I bought 2 sets of replacement blocks last year. They felt gooey sticky and soft. As if I could easily rip them apart. I installed them with a new engine in a used Viper 120 and the plane sat all winter. Never run.
This weekend I took the plane out to break in the engine and noticed the rubber was cracked? I started the plane and the engine nearly fell out. All four blocks had failed. The only thing holding the engine was the nose ring.
I took the rubber out in pieces and installed the second gooey set. Try it again next week.