Pulley Removal
 

So I bought a new distributor for my 83 GSL. I realized that my pulleys were rusted and I couldn't see the timing marks on them. I bought the racing beat double sheave pulleys. I was doing my research on how to install them when someone mentioned that the bearing behind the bolt that holds in the main drive pulley might fall since the engine is still in my car, and if I attempt to retighten it ill break it and then have to rebuild my engine. Is this true? This is the first rotary I've worked on, and I don't have engine rebuild money laying around as of now. If it is true, how do I install this without taking the engine out of the car? (I'm speaking of the larger bolt, 17 or 19mm I believe, that holds the main drive pulley to the "hub" on the engine)