Propane has twice the caloric heat content of natural gas, measured in btu's per hour.
The orifice sizes need to be 1/2 the diameter that they are now. You have two choices for accomplishing the job. You can solder the present orifice cap holes, and drill them, or you can take samples to a local gas appliance service shop to buy new parts drillled to the proper size. For a drill sizing chart, go to www.joppaglass.com/burner/lowp_chrt.html. You'll also need to replace the gas pressure regulator, if you have one, to one rated for propane use. When the parts have been replaced, adjust the burner air shutters for a bright blue flame, with minimum yellow tipping.
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The information you have given me is common knowledge. I was looking for specific orifice sizes for the franklin Chef GR10C-23.