80 lb oil pump in 1935 flathead - is this okay?

[Model51]

The engine rebuilder installed an 80 psi oil pump in my 1935 flathead block. The rest of the engine is stock. Since the original pump has a 50 psi limit, will the extra 30 psi cause any issues? I assume (a bad thing to do) that there is a oil overpressure limit function like a spring relief valve so the system pressure won't exceed 50 psi at some point in the system. Can I check this somehow?

The engine rebuilder ran the engine for a short time and according to him it functions okay, but I have not run the engine. I'll be installing the engine and testing it this winter and have a chance to make any changes if needed. I figured the guy knows what he's doing (maybe another bad assumption?).

What do you guys think? Am I good to go or should I replace the 80 psi pump for a 50 psi unit?

[glennpm]

I would change the pump. The Flathead and it's low maximum RPM, does not need this much pressure. The excess pressure will probably give you oil leaks though such as at the rear main seal.

BTW, I just did this change on a SBC I have. The replaced pump operated at around 75psi. The new Melling standard pump operates right around 50psi and leakage issue has been resolved.

Glenn

[Ron_r1959]

If its a 1935 21 stud block, it will have a pressure relief in the intake valley near the front that will relieve it at probably something near 50 psi anyway. Assuming that hasn't been shimmed, you should be ok. To my understanding, the early pumps did not have a pressure relief on them so they installed a relief in the top side which to my way of thinking was not a bad thing. later when the 8Ba blocks came out, they removed the top relief system and put it on the pump itself like all the modern pumps currently do. At some point since the pumps are interchangeable anyway, they quit making the early style pump and since then everyone uses the later style pump. The flathead oiling system was pretty good and unless you are racing it with extra clearance, there is no need to install a high volume pump or run high pressure either, that being said, The reality is, that whichever relief is the weaker, will control the pressure so if you don't like it, you can change it in the valley pan anyway. So I would think your good. If it does makes 80 psi warm, then check that relief valve under the intake manifold for a shim and remove it. A motor that hasn't been clearanced for racing doesn't need that kind of pressure, chances are you will find its ok after it warms up anyway. The other factor is you don't need a heavy oil either, any 30 weight oil would be thick enough, no need for anything heavier. I am sure there are others that can weigh in with more experience, on the bright side , you apparently have good pressure so thats a positive. Good luck!

[Seth Swoboda]

I just installed a new 221 engine in my '37. It came to me freshly rebuilt, although I had no prior knowledge of the rebuilder. I opened it up and it checked out fine upon my inspection. It has 50 lbs of oil pressure on the gauge at speed down the road. When the oil warms up it holds 30 lbs of pressure at idle. As Ron said, check the relief valve in the valve chamber for a shim. Also remember that the bearing clearances are tight on a fresh engine. I think you will be okay.

[Model51]

Thanks everyone for the advice. It's a standard 1935 engine with no modifications and will be going in my 1935 Demonstrator Truck. I think I'll install it as is, run it for a while before putting the body on and measure oil pressure when running and see what I get. I'll look in the valve galley and check the relief valve and the presence of a shim. Hopefully this will be obvious enough for a novice to spot.

[Ron_r1959]

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Its easy enough, just look to the verry front just above the cam shaft, there will be a plug you can remove with a socket and below it is a spring and a slug with a funny shape ball like end. you will see a indenture of sorts on the ball, this is normal, part of what it does is leak a little oil through a passage to oil the cam gears. Just look for a shim of some sort above the spring in the plug, if it exist, remove it. easy peazy.

[rockfla]

Ronr1959
Any harm in having both pressure relief valves working together...IE an 8ba pump in an 35/36 block. I was told to shim or bush one of them? From your statement one of the two will control the oil pressure over the other, correct??? My block spring does show signs of being shortened. SO I would imagine it would control the pressure??

[69a]

If you have a 80 lb relief on the pump and a 50 lb relief in the block, your engine oil pressure will never go higher than 50. You don't have to change anything!

[tubman]

Originally Posted by 69a

If you have a 80 lb relief on the pump and a 50 lb relief in the block, your engine oil pressure will never go higher than 50. You don't have to change anything!

Finally, a correct reply.

[Mac VP]

The original relief spring was designed to relieve the pressure at 50 psi. They went to an 80 lb spring in 1941 when Ford changed the rear crank seal arrangement from the slinger type to the rope seal type. If the fresh rebuild kept the slinger rear seal, the motor should stay with the 50 lb relief spring. You MIGHT have oil leaking out the back if the pressure is 80 psi and the crank still has the slinger type rear seal. This is easily resolved by changing the relief spring from the 80 lb to the 50 lb spring.

As stated above, the oil pressure will relieve at the point of least resistance, so even if the oil pump (ie 8BA type) has the normal 80 psi relief built into it, the system will relieve at 50 psi if you’ve got the 50 lb spring installed. Both type springs are available.

If the block is the 49-53 type, it is only designed with the rear rope seal (no slinger) so the 80 psi 8BA oil pump will keep the maximum relief at 80 psi. Those blocks never had the pressure relief plug and spring in the oil galley tube, so the relief spring only exists in the pump itself. The 49-53 motors are very content with the 80 psi system.

[Model51]

Thanks for all of the information. I will take the spring out and look at it. The rebuilder of the engine passed, so I can't ask him any questions. Having a 50 psi pressure relief makes sense to me. Somehow I think the 80 psi pump was installed because it was "better". Maybe a bit better oil flow rate, or better pressure at lower engine speed RPM? Regardless, I'd rather not change the oil pump.
I assume there is a way to tell a 50 lb spring from an 80 lb spring? I'll take mine out today, snap a picture and post it.

[vincent]

For what its worth: I have a french flatty with rope seals and the french pump puts out over 90 psi on cold starts. When hot the pressure never dropped below 50 at idle and always 85 when over 1500 revs. Never a problem after more than 5000km. I opened the restriction bore inside the filter container from 1,5mm to 2mm - that only lowered the hot idle pressure to 25 psi. When on the move the gauge still shows 85 psi. Works for me.

[Model51]

Here's the spring from my engine. It's 2 1/2" long including a plug on the end furthest from the retaining nut.
Is this a 50 lb or 80 lb relief spring?
Engine is an original 1935 21-stud motor.

[petehoovie]

Originally Posted by Model51

Here's the spring from my engine. It's 2 1/2" long including a plug on the end furthest from the retaining nut.
Is this a 50 lb or 80 lb relief spring?
Engine is an original 1935 21-stud motor.

[rockfla]

Dave
I can tell you that your's has not been cut. I would bet its a 50 although I don't have mine in front of me to measure.

[Model51]

I see that Dennis Carpenter has an oil pressure spring for 1932-1947 Fords, so I assume that spring is 50 psi rated. Can't tell just from a picture, so hopefully someone will be able to tell from my picture what I've got.
I don't know if the rebuilder changed the spring along with the 80 psi pump or just left the 50 pound spring in place.

[Mart]

Judging from the fact it is a little discolored, that might point to it being unchanged.

Personally I would just run things as is. Run it and monitor it and if you are unhappy with it after a few thousand miles you can always fit a new (or used) 50lb spring.

Mart.

[Model51]

Unless there's higher pressure blowing oil past the mail seal, then it's a much bigger job. I plan to test the engine in the frame and put a pressure gauge in the oil sender port on the engine and see what it indicates.
One more item to add to my checklist!

[FlatheadTed]

I have been running two cars with this combination for 30 x years 34 & 35 Coup both 36 blocks ,on Wed I took the 35 out on a 100 mile run it stayed at about 40 PSI all the way ,Perfect . Only the 34 has a shimmed relief Valve it can go up to 60 PSI cold ,(to much ) , it looes oil ,There was a Bulletin some years back about lowering pressure on the 32s to reduce oil consumption ,I was asked by a 34 Chev owner to investigate severe oil leakage on a 34 Chev previous attempts by Mechanics was to remove the slinger and put a rope seal in ,subsequent repairs refitted another crank with the slinger fitted back on no help .it had 5pis a Idle .Its customary to fit Austin truck big end bearing for the mains with a chamfer along the part line allowing pressure build up to spray out the back I cut a groove with my white metal scrapers on the engine side in the bottom of the Shell with a 8mm galery it has plenty of volume but only 3psi at idle but now no leakage .The 30 psi Ford pump should do the job just fine ,