Now for the question(s) Pump timing on the 24 HP engine is advanced due to higher engine speeds and as youall know that is done by running the bolt up on the cam follower. Has to be hard on the pump and cam and drive to be jamming the pumps against the internal stops right?? Timing is set correctly now so what do I do? back the timing off so the plunger isn't being pushed tight? What will retarding the timing do to performance at rated RPM. I think it is 1000 RPM for the 24/2.
Thanks
As you have correctly identified, if you continue to advance the pump. You will eventually get a situation arise where the the pump plunger element inside the fuel pump is making contact with the underside of the delivery valve holder. This is not a good situation to have as you will quickly damage the element and delivery valve (d/valve) as these items are most delicate, when compared to the cam follower and lobe.
I cant comment on Listeriod engines (because I don't have any, so don't have to endure these type of problems
), but on a genuine Lister engine, you should never need to run with an amount of advance sufficient for the the above situation to occur. However if as you say the spill timing is now correctly set, you may be suffering from a manufacturing defect within the pump itself, which is preventing you from obtaining the correct spill cut off point before you run out of adjustment and the plunger makes contact with the underside of the d/valve.
Firstly I would try another element in the pump, as the helix position on the plunger may be where the manufacturing error lays, if it still persists then try another pump. Finally if the problem still persists put a spacer between the top of the element and the delivery valve (I know this is a bodge up solution, but it would save further damaging your pump internals and could cure the problem).
Unless you drastically retard off the the timing your not going to notice a significant drop off in power, what you will notice is starting will become harder, and exhaust smoke visibility will increase.