Engines that are relatively straightforward swaps (often requiring some adaptation but less extensive fabrication):
* Buick V8s from the same era (late 60s-early 70s): This is the easiest route. Engines like the 400, 425, and 455 cubic inch Buick V8s are common swaps and often utilize existing mounting points with minimal modification. Finding the right transmission (likely a TH400 automatic or a manual) that fits those engines is relatively easier too.
* Chevy big-block V8s (e.g., 454): These are popular swaps in many classic cars, but require more fabrication work to fit into the Riviera's engine bay. Custom motor mounts and potentially other modifications will be necessary.
* Other GM big-block V8s (e.g., Oldsmobile 455): Similar to the Chevy big-blocks, these require more fabrication than Buick V8s but are a relatively common swap in classic cars.
Engines that are significantly more challenging or impractical:
* Small-block Chevy V8s: Though seemingly simpler, they might require more custom fabrication to get the proper fit and balance.
* Modern fuel-injected V8s (LS series, Coyote, etc.): These are increasingly popular in custom builds, but will require significant fabrication and modification to the engine bay, wiring, and potentially the entire drivetrain.
* Any engine significantly larger or wider than the original 425: These will present major challenges fitting into the engine bay and may require significant bodywork.
* Inline-6 or 4-cylinder engines: While possible, these aren't common swaps and would require substantial custom fabrication.
Crucial Considerations:
* Transmission: The transmission choice is just as important as the engine. You need to find one that fits the engine and the Riviera's existing drivetrain components (driveshaft, rear end).
* Wiring: Adapting the electrical system to the new engine is often a significant undertaking.
* Cooling System: Making sure the engine is adequately cooled is vital, especially with larger or higher-performance engines.
* Exhaust System: A custom exhaust system is virtually always necessary.
In short, while numerous engines *could* fit, the practical choices heavily favor similar-sized GM big-block V8s from the same era. Anything outside that range requires significant mechanical and fabrication skills and a substantial investment of time and money. Always research specific engine-swap builds for the '67 Riviera to see what others have successfully done and the challenges they faced.
