flathead oil pressure senders

[f1builder]

can anyone explain why an 80# oil sender would not work in all flatheads and what the diff is between the 80 and 50 in practical terms? i have interchanged these over the years with no issues and haven't spent much time thinking about it.

[Henry/Kokomo]

I strongly suspect the different "senders" have different electrical resistance. The sender regulates the current seen by the oil pressure guage. The resistance of the sender would have to be matched to the gauge to get an accurate reading. If I'm wrong, hopefully someone will correct this post - and earn my thanks at the same time.

[f1builder]

i contacted a supplier that said they sell 80# senders for all 35-53 flatheads but i am still unsure.

[deuce lover]

35-41 use a 50# sender which is difficult to find.I had an 80# sender in my 35 and it did not read correctly.When I found the 50# and changed it ,all was good.I suppose the guage and sender should be compatible.

[ford38v8]

The 80# will work, but calibration will be wrong. I'm not sure which, but you'll get either .625 x or 1.6 x the correct reading.

There were two identifying features for a 50# sender, either it was marked 50, or had no mark at all. All 80# senders are so marked.

[ken ct]

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Originally Posted by ford38v8

The 80# will work, but calibration will be wrong. I'm not sure which, but you'll get either .625 x or 1.6 x the correct reading.

There were two identifying features for a 50# sender, either it was marked 50, or had no mark at all. All 80# senders are so marked.

Does anyone know this second statement by 38 is definately correct were some 50's NOT marked?? ken ct.

[f1builder]

i have 2 of these senders left and neither are marked. one came out of my 53 merc motor and one was on my 40 ford motor and they look identical and neither have any marking except for a very small circled number or symbol that looks like a 2.

[ford38v8]

Original '35 - '41 senders were not marked. When the 80# senders came in, there was the need to identify the difference, so from that point forward, all senders were marked, at least while the 50's were still being supplied.

F1builder has now thrown a monkey wrench into the discussion, so maybe someone can pick it up from here?

[Terry,OH]

I agree with ford38v8 that from my experance the early 50# was not marked. I have not seen a 80# unmarked. I also believe the 50# sender was marked upon the introduction of the 80#. It is possible the unmarked sender out of a 53 Merc is a 50# and installed inproperly to give a higher oil pressure reading on the gauge.

[41ford1]

I agree you need to match the sender scale with the gauge scale. A 50# sender must be used with a 50# gauge and the same with the 80#s. However, I did find that a sender for a 302 in a 1980 F100 does work accurately with the stock 50# guage in my pickup. The sender I was sold for the application is a Standard Motor Products partno PS-60. 3 years ago it cost $25.00, available locally and was made in the USA.

[John Kennedy]

Different senders have different ohms ranges, that is true. Senders must match the gauge. Henry / Kokomo is right on this.

[4dFord/SC]

Originally Posted by f1builder

i have 2 of these senders left and neither are marked. one came out of my 53 merc motor and one was on my 40 ford motor and they look identical and neither have any marking except for a very small circled number or symbol that looks like a 2.

Possibly "KS," the trademark of King-Seeley who made these units?

[rotorwrench]

No telling how many "aftermarket" senders were made or whether they were all marked with the psi rating. If they were made by King Seeley they generally always have the trade mark KS in a circle stamped on there.

Kerby

[BrianCT]

Originally Posted by 41ford1

I agree you need to match the sender scale with the gauge scale. A 50# sender must be used with a 50# gauge and the same with the 80#s. However, I did find that a sender for a 302 in a 1980 F100 does work accurately with the stock 50# guage in my pickup. The sender I was sold for the application is a Standard Motor Products partno PS-60. 3 years ago it cost $25.00, available locally and was made in the USA.

Are you running 12 volts neg ground?

[JM 35 Sedan]

There is a commercially available sending unit that can replace the original 50# sender and works correctly with a 50# gauge. I believe it is/was used on a Jeep/AMC product. I have this info saved in my computer files which I do not have access to at the moment but could post later if anyone is interested.

[Steve/IL]

John,
Please post the Jeep/AMC part number for the oil pressure sending unit. Thanks!

[Cecil/WV]

I got one from Kaiser Willys Auto Supply for my '40 pickup, but I have no part #. $36.74

[41ford1]

BrianCT,

Yes the system was converted to 12v neg ground, I am running the stock gauges using a 6v Runtz reducer on each. The gauge and sender will operate the same way on either polarity as long as only 6v is applied.

[ken ct]

Ive looked up the jeep unit in the past,it obviously works but not quite a duplicate of the original. Its taller i remember so would not look right if going for points for those of you who care about that stuff.Probebly a point deduction on it. For me i wouldn't care a hoot. ken ct. This was a good thread,maybe we all learned something.

[41ford1]

F1builder,
Here is an attempt to answer your original question. From what I've observed by exploring a number of the Ford indicator systems is the gauge units are basically the same. Meaning it takes the same electrical energy to move the pointer from 0 to full scale. The pointer is moved by putting current through a heater wire wrapped around a bi-mettalic arm. More current equals more pointer deflection. The original senders use a similar heater wire bi-metallic strip. The strip is attached to a set of points. One side of these points is tied to the sensor element. In the case of the OP it is a diaphram. The diaphram actually establishes the range for the sensor. So if a 80# sensor is used with the 50# gauge when the sensor sees 50# the guage will show about 30#. Inversely a 50# sensor seeing 50# will show 80# on an 80# gauge.

Sorry this got a little long.

[JM 35 Sedan]

OK Barners, here's what I have in my files. This was info I copied on Shelly's old Fordbarn. I assume it's correct but have not tried to purchase one. As ken Ct said, they may look a little different than an original Ford sender so they would not be show correct for EFV-8C/A judging on the show field.

Oil Pressure Sending Units:
The sending units were manufactured by King Sealy and have a KS logo stamped on the top. They made 50# units for Willy's, Kaiser, Packard, and others. Let you in on a secret, essentially the unit was the same 50# pressure unit. The difference from Ford was the thread that fits into the block. Ford used a larger thread. I have found the Willy's (PN 647571) and using an off the shelf adapter have been able to fit the sender into the Ford V-8 without affecting performance. Look for these on ebay or at a Jeep parts house or auto parts store.
FordBarn Post by Bill Worzek:
Kaiser Willy's Has the 50# senders...They have the 50# sending units, But like mentioned below smaller thread so a adapter is needed for Ford application. The Part is made in the U.S.A. by Crown the part # is 3212004 You can contact them At: [email protected] Another good supplier JMO

[f1builder]

thanks to all who responded, it has been very interesting and informative.

[Kube]

Originally Posted by ken ct

Does anyone know this second statement by 38 is definately correct were some 50's NOT marked?? ken ct.

Ken,
Ford started marking '50' on units nearing the war years to differentiate the "new" 80# units from the earlier 50# units. Before that only 50# units were utilized and manufactured so there was simply no need to differentiate them.

The sending unit must be matched with the dash gauge in order to read accurately.

KS is in fact King-Seeley, the manufacturer's trademark.

[Ray With]

Well from reading all the post the correct units are available and I would think with using a radio shack resistor you could make the 80# work with a correct gauge reading. Just my thoughts.

[34flathead]

here is on on ebay today and it has the part # referencing the old # 3212004, ebay item 160554846227
rich

[34flathead]

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another one NOS ebay item 270133513322
rich
Please wait
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[ford38v8]

Hey now! Renault, you say? Not helpful at all. :/

[DD931]

OK, you got me interested. I checked the barn and found two sensors. One is marked with a "Script" F followed by -80. It also has a "Script" F followed by 1-8. The 80 I can understand. But the 1-8? It also has an arrow marking "UP". First time I ever noticed that there was an "UP"!!

I also have one marked KS in a circle which I assume is King Seeley. Does anyone know what the "9" under the KS indicates? Those are the only markings except the "UP" arrow.

I'm sure I have a 50# unit on my 48 F-1 because I get a full scale reading (no numbers) most of the time, rather that just above half which would be expected. Time for a change with the one just described!

Norm

[Bruce in southern OH]

I want to Thank JON ANDERSON for his help with the 1935 oil pressure gauge and his time and effort. Today I removed the rubber floor mat, gas pedal linkage, clutch pedal foot pad, brake pedal foot pad, screws the hold floor board down, and then I could reach the oil pressure sending unit, tried a NOS sending unit that again would not make sending unit work. Looked up the search on Fordbarn and found this old thread, exactly what I was looking for, traveled to NAPA and they crossed over the Crown # and I got a ECH Oil Pressure gauge switch # OP6603 and one 1/4 to 3/8 inch brass fitting, drove home and installed, works like new, 30 PSI at an idle, ( checked with my Air Compressor gauge installed in flathead block ) Again the fordbarn came to the rescue, thanks for all the information, Thanks JON
( will start the re-installation of floor mat, etc this evening )

[oldford2]

Since the sender is a bugger to get in and out, I put a 5" long 3/8 pipe nipple in the block where the sender is located and then with a 3/8 pipe coupler mounted my sender. Now it is up where it can be taken off easily. Now, attach a mechanical pressure gauge on the nipple and read what the actual pressure is at idle (maybe very low) and then at say 1500 rpm. Now put whatever sender you have and read what the dash gauge says at those rpm's. So now you will know how to interpret the dash reading vs the actual pressure. Clear as mud??
John

[34flathead]

Bruce, glad it worked out for you, but i searched napa and the part # ECH OP6603 discription is for a 100 psi oil sender.
rich

[Bruce in southern OH]

I know, but that is the cross over for the Crown # that is listed above, now either I have very good oil pressure or whom ever listed the Crown # knows something I do not, it reads on the stock gauge the same as what the Mechanical gauge did with in a couple of pounds, go figure???? I know that now when I start the motor, the little oil pressure needle slowly makes it way up the gauge, THAT'S GREAT! as Tony the Tiger says. Tell me more if you can explain, just glad to have a working gauge. NOW, I need to get a working 36 gauge that I installed in the same dual gauge, ( oil pressure and fuel share gauge ) I installed a 36 fuel gauge which is electric, I need to look up how to install a 36 sending unit in a 35 tank, told I need to change tanks, thanks again Bruce