I glanced over all of the other comments, and here's my advice. Get all the split shot off the line, and cast with a short leader and tuft of yarn. Start at shorter ranges, and work your way out after you get a feel for the rod's tempo. You didn't say you were trying to blast out a 70' cast, but it's not too hard to imagine someone trying to do that with a rod like this.
One of the things I learned a long time ago, is that it's nearly impossible to cast your way out of a bad situation. Watching my wife over the past 7-8 years has allowed me to see what someone might be inclined to do without a coach of some sort. I tell her to just let the line fall, and start over. Double hauling requires really good timing with a rod like this, and what you were able to get away with on a 4wt won't work as well with the 8wt. I taught myself how to double haul, but had to watch videos for about a year before it sank in. Smooooth
hauls work better than sharp jerks.
8 weights are a different game, but you should be able to get it done.