Started a 671 in champion grader that hadn't run in 10 yrs, started stupid easy but ran up to gov possibly more, cut fuel and got it shut down, looked things over and tried starting, fired up again and did the same thing again. So is the rack stuck? What else should I look at?
Depending on what type of rack it is one injector can stick the whole rack and frequently does when it has sat so long. There is another type of rack that only that one injector will stick. The governor is not in play when this occurs, it is full fuel to the moon. Pulling the rocker cover is easy and might give you some idea if you know what you are looking for. You are supposed to replace any stuck injectors but I have had good luck with chucking them in a lathe then running the tailstock down onto the plunger while pulling the fuel rack in and out with a stream of WD-40 going through the ports. It seems to wash the gunk out and then they work OK. Consider the consequence of any action and make sure the rack is free before you try to start again. The instructions must be out there somewhere and they aren't hard but there are some critical steps.
When you start it again it is advisable to have a board or some other "plug" to slap over the intake if it runs wild.
The 6-71's I worked on, and for that matter all the Detroits I worked on had the system where one stuck injector locked the whole rack up. It's pretty easy to identify as there is always some wiggle in the fuel rack and once you have the valve cover off when you wiggle the control tube you will see which injectors are moving and which one(s) are locked up. Just to get it running you don't need to run the whole adjustment, repair/replace the offending injectors and adjust the lever for just the ones you've replaced to match the rest as closely as possible at dead rack. If everything checks out, runs good, good oil pressure then get the proper GM timing tool and run the valves and the rack completely for best performance. Good oil pressure on these old dogs if they have the long horizontal bypass filter is anything at all with oil hot at idle. 15 psi hot at idle is fantastic. I agree with the others of course, make sure the air emergency shutoff works if this engine has it (most did) and it's best to open the intake up at some point where you have a flat surface to slap a metal clipboard or piece of 1/2" plywood over to choke it off as a last option before the revs get so high you're afraid to get near it.