* Measurement Inaccuracy: Your 18" x 60" measurement is likely an approximation taken from the existing, potentially damaged, windshield. Accurate measurements are crucial, and a slight error in measurement can lead to a significant difference in the actual size needed. The 20" dimension likely refers to a *specific* measurement point on the replacement glass (perhaps the width at its widest point), not an overall dimension.
* Different Measurement Points: Windshield dimensions aren't usually given as simple length and width. Manufacturers specify dimensions at specific points along the curvature of the glass. Your "18" and "60" might represent measurements taken at points that don't correspond to the manufacturer's specifications. The replacement glass manufacturer uses their own precise measurement system.
* Year and Model Variations: While it's a 1964 Nova, there might be subtle variations in windshield size depending on the trim level (e.g., coupe, sedan) or even minor production changes throughout the year. Double-check your exact Nova model to ensure you have the correct specifications.
* Curvature: Windshields aren't flat; they're curved. The listed dimensions on replacement glass are often related to the installed, curved dimensions, not the approximate flat measurements.
To find the correct replacement:
1. Verify your Nova's exact model and trim level: This is crucial. A parts catalog specific to your car year and model will give you the precise part number.
2. Consult a reputable parts supplier: Contact classic car parts specialists or auto glass suppliers. Provide them with your VIN (Vehicle Identification Number) for the most accurate match. They have access to the correct dimension specifications.
3. Check online databases: Some online databases for classic car parts (like those specific to Chevy Novas) may list the correct windshield part numbers and dimensions.
4. Measure carefully and professionally: If you must measure yourself, find someone experienced with measuring auto glass to avoid errors. Consider measuring multiple points along the curvature to provide a more complete picture.
In short, don't rely solely on your rough measurements. Use the VIN and consult experts in classic car parts to get the correct replacement windshield size. A 2-inch difference is significant for auto glass.
