At home? Your brave! Put some automotive epoxy on a 2.5 x .500 steel rod and drive it in. Use a grinder to even everything out if it if it matters to you as its under the valve cover anyway. Get your best 1/2 inch carbide drill and drill the new hole using measurements . Start porting your intake and when you get close to breaking through the original hole, your iron will turn 50 shades of blue. if you keep going you'll just start grinding into the metal rod, no harm as its a permanent part of the head now. Now all of this can be done at a machine shop too. Loco beat me too it.
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