| jec13 | -- 04-27-2023 @ 11:41 PM |
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I have a 1935 Ford Model 48 5-window coupe. Engine is the factory 221 cu in 85 hp V8 as original. Starts, runs and drives as it should, smooth, good compressions, full power, clean, no sludge, no noise, no smoke. The engine was rebuilt 1,500 miles ago by the previous owner. Problem is oil pressure, too high at driving speeds. Cold start oil pressure is 30, then as the engine warms and RPMs increase with driving speeds, oil pressure creeps up to 55 lbs. This pegs the car’s electric 50 lb oil pressure gauge. Slowing to idle, pressure returns to 30-35 lbs, but then at driving speed, it is always up to 55 lbs. I have twice verified pressure readings with separate mechanical gauges. Pressures behave essentially the same with both 10w30 and 20w50 oils. I pulled the intake manifold and replaced the oil pressure relief valve and spring with correct new parts; the result of that was no change in oil pressure behavior, still 55 lbs at driving speeds. Now I am stumped. A properly operating relief valve should balance the system to normal pressure range. What else could be causing the high oil pressure? Perhaps a blocked oil passage? What should be my next steps? Thank you for your help.
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| pauls39coupe | -- 04-29-2023 @ 7:09 PM |
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WAG the bearing may be tighter than the average engine, but with 1500 miles on it no noise or leakage you probably don't have a problem. Anyone else have a guess??
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| Grant | -- 04-30-2023 @ 6:11 AM |
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I agree with Paul. Your coupe's engine may be fine. We have a '52 engine that idles at 35 psi, and that's on a Stewart Warner gauge which should be pretty accurate (live copper tube pressure line, not electric with a sending unit). What is your heat gauge telling you?
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| carcrazy | -- 04-30-2023 @ 8:32 AM |
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If when the engine was rebuilt, a later flathead (80#) oil pump was installed, the 50# gauge will be pegged while the engine is running at road speeds. If the rear main seal was not upgraded to handle the increased oil flow and pressure, you will have a massive oil leak at the rear of the crankshaft anytime the engine is running.
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| jec13 | -- 05-02-2023 @ 5:05 PM |
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Thanks everyone, for your responses. The seals are fine, no leaks, and engine temperature is normal. Just wanting to get ahead of a possible problem due to the higher oil pressure. I think I will pull the intake manifold again and try a lighter spring on the oil pressure relief valve. And, check for blocked passages.
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| TomO | -- 05-04-2023 @ 2:31 PM |
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It sounds like you have the later 80# pump installed and you should use the 80# oil pressure sending unit. This will give you a reading that will be in the range of the gauge. Full scale will be 80#, half scale will be about 40#. I would leave the oil pressure relief valve alone and change the sending unit. Try to find a good used one as the reproduction units are not very good. Changing the pressure relief valve will not correct that sending unit / oil pump / gauge mismatch. The 80#pump pressure will not hurt the engine and if the valves were changed to the 8BA style they will need the extra pressure. Save the 50# sending unit as they are getting harder to find and someone can use it. Tom
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