A year ago I swapped the polyurethane motor mounts out of The Crusty Chevy for rubber, in an effort to chase down a vibration. The poly was not the culprit, but the replacement mounts had their own issue.
Today I swapped them back.
Left to right, you see “Anchor” made in China, “Anchor” made in USA, and the original clamshell with the poly mount installed.
Looking at the ends, you can see the USA mount had completely collapsed and had deteriorated. This mount was actually faulty from day one – the metal supports for the motor were actually touching the clamshell on the inside, producing a horrifying (and slowly increasing) metal-on-metal vibration exactly at cruise RPM under light (cruise) throttle. I finally had enough, and pulled them out and went back to poly.