please help

Is this with the car just in the driveway and idling? Assuming all the accessory items on the front of the motor look good when running i.e. in good alignment and not wobbling? What transmission is in the car?

You have to understand that we need details as to the build, Have you done anything except fire it up and :poo: your pants? What imbalance is the motor? Is it an old school 302 or newer roller motor with a 351W firing order?

I can literally say the less you tell us the less we are or anyone for that matter can be any kind of help. So summing it up the more details on the car and the build and what you have done to date as far as solving the problem are all super helpful.
 
I have a 65 mustang and put a crate motor 302 in it. Today I fired it up, started fine but I get a vibrating rub sound and can feel the vibration. Any ideas what it may be?? I am thinking possible misaligned starter? thank you

I will say that with this level of description and troubleshooting that you need to take the car to a mechanic.

It is very possible to cause more harm than good otherwise.