| scooterb84 | -- 01-23-2025 @ 11:21 AM |
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Hello. Wanted to get a recommendation on which lb. oil pressure sending unit to get. I have a 46 Ford with a 51 8BA flatheaed and the oil pressure gauge in the car reads up to 50 lbs pressure but I hear a lot of people say get the 80lb sending unit on many forum posts fore my engine. If my gauge only goes to 50lb shouldnt I get the 50lb sending unit? Reason for this is my gauge as of lately has been reading somewhat normal at startup but then once it warms up falls to 0 and doesnt move much even while driving which is not normal behavior compared to months ago. I feel my sending unit may be bad and want to try and repalce to see if that rememedies the problem. Oil and filter changed recently using 30w and is at good safe level on dip stick. Ive always used 30w and never had this problem until recently. Car is running strong and no indication of any issues other than the low pressure reading. Thanks for any advice! This message was edited by scooterb84 on 1-23-25 @ 11:33 AM
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| ford38v8 | -- 01-23-2025 @ 2:25 PM |
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Scooter, your sender should match your gauge as you know, and has nothing to do with which engine you have. The fact that your gauge registers at startup and drops to zero at operating temp indicates that the sender and gauge is functioning properly, and is telling you that your choice of oil may be upgraded to help your engine and your peace of mind. A straight 30 weight oil is no longer recommended for internal combustion engines for several reasons. A good multi grade detergent oil changed regularly along with the filter should make a slight difference in your pressure, depending on that choice. You may experiment with different grades, but with the knowledge that all you need at operating temp is a slight movement off the zero mark. Alan
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| scooterb84 | -- 01-23-2025 @ 3:01 PM |
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Thanks Alan! Appreciate the reply! Flathead oil research online is literally all over the board. Years ago when I researched this 30W seemed to be the clear winner but that seems to have changed. Ive never had issue running this but if there is a better oil I am all ears. I was looking at the Lucas Oil 10w 40 which is made for older flathead engines and has high zinc. Any recommendations there? Again, thanks for the reply and your time!
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| ford38v8 | -- 01-23-2025 @ 3:46 PM |
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Scooter, Lucas 10 40 is a good choice, as are most other modern multi weights, as your question will undoubtably bring some of those recommendations. The issues to consider are: detergent VS non-detergent, viscosity, and zinc content. The use of detergent will simply require your closer monitoring of how often you change oil & filter, and will slowly improve sludge conditions in your engine. Viscosity being your initial concern, wil depend on your findings. More or less zinc will have negligible effect on a basically stock flathead engine. Edit: I meant to say the use of Detergent oil, not non- detergent oil. I made the correction above. Alan This message was edited by ford38v8 on 1-23-25 @ 9:58 PM
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| carcrazy | -- 01-23-2025 @ 5:10 PM |
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Here are my suggestions to answer your questions about what oil pressure sending unit and what oil to use in your third generation Ford Flathead V-8 engine. For maximum peace of mind use a mechanical oil pressure gauge to monitor your oil pressure under all operating conditions. Stewart Warner makes a good gauge which is available with a lighting kit and a mounting panel that you can attach to the bottom of your instrument panel. The correct Oil Pressure Sending Unit for your late Flathead V-8 which uses an 80 lb. oiling system with the higher output (80 psi) oil pump is Part Number 41A-9278 which is available from several of the vendors. You would want to also obtain an electrical 80 lb. gauge that is compatible with your sender. If you ask 100 people what oil to use, you will get 100 different answers. Here is my recommendation, use a straight SAE 30 Detergent conventional Motor Oil plus an additive which contains the proper amount of ZDDP (zinc and phosphorus). One of the oils which is suitable is Pennzoil SAE 30 API Service Rating SN or later. A suitable additive to use in conjunction with this oil is Red Line Engine Oil Break-In Additive, just follow the instruction on the label for how much to use. Hope you are able to put your oil pressure anxiety to rest. In the past I had similar concerns until I used mechanical oil pressure gauges. This message was edited by carcrazy on 1-23-25 @ 8:54 PM
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| JayChicago | -- 01-23-2025 @ 8:01 PM |
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Have to respectfully disagree with Carcrazy on which sender to use. The sender has to be matched to the GAUGE. The sender is part of the gauge. It is the control circuit for the gauge. Doesn't matter what oil pump is in the engine. For a gauge to read correctly, it has to have the sender calibrated to work with that gauge. A 50 lb gauge needs a sender calibrated to move the needle full scale at 50 psi. An 80 lb sender will give inaccurate readings on a 50 lb gauge. Thanks to professor TomO for teaching us this, on this forum, several years ago.
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| ford38v8 | -- 01-23-2025 @ 10:05 PM |
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Jay, in carcrazy’s defense, he did say to get an 80 lb gauge to match the sender. I do, however, disagree with his choice of oil and additives, but only in that it’s a waste of money. Alan
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