Ignition Contact Set Guide for the 1947 GMC EC250
Everything you need to know about replacing the ignition points in your classic GMC truck.
- The ignition contact set (points) is a normal wear item on a 1947 GMC EC250 and requires periodic replacement.
- Since new OEM parts are unavailable, a quality aftermarket brand like Standard Ignition is the recommended choice.
- Symptoms of failure include hard starting, rough idle, misfires, and power loss.
- Proper installation, including setting the correct point gap (typically .019" for new points), is critical for engine performance.
Understanding the Ignition System in Your Vintage GMC
For owners of a 1947 GMC EC250, the ignition system is a far cry from modern electronic setups. It relies on a mechanical system where the ignition contact set, or points, are a primary wear item. These points are a simple switch that opens and closes thousands of times per minute. Over time, the electrical arcing and mechanical friction cause the contact surfaces to pit and the rubbing block to wear down, requiring regular service and eventual replacement.
Symptoms of Failing Ignition Points
When the ignition contact set begins to fail, it can cause a range of engine performance issues. Recognizing these signs can help you diagnose the problem before you're left stranded.
- Hard Starting or No Start: Worn or corroded points can't make a clean electrical connection, leading to a weak or nonexistent spark.
- Rough Idle and Stalling: If the points are pitted or the gap is incorrect, the engine timing can become erratic, causing the engine to run poorly at low speeds or stall.
- Engine Misfires: Especially under load or at higher RPMs, worn points can "bounce" or fail to open and close cleanly, resulting in misfires and a loss of power.
- Backfiring: Incorrect timing from faulty points can cause the engine to backfire through the carburetor or exhaust.
No Recalls or Technical Service Bulletins Found
A search of the National Highway Traffic Safety Administration (NHTSA) database and other sources did not reveal any specific recalls or technical service bulletins (TSBs) for the ignition contact set on the 1947 GMC EC250. Given the vehicle's age, issues are typically addressed through standard maintenance and repair procedures.
Choosing the Right Aftermarket Ignition Contact Set
For a vehicle from 1947, new original equipment (OEM) parts from GMC are no longer produced. Your only option is new aftermarket parts or, if you can find them, New Old Stock (NOS) parts. Fortunately, the aftermarket provides reliable replacements.
Standard Ignition: This brand is a well-regarded choice in the classic car community for ignition components. Forum discussions among vintage vehicle owners often mention Standard Ignition and its premium "Blue Streak" line as being a quality option for points and condensers. For a component as critical and inexpensive as points, choosing a reputable brand like Standard Ignition is a wise investment in your truck's reliability.
| Part Type | Brand | Price Range |
|---|---|---|
| Ignition Contact Set | Standard Ignition | $21.44 |
Pro Tip: Replace the Condenser Too
The condenser is a small capacitor that works with the points to prevent excessive arcing. A failing condenser can cause the new points to burn out very quickly. Since condensers are inexpensive and new ones are typically included with a quality set of points, you should always replace the condenser at the same time as the points.
Frequently Asked Questions
What are ignition "points"?
"Points" is the common name for the ignition contact set. It's a mechanical switch inside the distributor that triggers the spark from the ignition coil. This system was used in most vehicles before the widespread adoption of electronic ignition in the 1970s.
How often should I replace my ignition points?
As a general maintenance item, ignition points should be inspected at every tune-up. They typically require replacement every 10,000 to 12,000 miles, as the rubbing block wears and the contacts erode.
What is the correct point gap for my 1947 GMC truck?
The point gap is a critical adjustment. While specific data for the EC250 is scarce, similar 6-cylinder GM truck engines of the era typically require a gap of .019 inches for a new set of points. This is measured with a feeler gauge when the points' rubbing block is on the highest point of the distributor cam lobe.
Can I upgrade to electronic ignition?
Yes, many owners of classic trucks choose to convert from a points-based system to an electronic ignition. These kits eliminate the need for regular points replacement and can offer more consistent performance. However, a properly maintained set of quality points is very effective and keeps the truck in its original configuration.
Technical Specifications
Point Gap (New): .019 inches (typical for similar GM 6-cylinder engines)
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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.