Originally Posted by xsperf
you probably have something else wrong, something else that is making your engine vibrate or move around which puts a ton of stress and wear and tear on your engine mounts, it could even be rough idle, and a misfire, because w/out all 8 cylinders firing correctly it throws the engine's balance off(not as noticeable in a v8, but in an I4 definitely noticeable)
no, its not missfiring. it was a little when i first bought it, but i replaced the plugs and wires and it stopped. and at idle, it runs very smooth for an old V8. cant feel it in the cab or anything like that. the only other thing i can think if is, when its first warming up when i start it, it idles at 300-400 RPM and vibrates quite a bit. but after about two or three minutes its fine and goes back up to its usual 550RPM idle. i wouldnt think thats enough to kill the motor mounts so soon, but i guess it could.