Here's how to verify:
1. Casting Number: This is the most reliable method. The distributor body will have a casting number stamped or cast into it. This number will often (but not always) indicate the distributor's year, type (HEI, points, etc.), and application. You'll need a parts catalog or online database (like a GM parts website) to look up the casting number and verify its compatibility with your specific 350 engine.
2. Mechanical Advance vs. Vacuum Advance: Inspect the distributor's mechanism. Does it have a vacuum advance canister on the side? This canister provides additional spark advance under load. Most HEI distributors have a built-in centrifugal advance and sometimes vacuum advance. Older points distributors rely solely on mechanical advance and may or may not include vacuum advance. Check your engine's specifications to ensure the distributor's advance mechanisms match.
3. Distributor Shaft: The distributor shaft has a specific diameter and length. Verify this with the shaft of a known-good distributor for your engine or with specifications from a parts catalog. An incorrect shaft can lead to incorrect ignition timing.
4. Distributor Cap: The number of terminals on the distributor cap should correspond to the number of cylinders in your engine (8 for a 350). The rotor should point to the correct cylinder at the number 1 position when the engine is at top dead center (TDC) on the compression stroke of cylinder 1.
5. Ignition Coil: The distributor interacts closely with the ignition coil. Make sure the coil is compatible with your distributor type (e.g., points distributors need a specific type of coil).
6. Year and Model of the Engine/Vehicle: While not always definitive, knowing the year and model of your vehicle or the engine's casting number helps narrow down the possible distributor types. This information can help in cross-referencing parts catalogs and online databases.
7. Visual Inspection: Compare the distributor to photos or diagrams of known-correct distributors for your engine. Pay attention to the overall size, shape, and location of components.
Important Note: If you are unsure, consulting a reputable automotive parts store or a professional mechanic is highly recommended. Incorrect distributor installation can cause serious engine damage. Providing them with your engine's casting number and vehicle information will allow them to provide the correct part.
