I have had my '65 Mustang for years and have never had this kind of trouble. It was running great, but now is only running on four cylinders (1,2,3,&6). I have replaced spark plugs, wires, points, rotor and dist. cap. The timing could be off, but there is no smoke in the exhaust. While the engine is running I tried removing plug wires from plugs 4 and 5. There was no change in engine sound. I would appreciate any tips you may have.

 

buy a 289, you can find one for 100 bucks

 

Ha! Ha! I'd like to keep it original.

 

im not really sure what could be wrong with it. It could be messed up valves or bad compression. I would check the compression first and if its low it is probably the valves.