oil pressure sender

RonS

What is the  inlet oil pressure entering the bypass oil filter on the 308?

Frankvintagefullflowcom

The port leading to the bypass type filter is exposed to system operating pressure. The only exception is at system pressures below about 20 psi where the port is occluded by the regulator plunger. It's designed that way so as to not sacrifice flow at low pressures (such as idle). Flow rate through the bypass type is limited by a 1/16th orifice located on the side of the vertical discharge tube inside the canister so that oil pressure is largely unaffected at higher rpms.
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RonS

Thanks Frank. A friend of mine asked what is the pressure of a bypass filter inlet was, and if a pressure regulator could be installed to shut down the electric fuel pump in the case of a sudden engine shut off. This is for safety in case of ,let's say, an accident and the driver is unable to manually turn off the electric pump Years ago I set up a system for just that, but I couldn't remember what the idle pressure was needed to keep the pump operating... I thought is was above about 5 psi.  I told him that there are 2 prong senders that will accomplish that result. However, A momentary button may be needed to override the sender since there won't be any oil pressure at start up until the engine  is running.

Frankvintagefullflowcom

I'd agree that a normally open switch in the oiling circuit is a good idea to shut the pump down in the event that the engine quits (crash or?), but a shock sensitive/inverted position safety switch like the ones used in EFI systems is preferable. There has been considerable discussion on this and other forums on the subject and opinions are not hard to come by.
Most such pressure switches close at about 5 psi (as you mentioned) but idle pressure should be well above that or you have other issues to address.
If you should use the bypass filter port for the switch location, it might cause you some grief since it isn't pressurized until the system reaches ~20 psi. Hot idle pressure may drop below that threshold depending on bearing and pump condition which would cause the plunger to retract beyond the bypass port, killing the pump. Yes on the override button.
The above is true of Hudson, but not all bypass filter circuits are made the same way. Chrysler Products flathead sixes and eights (possibly others) are plumbed so that the canister is continually under system pressure and the discharge port is opened and closed by the regulator plunger. In that case, a switch on the canister supply port would be viable location.
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