Bad motor mount?

[EP429]

Just need a little input since I rarely get time to crawl under my hood anymore. If when I step on the throttle and I can feel the clutch pedal lift a bit, is this evidence of a bad motor mount?
I've been fighting with a vibration forever that I can never seem to chase down, entire ignition system is fine, balancer etc is good, only vibrates when engine is on (I have done a rolling test) think this is my culprit?
Short of a mis-balanced clutch assembly I'm out of ideas

 

[2+2GT]

A bad motor mount won't make it vibrate, but it could make a vibration more obvious. Check the mounts. The left one usually fails first.

 

[HookandLadder]

With the hood open. Put some torque on the motor. You will probably see it visibly rise up..........left side usually.

 

[robbz28]

I have a similar issue with my 67, mines auto, but whenever i romp on it the engine torques about 20 degrees or so, the drivers side rises and kind of scares me, but all the bolts are in and it seemed fine when i put the mount in there (factory rubber/steel mounts) is this amount of twist normal?

 

[2+2GT]

I have a similar issue with my 67, mines auto, but whenever i romp on it the engine torques about 20 degrees or so, the drivers side rises and kind of scares me, but all the bolts are in and it seemed fine when i put the mount in there (factory rubber/steel mounts) is this amount of twist normal?

No. A 2° shift would be OK. 20° tells me the rubber center of the mount is sheared, and your mount is now two pieces.

 

[robbz28]

Yeah, it really twists, im going to go ahead and buy a replacement. All that horsepower, just ripped it in half =D , lol.

 

[HookandLadder]

More than likely the heat shield was not put on with a new mount and the rubber prematurely dried out and failed.