Choosing the Right Spark Plugs for Your 1973-1974 Subaru 1400
Get your classic Subaru running smoothly with the correct spark plugs for its vintage engine.
- Choose standard copper-core spark plugs for the best performance in your 1400's carbureted engine.
- Avoid expensive platinum or iridium plugs, as they offer no real benefit and are not suited for the original ignition system.
- Always verify the spark plug gap is set to 0.032 inches before installation using a feeler gauge.
- Replacement is a very easy DIY job that can solve many common running issues like rough idle and poor acceleration.
Symptoms of Failing Spark Plugs
The engine in your 1973-1974 Subaru 1400 will let you know when the spark plugs are worn out. Because it's a simple, carbureted engine, the signs are usually easy to notice. Worn, fouled, or incorrectly gapped plugs can lead to a number of problems.
- Rough Idle: The engine may shake, vibrate, or sound uneven when you are stopped.
- Difficulty Starting: A weak spark makes it harder for the engine to start, especially in cold weather.
- Poor Acceleration: The car may feel sluggish, hesitant, or jerky when you press the gas pedal.
- Engine Misfires: You might feel a stumbling or jerking from the engine while driving. This happens when a cylinder fails to fire correctly.
- Reduced Fuel Economy: Worn plugs cause incomplete combustion, which means the engine uses more fuel.
No Check Engine Light or Codes
Your 1973-1974 Subaru 1400 was built before modern On-Board Diagnostics (OBD-II). It does not have a computer that will store trouble codes or turn on a check engine light for issues like a misfire. You must rely on noticing these physical symptoms to diagnose a problem.
Choosing the Right Aftermarket Spark Plug
For a classic car like the Subaru 1400, original factory parts are no longer available. Aftermarket spark plugs are the standard replacement, and the quality is excellent. The most important decision is choosing the right type of plug for your vintage ignition system.
Brand Tiers & Material Types
The consensus among mechanics and classic Subaru owners is that these simple engines run best on basic, copper-core spark plugs. They were designed for this technology. While modern platinum and iridium plugs are available, they are not necessary and can sometimes cause running issues in older ignition systems.
- Recommended (Standard Copper): Brands like Autolite and Champion offer standard copper plugs that are a great match for the 1400's engine. They provide reliable performance and are very affordable. Copper plugs are excellent conductors of electricity and work perfectly in this type of engine. They should be inspected and changed more frequently, typically every 15,000-20,000 miles.
- Acceptable (Standard Copper): Bosch also produces reliable standard copper plugs that will work well in your 1400. While Bosch is a quality brand, some owners of older Japanese cars report occasional issues with their platinum plugs, so it's safest to stick with their standard copper options.
- Not Recommended (Platinum/Iridium): While Autolite and Bosch offer platinum or double platinum plugs, these are generally not worth the extra cost for your vehicle. The main benefit of these plugs is a longer service life in modern, high-energy ignition systems. Your 1400's engine will not see a performance improvement from them.
Always Check the Gap
Before installing new spark plugs, always check the gap. The recommended spark plug gap for your Subaru 1400 is 0.032 inches (0.8mm). Plugs can be handled roughly during shipping, which can change the gap. Use a feeler gauge or a spark plug gapping tool to make sure it's set correctly.
| Brand/Type | Estimated Price (per plug) | Notes |
|---|---|---|
| Champion (Copper Plus) | $3.68 - $9.00 | A dependable and affordable choice for vintage engines. |
| Autolite (Copper/Platinum) | $3.68 - $7.00 | Good value and performance. Stick with standard copper if possible. |
| Bosch (Standard/Platinum) | $3.97 - $12.36 | A reliable alternative. Standard copper plugs are the safest bet. |
Note: Prices are estimates based on our inventory and can vary.
Frequently Asked Questions (FAQ)
How often should I change the spark plugs on my Subaru 1400?
For standard copper spark plugs, a good interval is to inspect them every 15,000 miles and replace them every 20,000-30,000 miles, or every 2-3 years. Since the job is easy and the parts are inexpensive, changing them regularly is great preventative maintenance.
Can I use more expensive iridium or platinum plugs in my classic Subaru?
It is generally not recommended. The main benefit of iridium and platinum plugs is a very long service life in modern cars. Your 1400's ignition system was designed for copper plugs, which provide excellent performance at a much lower cost.
Is it difficult to replace the spark plugs myself?
No, this is a very easy job for a DIY mechanic. The spark plugs on the flat-four engine are easily accessible on the sides. The job requires only basic hand tools, like a ratchet and a spark plug socket, and can be completed in under an hour.
What happens if I use the wrong spark plug gap?
An incorrect gap can cause problems. If the gap is too small, the spark may be weak, leading to incomplete combustion and fouling. If the gap is too large, the spark may struggle to jump the gap, causing misfires, especially under load.
Are there any recalls for the spark plugs on my Subaru 1400?
No. Searches of the National Highway Traffic Safety Administration (NHTSA) database show no recalls or technical service bulletins (TSBs) related to spark plugs for the 1973-1974 Subaru 1400. Any failures are due to normal age and wear.
Technical Specifications
Recommended Spark Plug Gap: 0.032 in (0.8mm). Recommended Plug Type: Standard Copper Core. Common Aftermarket Part Numbers: Autolite 63, Champion N9YC, Bosch 7905.
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.