Young grasshopper, you can use the Berk Impeller Charts and cross reference your impeller cut and RPM. If your impeller has been reworked by Jack or one of the other pump guys, the Berk Chart becomes more inacurate.
You can also use the Jet Performance Calculator which can be downloaded here by clicking on the "standalone JPC" graphic.
Both this tool and the Berk charts are ballpark figures, your results will vary somewhat. If you want, I can run a desktop dyno on your engine, plot that curve against the corresponding impeller curve from the Berk charts and email you that in an excell file. Just email me the particulars on your motor and I can get you the rest.
Chris
[ September 19, 2002, 10:00 AM: Message edited by: flat broke ]