Essential Spark Plug Guide for the 1967-1968 Glas 3000 GT
Keep your rare Glas V8 running strong with the right set of new spark plugs.
- For the Glas V8, standard copper core spark plugs are the best choice over modern platinum or iridium types.
- Always replace all eight spark plugs as a set to ensure balanced engine performance.
- Check and set the spark plug gap using a feeler gauge before installation.
- Both Autolite and Champion are available, but Autolite has a more consistent reputation among classic car owners for reliable performance.
Symptoms of Failing Spark Plugs
An engine as unique as the Glas V8 deserves to run at its best. If you notice any of these signs, your spark plugs could be the culprit:
- Rough Idle: An inconsistent or shaky feeling when the car is stopped and in gear.
- Hesitation During Acceleration: The car may stumble or lag when you press the gas pedal.
- Engine Misfires: You might feel a jerking or sputtering from the engine, which can sometimes trigger a check engine light in more modern cars, but will just be felt in a classic like the Glas.
- Reduced Fuel Economy: If you're filling up more often than usual, worn plugs might be causing incomplete fuel combustion.
- Difficulty Starting: Fouled or worn plugs can make it hard for the engine to fire up, especially from a cold start.
Choosing the Right Aftermarket Spark Plug
For a vehicle as rare as the 1967-1968 Glas 3000 GT, finding original "OEM" parts from Glas is not possible. The focus is on finding a high-quality, period-appropriate aftermarket equivalent that works well with your car's original ignition system. The ignition systems in 1960s vehicles are not the high-energy systems found in modern cars, and sometimes have trouble with plugs designed for newer vehicles. For this reason, a standard copper core spark plug is almost always the best choice for your Glas V8.
Aftermarket Brand Comparison
| Brand | Reputation for Classic Cars | Price Tier |
|---|---|---|
| Autolite | Generally considered a reliable and cost-effective choice. Many classic car owners have used Autolite copper plugs for decades with good results, noting their dependable performance in older engines. | $ |
| Champion | A historic brand with a long legacy in motorsports. However, some owners of antique vehicles report mixed experiences with modern Champion plugs, occasionally citing issues with fouling or failures right out of the box in older, lower-voltage ignition systems. | $ |
Pro Tip: Stick with Copper
While modern plugs advertise fancy materials like platinum and iridium, these are designed for modern high-energy ignition systems. Your Glas V8's original ignition system was designed for standard copper plugs. Copper plugs provide excellent performance in these applications and are much more affordable, making it easy to change them more frequently to keep your engine in top tune.
Frequently Asked Questions
Should I use modern Iridium or Platinum plugs in my Glas?
It is not recommended. These plugs are designed for modern cars with very different ignition systems. They are more expensive and may not perform well, potentially leading to fouling or misfires in a classic engine. Standard copper core plugs are the best match for your vehicle's original design.
What should the spark plug gap be?
Spark plug gap is critical. While original specs for the Glas V8 are not readily available, aftermarket manufacturers provide a recommended gap for their specific plugs. For example, some cross-references suggest a gap of .025 inches. Always check the manufacturer's recommendation for the specific plug you are buying and use a feeler gauge to verify the gap before installation.
How often should I change the spark plugs?
For a classic car like the Glas 3000 GT using standard copper plugs, a good interval is every 10,000 to 15,000 miles or every 2-3 years, whichever comes first. Because they are inexpensive, frequent changes are an easy way to maintain peak performance and identify any potential engine issues by 'reading' the old plugs.
Do I need to replace all eight spark plugs at once?
Yes. Always replace spark plugs as a complete set of eight. This ensures consistent performance across all cylinders and helps the engine run smoothly. Mixing old and new plugs can cause an imbalance in engine operation.
Technical Specifications
While original Glas specifications are unavailable, modern aftermarket cross-references point to plugs with a 14mm thread, 19mm reach, and a 5/8" hex size. A common gap specification is .025 inches. Example aftermarket part numbers include Autolite APP63 and Champion 9804.
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.