Flathead oil pressure problem

Hello, I have a newly rebuild 1942 motor with full floating bearings, it has the long body pump, it has 30 psi wile driving and 25 at idol, but sometimes the gauge will drop to almost zero and then slowly come back up, I took off the line and oil was shooting out. The pump has a new kit in it, the gear on the back of the cam is not loose.

Is it possible the pump has too much clearance or something?

 

Verify with another known good oil pressure gauge.

 

That was the 1st thing I did, I have tried 3

 

Know nothing about flat head oiling. That said, is it possible that it is pumping to much oil that it’s all up top (figuratively speaking) then when enough oil finally settles back down things are good again?

 

Did you check the pumps clearances?
Maybe the pressure relief spring is weak(?).
Any oil gallery plugs that could have potentially not been reinstalled?

 

New pressure relief valve spring and plunger, it dosnt donit all the time only occasionally so cant be a plug.

I have sent some more pump bodys off to get hot tanked and I will put another NOS kit in one, its the only way to rule out the pump.