Guide to Spark Plugs for the 1956 Nash Ambassador Special
Keep your classic 1956 Ambassador running strong by understanding and choosing the right spark plugs for its specific engine.
- Stick with standard copper-core spark plugs from a brand like Champion; they are correct for your Ambassador's original ignition system.
- Always verify the spark plug gap before installation. The correct gap is 0.030" for the 6-cylinder and 0.035" for V8 models.
- Symptoms like rough idle, poor acceleration, and hard starting are strong indicators that it's time to inspect or replace your spark plugs.
- Replacing spark plugs is a simple, inexpensive DIY maintenance task that can significantly improve engine performance.
Symptoms of Failing Spark Plugs
When spark plugs get old and worn, they can't create a strong enough spark. This leads to several noticeable problems. Since your 1956 Ambassador doesn't have modern warning lights, you'll need to pay attention to how the car sounds and feels.
- Rough Idle: The engine may sound shaky or uneven when the car is stopped, and you might feel more vibration than usual.
- Engine Misfires: You may feel the engine hesitate, jerk, or stumble, especially when you are accelerating. This happens when a cylinder doesn't fire correctly.
- Poor Acceleration: If your Ambassador feels sluggish or slow to respond when you press the gas pedal, a weak spark could be the cause.
- Reduced Fuel Economy: A sudden drop in your gas mileage can be a sign that your plugs aren't burning fuel efficiently.
- Difficulty Starting: Worn-out spark plugs make it harder for the engine to start, particularly in cold weather.
Choosing the Right Aftermarket Spark Plug
For a classic vehicle like the 1956 Nash Ambassador, selecting the right spark plug is simple. The original ignition systems were designed for standard copper-core spark plugs. Fancy, expensive plugs like platinum or iridium are not necessary and won't provide any benefit to your car's vintage ignition system.
Champion was a common original equipment brand for cars of this era and remains an excellent choice today. Sticking with a standard copper plug from a reputable brand is the best way to ensure reliable performance.
Pro Tip: Check the Spark Plug Gap!
New spark plugs are not always pre-gapped correctly for your specific engine. An incorrect gap is a common cause of poor performance. Always use a feeler gauge or a gapping tool to check and set the gap before installation. The correct gap depends on which engine your Ambassador has.
Cost for Aftermarket Spark Plugs
Spark plugs are an inexpensive but critical maintenance item. You will need one spark plug for each cylinder in your engine—six for an inline-6 and eight for a V8.
| Part | Price Range (Per Plug) |
|---|---|
| New Aftermarket Spark Plug | $3.50 - $9.31 |
Known Issues, Recalls, or TSBs
There are no active recalls or Technical Service Bulletins (TSBs) from the National Highway Traffic Safety Administration (NHTSA) for spark plugs on the 1956 Nash Ambassador Special. This is expected for a vehicle of this age, as the NHTSA was not established until 1970.
Frequently Asked Questions (FAQ)
How often should I change the spark plugs on my Nash Ambassador?
For a classic car with a standard ignition system using copper plugs, it's a good practice to inspect them annually and replace them every 10,000 to 15,000 miles. Given their low cost, changing them every few years regardless of mileage is cheap insurance for a healthy engine.
What is the correct spark plug gap for my 1956 Ambassador?
The gap is critical and depends on your engine. For the 6-cylinder engine, the gap is 0.030". For the V8 models (both the Packard-built 352ci and the AMC 250ci), the correct gap is 0.035".
Should I use modern platinum or iridium spark plugs?
No. The ignition system in your 1956 Ambassador was designed for standard copper-core spark plugs. Modern plugs with precious metals will not improve performance and may even cause a weaker spark in a vintage ignition system. Stick with the basics.
What do fouled spark plugs look like?
A fouled plug is covered in a substance that prevents it from sparking correctly. A black, sooty deposit can indicate a fuel mixture that is too rich. An oily, wet deposit can point to more serious internal engine problems, such as worn piston rings allowing oil into the combustion chamber.
Technical Specifications
Engine Options for 1956: 252.6ci I6, 250ci V8, 352ci V8. Spark Plug Gap (6-Cylinder): 0.030 inches. Spark Plug Gap (V8): 0.035 inches. Electrical System: 12-Volt.
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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.