1. Engine Selection and Acquisition:
* Compatibility: You'll need to find a 6-cylinder that physically fits the Comanche's engine bay. AMC (American Motors Corporation), which built the Comanche, offered several inline-6 engines. A common swap candidate is the AMC 232 or 258 inline-6, due to their availability and relative ease of fitting. Other engines might require significant modifications.
* Condition: Acquire a running engine in good condition. A rebuild might be needed depending on the condition of the used engine.
* Completeness: Ensure you get all necessary components: engine block, heads, intake manifold, carburetor or fuel injection system, alternator, starter, etc.
2. Mechanical Modifications:
* Engine Mounts: The 4-cylinder's engine mounts won't work. You'll need new engine mounts specifically designed for a 6-cylinder in a Comanche, either custom-fabricated or sourced from a company specializing in Jeep swaps.
* Transmission: The existing transmission may not be strong enough or may not have the correct bolt pattern to mate with the 6-cylinder. You might need a different transmission, and that brings its own set of challenges (adapter plates, driveshafts, etc.).
* Driveshaft: The driveshaft length will likely be wrong for the new engine and transmission combination. You'll likely need a custom driveshaft or a shortened one.
* Exhaust System: The existing exhaust system won't fit. You'll need a custom exhaust system built or find an aftermarket system designed for the chosen 6-cylinder engine.
* Cooling System: The existing radiator and cooling system might not be sufficient for the larger 6-cylinder engine. Upgrade might be necessary.
* Wiring Harness: The electrical system will need to be adapted to accommodate the 6-cylinder's electrical needs. This may involve modifying the existing harness or using a custom harness. Expect some rewiring.
* Fuel System: You might need to upgrade the fuel pump, lines, and potentially the fuel tank to handle the increased fuel demand of the larger engine.
* Brakes: Consider upgrading the braking system, as a more powerful engine requires improved stopping power.
3. Other Considerations:
* Body Modifications: You might need to do some minor bodywork to accommodate the larger engine, especially around the firewall and under the hood.
* Inspection and Legal Compliance: Ensure your modifications comply with local regulations and pass any necessary vehicle inspections.
* Cost: The cost of parts, labor, and potential unforeseen issues can add up significantly. Budget accordingly.
* Skills and Tools: This is a project that requires mechanical aptitude, welding skills (potentially), and a good set of tools. Unless you're experienced, consider seeking professional help.
In short: This is a challenging project even for experienced mechanics. It's not a simple bolt-on swap. Research specific engine choices and consult forums and communities dedicated to Jeep Comanche modifications for detailed information and potential pitfalls before embarking on this project. Expect to spend significant time, money, and effort.
