ROTW

It runs smooth at idle, stock low HP cam, no engine miss. It really feels MUCH stronger than a part of the exhaust touching the structure, the aftermarket auto trans shifter feels like a tuning fork.

Hello all. I am thinking of buying a SBC/TH350 260Z (looks like JTR mounts) and drove it last night. It is a typical project car that has had a few owners "helping" along the way and the history is unknown. The current owner got it non-running from a body shop owner who painted it but did not drive it. The current guy mechanical minded enough to figure out that the ditributor was installed incorrectly and get it running, but not too much past that. He then put 500 miles on it during the 6 months he has owned it, I would not driven it the way it shakes for fear of damaging something else. I did not hammer it, but under load cruising at 50-60 MPH is vibrates BAD. If I let off the gas, is lessens greatly but does not dissappear by any means (lessens greatly is relative!). If I shift into neutral and coast, IT DISSAPPEARS. While in neutral coasting, if I rev the engine, some vibration comes back, but I am not sure if it is the same vibration or just normal engine vibe present in this sort of machine when revved up some or if it is related to the issue at hand. It is not nearly the intensity of what happens under load. When shifted back into gear and under cruise load BUZZZZZZZZZZZZZZZZ, the world erupts again. I thought of something like a beat u-joint, but wouldn't this be almost as bad on deceleration? Is there something wrong with the trans? Weights lost on torque converter or something really broken inside? Can mixing 350/400 flexplates & harmonic balancer parts cause this or would I have felt it the same coasting & revving the engine in neutral? What it boils down to is 1)It is HUGE what happens when shifting into neutral when cruising at 50-60 MPH and making the vibration dissappear, and 2)I really need to make some sort of diagnosis on this so that I can figure out what the car is worth (if it needs an engine or trans this is big in selling price). Thank you very much for your help & time.