Hello Troy I decided to use the SC 120 ,but since it had sat around for some time I thought maybe I would change the gaskets ,O-rings and rebuild the regulator and adjust the valves ,fairly simple stuff to do. All was going quite well untill I got to the reg ,Since I have a ton of extra new plungers and springs and a diaphrams this should have been a no brainer. After I got it back together I always check to see if theres spring tension and there was none ,so I turned it in a little more and ,then back it off some still nothing .So I took it back apart and set each piece next to each of the old ones ,just by looking they all seemed to be ok. So I put it back together and still nothing. I thought maybe the hole in the stopper might have been drilled to deep,cast however they build them and that wasn't the problem at all. It turned out the plunger itself was shorter by about the thickness of the head and was bottoming out rather than letting it have a spring load .So I just used the old one and things was fine. According to central all the 120's take the same part no. Could I have just got one that was made wrong or is there somthing else going on here I'm not aware of.

Another item ,none of my other 120's have what they call the regulator ballast and the SC is the only one that shows it being in there. Is this to stop some of the pressure because of the higher compression of this particular engine or is there another reason .

OK one last thing and I will leave you alone you made mention of using a smaller prop on the SC when itis capable of putting out the power of a 140, All of my 120's run a 16X8 APC and are happy doing so. Why the smaller prop for the SC ,wouldn't this be taking a chance of over redlining the engine and floating a valve ???
Sorry to bug you but I appreciate your knowledge on these matters.