My '67 4.2 liter E-Type lives at 9100 feet. The engine runs strong and smooth until about 2800 RPM and then it starts missing, sputtering and stumbling. It will continue to accelerate, but more slowly and with a very rough engine response.
My mechanic and I have checked out a number of potential problems, and none has worked. We have checked and rechecked the timing, adjusted the carbs a thousand ways, cleaned fuel filter and checked fuel pump. We have installed Pertronic ignition--no help.
The carbs have not been rejetted, but my mechanic has said he has never had to do that before for various XK engines at this altitude. The plugs are new and are not fouled or too light. It also seems strange that the engine is so strong and sweet below 2800 RPM.
Ideas?
Dan