Those work ok for stock springs, and flat-tappet springs, but not anything more. I have the same thing but you can drive it with a 3/8" ratchet and it still sucks for 300+lb springs

 

If you have a high spring height that tool will not work at all. Already bought it and now I have no use for it.

Here is a link about the tool that I tried to use.

http://www.teamandersonracing.com/ToolPic.htm

For stock replacement springs maybe up to a LT4 type spring will work ok, but be careful when using any aftermarket, high seat pressure springs.

 

I just changed all my springs with it.

The only tricky part is getting the spring line up so that when you're compressing it, it is straight and not pushing the valve down. Also, instead of trying to put the locks in their individual side, stick it in the part of the tool that has been "opened up" a little, on the side closer to the stud, then slide it around to the other side and then put your other lock in. Makes sense when you start doing it.

Ken, I had the same problem as you. I had to physically push down on the spring to get it to barely compress, while leaving the tool and 1 washer on the rocker stud, the washer will catch on the threads and hold the tool. Eventually you can get enough studs poking through to stick the nut on. After you get a few threads of engagement you need to situation the spring so that it will compress correctly.

If nothing else, use this tool to take them off, and a screw type to put them back on. I took off 987s and put on 918s with this tool last week.