Hi, Just got my 66 Fury III 318 and runs fine except it's rough at idle. Vacuum is normal but shakes or flutters. Compression is good 180pounds per cylinder, just rebuilt the Stromberg 3-261 carb. Still idles rough. Can the compression still show good but the valves be too tight (I haven't checked the valves)? Also, could a loose timing chain cause this? Did they use a nylon sprocket on this engine? Engine has 125k miles on it. Thix!