Ok, have a think about this.
Engine - SRM build with SRM oil pump, Wiseco pistons, 3000miles, oil pressure gauge, return oil filter, oil cooler, 20W50 Silkolene Comp 4 oil, runs well.
Problem - A week or so back I had just got about a 1/4 mile from home when I noticed that the oil pressure, which is normally about 65/70psi cold, was falling rapidly to the 'oh my god' level, i.e. maybe 5/10psi. If I let it tick over it comes back up again which led me to think that the pump was being starved of oil at its inlet. Normally, when fully hot during a high speed run , it would run at 25/30psi and hold 65/70psi for maybe 10 miles or so depending on how fast I was going and ambient temp.
Action so far -
Oil level in tank - ok
There is no valve in the oil line to have left closed (before someone suggests I open the valve)
Drained oil from tank
Checked the gauze filter in the tank - ok
Removed the oil line to the engine and confirmed it is clear and not blocked.
Blew through the fixed oil line inside the tank - ok
Removed the timing side cover
Removed the SRM pump
Dismantled the SRM pump and all inside is in mint condition.
Checked oil pump drive - ok
Blew through the oilway from the outside of the engine casing to the pump inlet port - ok
Passed a wire into the inlet oil way until I could see its end at the oil pump inlet port - ok
Removed and dismantled the SRM PRV - ok
Reassembled it all and test rode it again - same result !!!!
Fitted a standard PRV in place of the SRM PRV and same result only 50psi with this PRV.
Refitted the SRM PRV.
Any suggestions gentlemen?