I have a BMW 1996 323i and replaced the engine with a 1994 320i engine, not the car shakes when i start it, and while pressing the brakes to shift the car the hshaking gets worse, but once the car get going it runs, the other day when I cut the car off it took a while to start, and then I smelled gas fumes. the mechanic said he could not find the head gasket so he patched it up with cilicone, is this safe? Also the button on the shift to put the car in reverse and drive, it is push all the way in and it feel kinda tight, and not a lose as it used to be before I took it to the mechanic. What could be wrong with the shift handle.
Thanks for your imput to these my concerns.
Stephanie Collie