Re: M103 Oil Filter Check Valve
The OEM filters have two valves. One is the rubber diaphram type anti-drainback valve, and the other is the filter relief valve in the center of the filter. The later opens in the event that the filter becomes clogged. Don't know the spec, but on most engines it's about 10 psi, and on most engines the valve is in the filter pad, not the filter itself.
I have an inventory of Bosch 72165 filters which have both valves. A few weeks ago when I was at Autozone I noticed they had a Bosch filter for the M103 engines, but it was a different number and didn't have the bypass valve !!!???