80lb oil pump with a 50lb gauge ?

[ottoschmidt]

Hello,
is this why my 50 lb oil pressure gauge pegs instantly all the way over off the map to the right and stays there while running ? I had a 1940 239 8cyl flathead motor rebuilt and just realized looking at receipts my machinist put an 80 lb pressure oil pump in it . There is a 50 lb oil sending unit on my truck . Is this the problem ? It is a stock 1940 oil gauge on a 12 volt system with the voltage reducer . Is changing out the oil pump a lot of labor ? Is there an 80 lb pressure gauge to replace my 50 lb that will fit the cluster ? Will an 80 lb sending unit make the 50 lb gauge read normally ? All help is greatly needed .
Best Regards

[cas3]

many folks here smarter than me, but 80 psi oil does more harm than good. thats for high RPM race motors that are set up with slightly looser clearances to need high volume of oil, not high pressure. if its a speedway, or late model melling, there have been many posts here about the problems with those pumps. an old ford pump rebuilt is as good as it gets. high pressure takes horsepower to pump...less power to the road

[ford38v8]

Not to dispute cas3’s advice, but I don’t believe the difference to be important enough to change out the pump. Rather, you can easily change out the sender, that job being merely a one beer task. The even better news is that you can kick back with your beer and watch someone change it for you job complete in exchange for the 50 lb sender. On the other hand, your rebuilder should take responsibility for his not being alert to the non compatibility of pump and sender. I would go the first route however, and have a cold one with a new friend!

[cas3]

Beer? did someone say Beer? Alans advise is correct. however, i spent my life running construction equipment, and you can not imagine the drop in RPM in machinery when you engage a hydraulic attachment. it takes a lot of power to pump oil

[deuce lover]

Your orig gauge is calibrated to your 50 lb sender.In 46 Ford went to the 80 lb.If you can take the guts of a 46-48 gauge grafted to your 40gauge I don't know. To change the pump you need to pull the pan.The wishbone and drag ling will be in the way.


Here is a 51A 80 lb gauge.Looks like you can switch out the face and it could work.You'll need the 80lb sender which there are a lot of.



https://www.ebay.com/itm/NOS-1946-19...MAAOSwxR1dyZte

[jimTN]

Sponsored Links (Register now to hide all advertisements)

May not make a lot of difference because of the relief valve located in under your intake at the front. If there is not a heavier spring or stretched spring in there, excess pressure should just spurt out there to the cam gear area.

[ottoschmidt]

Alan,
So your answer is that i change the sending unit to an 80lb and the 50lb gauge will not peg over off the map ?

[jetmek]

Originally Posted by jimTN

May not make a lot of difference because of the relief valve located in under your intake at the front. If there is not a heavier spring or stretched spring in there, excess pressure should just spurt out there to the cam gear area.

This!

[TJ]

Changing the sender will most likely solve the problem for you. If you are still concerned about accuracy you can remove the '40 gauge, find a '46-'48 gauge and put the '40 gauge face on it and put it in your dash.

[Charlie ny]

Both my trucks use 80 PSI pumps, 50# Ford gauges and 80# senders. !2v w/ reducer

the gauges read low, but they read.
Charlie ny

[ford38v8]

Otto, yes, that should work for you. To confirm which one you have, your original is either stamped “50” or is not stamped at all. The 80 lb senders are all stamped “80”. Replacement of one to the other is not difficult, but will require the use of a special tool: take an ordinary 1/2” open end wrench, heat it cherry red, and bend it into a U shape such that it will engage the flats of the sender while the handle rises up and over the unit, thereby affording the clearance to turn the wrench without interference with the firewall.

[ottoschmidt]

Referring back to Cas 3 reply , i had a conversation with C&G tech man and another machinist who said running an 80lb pump on a stock motor that is suppose have a 50lb pump is not good . It will wear the motor out and could cause damage much quicker down the road . I have only 280 miles on the stock rebuild and i think i am just going to have to put the correct one back on it to save the life of my motor ... thanks for all the input

[flatjack9]

Originally Posted by ottoschmidt

Referring back to Cas 3 reply , i had a conversation with C&G tech man and another machinist who said running an 80lb pump on a stock motor that is suppose have a 50lb pump is not good . It will wear the motor out and could cause damage much quicker down the road . I have only 280 miles on the stock rebuild and i think i am just going to have to put the correct one back on it to save the life of my motor ... thanks for all the input

These guys are idiots. I have that pump in my engine and have over 60,000 miles on it.

[ford38v8]

Originally Posted by flatjack9

These guys are idiots. I have that pump in my engine and have over 60,000 miles on it.

That’s pretty strong language to use on one of our most respected suppliers. I would not be so quick on the draw having only second hand heresay to go by.
I’m confident that C&G would disavow such a conclusion as reported. No disrespect to Otto, but I feel that there must have been a misunderstanding of fact.

[Hal Beatty]

An 80# pump wearing the motor out??? That's a new one...

Have to keep in mind that all any pump produces is flow; and pressure is simply the resistance to flow.

[ottoschmidt]

In reply , those 2 techies are claiming its all about lash and tolerances . In a performance motor for maybe drag racing ??with looser lash and tolerances a high pressure pump is needed to get into the race and bearing spaces quicker .Where as a stock motor with tighter lash needs less pressure so the oil lubricates better and does not blow by where it is needed . Just what they are saying thats all .

[JSeery]

If you don't want to change the pump right away, you can reduce the pressure by reducing the spring pressure at the by-pass in the valve galley.

[tubman]

I gotta agree with Jack on this one.

[big job]

wondering: have you put a mechanical gauge on the sender port? to see what it
pressure is. So they put a later 80# pump in there in which most have the pressure
relief valve on the pump and you have another the front galley. The 80# standard
pump relief should blow off around 60# cold. You say its a 1940 with a 239? You
sure its not 239 59series that does use the 80# pump. Mercury 239? Did they check
relief spring pressures (don't think so) there are charts for that. I can't name how

many engines people put washers stretched the relief springs for more pressure when in fact it needed bearings. I grew up in dads shop and the golden rule he stressed to see was a nice 40# hot idle and 45-50# at speed. My personal car now
has 7,000 miles 40 hot idle and 60# soon as I take off, a 59A. that means all bearings are at specs, I'm not talking about race loose cars as they say about high pressure I see that. Back in the bus co. buses ran Buick fireball 8's. In ink it stated
any oil pressure under 40# should be looked at. When pressure falls down to 25 30#
the oil alarm would sound and that would cut off the coil. Flathead Chrysler prod.
under 40# and still dropping; Its time for a build. The Ford or a Studebaker has the same internals like a human they are all the same. What if you have high or low blood pressure same deal......

[Ziggster]

Don’t pumps just produce flow? I thought the oil restrictor and resulting passages produce the resistance to flow = pressure.