change the spark plugs?
For a classic car with a vintage ignition system and standard copper plugs, a good interval is every 10,000 to 15,000 miles or every few years, depending on usage. Given the low cost, it's an easy piece of preventative maintenance to keep the engine running smoothly.
Do I need special tools to change the spark plugs?
No, the job is straightforward. You will need a standard spark plug socket (typically 13/16" or 21mm hex size), a ratchet, and a spark plug gap gauge. Access to the plugs on the straight-eight engine is generally very good.
Technical Specifications
OEM Part Numbers: Champion J8 Champion J8C
Thread Size: 14mm, Reach: 0.375 in (9.5mm), Hex Size: 13/16 in (21mm), Seat Type: Flat Gasket, Recommended Gap: 0.030 in.
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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.