1. Replace the original cast iron cylinder heads with aluminum cylinder heads. The original cast iron cylinder heads are not compatible with unleaded fuel and will eventually cause the engine to overheat and fail. Aluminum cylinder heads are designed to dissipate heat more efficiently and are therefore less likely to cause engine damage.
2. Install hardened valve seats. The original valve seats in the 1968 Z-28 engine are made of a soft metal that is not compatible with unleaded fuel. Over time, the unleaded fuel will erode the valve seats and cause the engine to lose compression. Hardened valve seats are made of a more durable material that is resistant to erosion from unleaded fuel.
3. Adjust the ignition timing. The original ignition timing for the 1968 Z-28 engine is not optimal for unleaded fuel. Unleaded fuel burns faster than leaded fuel, so the ignition timing needs to be retarded in order to prevent engine knocking. The ignition timing can be adjusted by turning the distributor housing.
4. Use a lead substitute additive. Lead substitute additives can be added to unleaded fuel in order to replace the lead that was originally present in leaded fuel. Lead substitutes help to prevent engine damage by lubricating the valve seats and preventing them from eroding.
By making these modifications, it is possible to safely run unleaded fuel in a 1968 Z-28.
