Here are the best places to search:
* Online Repair Manuals: Sites like Haynes.com or ChiltonDIY.com often sell downloadable repair manuals. These manuals usually include detailed vacuum diagrams. Search specifically for a manual for your 1987 Chevy Nova and *specify the engine size*.
* Auto Parts Store Websites: Websites of major auto parts stores (like AutoZone, Advance Auto Parts, NAPA) sometimes have free diagrams available for download. Again, you'll need to specify your Nova's engine. Their online parts search usually requires the VIN.
* eBay or Online Forums: You might find someone selling a scanned copy of a relevant page from a repair manual on eBay or in forums dedicated to Chevy Novas or classic cars.
* Local Mechanic: A local mechanic familiar with older GM vehicles might have access to a service manual or be able to provide the diagram.
Crucial Information: To get the correct diagram, you *absolutely need* to know the engine size and possibly the VIN (Vehicle Identification Number) of your 1987 Chevy Nova. This information is critical for accurate results. The VIN is usually found on the driver's side dashboard, near the windshield.