A Mechanic's Guide to the Ignition Contact Set for 1947-1949 GMC 150-22
Keep your classic GMC's engine firing correctly by understanding its ignition points.
- Failing ignition points will cause your truck to run poorly, stall, or not start at all.
- For this classic truck, new OEM parts are not available; a quality aftermarket brand like Standard Ignition is a reliable choice.
- Always replace the condenser with the points and ensure the gap is set correctly with a feeler gauge.
- This is a low-cost, essential DIY maintenance item for any 1947-1949 GMC 150-22 owner.
Understanding the Ignition System in Your Classic GMC
For owners of a 1947-1949 GMC 150-22, the ignition contact set is a key part of what makes the engine run. Unlike modern cars with fully electronic ignitions, your truck uses this simple, effective mechanical system. The points are a normal wear item, like brake pads or tires. They require periodic inspection, adjustment, and replacement to keep your truck reliable. Over time, the electrical arcing and mechanical rubbing wears them down, leading to a range of engine performance problems.
Symptoms of Failing Ignition Points
When ignition points start to fail, the symptoms are usually noticeable. Catching them early can prevent you from being stranded.
- Difficulty Starting or No Start: Worn, pitted, or burned points can't make proper electrical contact. This results in a weak spark or no spark at all, making the engine hard to start or preventing it from starting entirely.
- Engine Misfires and Rough Running: Dirty or improperly gapped points cause an inconsistent spark. You'll feel this as a rough or shaky idle, and the engine may stutter or hesitate during acceleration.
- Stalling: Failing points often struggle to deliver a consistent spark at low engine speeds. This can cause your truck to stall when you come to a stop or at idle.
- Reduced Power and Acceleration: A weak or intermittent spark leads to inefficient fuel combustion. Your engine won't produce its full power, making the truck feel sluggish.
Pro Tip: Check for Distributor Shaft Wear
When replacing your points, check for side-to-side play in the distributor shaft. A worn bushing can cause the shaft to wobble, making it impossible to set the point gap correctly and leading to a persistent rough run. If there's significant play, the distributor may need to be rebuilt or replaced for a reliable repair.
Choosing the Right Aftermarket Ignition Set
For a vehicle from the 1940s, new Original Equipment Manufacturer (OEM) parts are generally no longer produced. The most practical and common choice is a new aftermarket part. Fortunately, the aftermarket has a long history of supporting these ignition systems.
Standard Ignition: Standard Motor Products (SMP) is a well-known and respected manufacturer of ignition components for American vehicles. They have been making parts for decades and are considered a reliable source for quality aftermarket components, especially when OEM parts are no longer an option. For a critical component like ignition points, using a part from a reputable brand like Standard Ignition ensures better materials and manufacturing, leading to longer life and more reliable performance.
Cost of Replacing an Ignition Contact Set
| Part Type | Price Range |
|---|---|
| New Aftermarket (Standard Ignition) | $21.44 |
| New OEM | Not Available |
| Shop Labor | $50 - $100 |
Frequently Asked Questions (FAQ)
How often should I replace my ignition points?
As a general rule, ignition points should be inspected at every oil change and replaced as part of a tune-up every 10,000 to 12,000 miles. However, if you notice any of the failure symptoms, you should check them immediately.
Is replacing the ignition contact set a DIY job?
Yes, this is a very common DIY job for owners of classic vehicles. It requires basic hand tools, a feeler gauge to set the gap, and sometimes a dwell meter for fine-tuning. It is considered a fundamental tune-up task for these older ignition systems.
Should I replace the condenser at the same time?
Yes, it is highly recommended to replace the condenser whenever you replace the points. The condenser helps prevent the points from arcing and burning out prematurely. Most ignition contact sets are sold with a new condenser for this reason.
Should I upgrade to an electronic ignition?
Many owners of classic trucks choose to convert to an electronic ignition system. These kits replace the points and condenser with a solid-state module, eliminating the need for periodic adjustment. While points are very reliable when maintained, an electronic system offers a 'set-it-and-forget-it' solution that can provide a more consistent spark. This is a matter of personal preference between maintaining originality and reducing maintenance.
Technical Specifications
The most critical specification for installation is the point gap. This is set with a feeler gauge and is essential for correct ignition timing and dwell angle. Always refer to the vehicle's service manual for the exact gap specification.
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.