I have a 64 340 hp 409 that is falling on its face after 3000 rpm. It idles very nice maybe a little rich. The engine has about 60000 miles on it so with recent events I started to replace some things the last wires were done in 1971 so i replaced cap rotor wires spark plugs and checked dwell which is at 29. The timing is at 6 degrees before tdc at 550 rpm with vaccum advance disconexted and total advanvane of 36 at 4000 rpm. It has the original 4 jet which was just rebuilt as well as the original fuel pump that was rebuilt. What am I missing