Started my 77 J10 (401 w/less than 5,000 miles on complete rebuild) and had 0 oil pressure. When the engine was rebuilt I bought a complete timingcover,oil pump, midplate and matched can/distributor gears from Matt and as usual, everything worked great. I had excellent oil pressure until this morning. The gauge is good as well.

I shut it off immediately. Any suggestions guys? Could the plunger be stuck?

Thanks for your suggestions.