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38 coupe · 04-19-2012, 07:08 PM

With all due respect to other people's opinions here, flow is not all you need in plain bearings. The oil does more than just lubricate, it prevents metal to metal contact. The pressure of the oil in the main and rod bearings has to be greater than the pressure downward on the applicable bearing. Radial force goes up with the square of the velocity so you need much more pressure at higher r.p.m. than you do at idle. Ford calculated the average pressure on the bearings at the highest expected r.p.m. and set the bypass valve to just above that pressure. As the power went up in the flatheads, so did the bypass valve pressure.

That said, I do not worry when my 37 has 10 lbs or less at idle.

04-19-2012, 07:08 PM	#21
38 coupe Senior Member Join Date: May 2010 Location: South Texas Posts: 1,680	Re: Flathead Engine Oil Pressure ? With all due respect to other people's opinions here, flow is not all you need in plain bearings. The oil does more than just lubricate, it prevents metal to metal contact. The pressure of the oil in the main and rod bearings has to be greater than the pressure downward on the applicable bearing. Radial force goes up with the square of the velocity so you need much more pressure at higher r.p.m. than you do at idle. Ford calculated the average pressure on the bearings at the highest expected r.p.m. and set the bypass valve to just above that pressure. As the power went up in the flatheads, so did the bypass valve pressure. That said, I do not worry when my 37 has 10 lbs or less at idle.