340/420 90psi Oil Pressure During Prime

If, when you fire the motor, oil pressure is still in that range, I would keep a close eye on it.

I had a newly built 340 with a high pressure? or volume? pump (I don't remember). The oil pressure was on the high side and it buckled the oil filter outward away from mounting surface and blew oil all over my engine compartment and the street. All this 18 miles from home.

In another instance, I lost oil pressure as the pressure was high enough to shear the cotter pin in the oil pressure relief valve (in the pump), leaving the valve constantly open. I had to put a thicker cotter pin in the pump to fix. Stuff happens.