A buddy of mine has a 1955 Thunderbird and claims it's a 312 Y-block (which from what I find can't be the original engine) that's freshly rebuilt and fully restored with only 13 miles on it. He claims not to drive it because the engine shakes. Unfortunately he wasn't about to start it as the battery was completely done after sitting for a year. My question is, are these internally balanced? If they are is the only remedy to rebuild and re-balance the rotating assembly?
Thanks.
Thanks.