Square-body C/K trucks (1973-1987) shipped with factory evap hardware, but on a 40+ year-old truck the original canister is frequently missing, cracked, or has been removed during an engine swap. The Vapor Trapper is a direct functional replacement.
What your vehicle came with from the factory
All 1973-1987 C/K trucks were sold with a factory charcoal canister and purge plumbing as part of federal evap requirements. Dual-tank trucks (16 + 20 gallon, or 20 + 20 gallon configurations) used a frame-mounted selector valve and ran a single canister to handle vapor from both tanks. The original canisters were plastic-bodied and inner-fender mounted.
What's vehicle-specific to watch for
- Single-tank trucks have a tank vent line that runs forward along the frame rail — typically along the driver's side.
- Dual-tank trucks rely on the existing tank-selector vent routing; bypassing the selector valve is generally not advised because both tanks then vent simultaneously.
- TBI (1987 and a few 1986 variants) and any LS-swap truck will want the canister and purge plumbing functional — the ECU expects to see EVAP activity.
- Inner-fender mounting in the engine bay matches the factory location and keeps the purge line short.
- For very large dual-tank combined capacity (40+ gal), the High Capacity Vapor Trapper is worth considering over the Standard.
Notable years & fun facts
- The "square-body" nickname is enthusiast-coined — Chevrolet officially called these "Rounded-Line" trucks at launch, contrasting them with the prior "Action Line" generation.
- 1973-1987 is the longest single body-style run for a GM pickup, spanning 15 model years with only minor sheetmetal changes.
- The 1982-1987 Suburban had a 40-gallon (16+24) dual-tank option that's still one of the largest factory fuel capacities ever offered in a U.S. consumer SUV.
For the actual installation steps, see the universal Vapor Trapper installation guide — the procedure is the same across vehicles, only the routing and mounting changes.
Building something specific or unsure about routing on your application? Contact us with a few photos of your engine bay and tank area and we'll help you spec the right setup.
VaporCanister.com is an authorized retailer of the Vapor Trapper™ by Shop48.
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