Technical Help Me Understand Ford Flathead Oil Pressure

OK, I know the prevailing theory is don't even worry about it, however the spec for my v8-60 calls for 30psi at 2,000 rpm. I started with about 20 psi cold and nothing warm so I shimmed (over shimmed, hoping to work back) the relief spring.

Here it is on cold start, high idle on choke. Temp gauge hasn't budged. Pressure 80 dropping to 65 after maybe 15 seconds.


https://www.youtube.com/watch?v=1MPikwV_DJY


And here it is 2 miles and maybe 5 minutes later. Temp gauge about 150. Pressure 0 at idle, 15 at best at 2,000. The pressure actually started dropping sooner but I couldn't pull off the road to video.

https://www.youtube.com/watch?v=PJCdtO9S0VA


Straight 40w oil. Engine has no hint of a knock. Full floating rod bearing. I just can't understand how pressure could drop so drastically so quickly, oil barely even warm. A v8-60 differs from the larger flatheads in that the oil pump is bolted to the front main cap. The oil pressure gauge take off is at the back of the intake manifold, so (I'm guessing) the crank and cam bearings have been fed prior to oil reaching the gauge. So perhaps the bearings themselves are seeing more pressure than the gauge, but it still does not explain how it can read so high at first.

Any explanations, crazy or otherwise?

 

The oil pressure relief valve is located under the intake manifold at the front of the block. The spring could be weak or sticking until the motor warms up. Was the motor re-built or used? Try another oil pressure gauge, yours could be bad.

 

how are the main bearings????? one of the symptoms of oil pressure drop
after running a while.

 

I certainly suggest putting another gauge on before doing anything major. I once shotgunned an oil pressure issue on a quiet running 240,000 mile engine. Made the ***umption it was time for a rebuild, nothing looked too bad and the crank did not need turned, still had very low pressure after build until I replaced the gauge. Never made that mistake again.

 

Are you using an oil pressure gauge with a sending unit? Or a mechanical pressure gauge? I had one with a stock pressure gauge that was reading poorly. I installed a mechanical gauge and it read correctly.

 

X2. AND, the electrical gauge was a NEW Stewart Warner! (happened many moons ago...)

I have a mechanical oil pressure gauge hooked to a high pressure flexible line 18" long.
ANY suspect of low oil pressure is checked with this test gauge.

Universal fit: "Everything goes to 1/8" pipe."

 

Thanks guys. It's a mechanical gauge but I'll try another one tomorrow.