About oil pressure relief springs- Again

[Bolts]

Been reading all the posts about oil pressure relief springs and plungers and pressure testing of the oil pumps. Thanks everyone for the excellent information. But I'm still a little confused about the whole thing. Sorry to belabor the issue.
First, the engine is a 569AB with an oil pump that has straight gears. I assume it's an 80 pound pressure pump. I opened it up and took out the pressure relief spring and plunger. They were pretty clogged up with 50 year old goo, but are nice and new looking after cleaning.
I opened up the pressure relief housing in the front under the intake manifold and removed the spring and plunger there too. These parts were so rusty and ruined that they have to be replaced.

I cleaned out the oil passages everywhere.

From my reading I understand that the two systems perform the same function and that only one is really mandatory. Yes?

Macs sells a new 80 pound spring. I have read the 50 pounds pumps with helical gears are preferred. I haven't located any 50 pound springs.

So here's my question:
Would it be wise to use two new 80 pound springs from Macs in both the existing pump and the front housing or should I buy a new 50 pound pump? And if so, what do I do about the spring up front in the housing under the intake manifold assuming I can't get a 50 pound spring?

See why I'm confused?

[flatheadmurre]

Straight cut gears would be a 50 pound pump to start with...
And you can make any pump a 50 pound with the correct spring.
Big difference is that the flow is higher with the later longer gears instead of the early ones with short gears.

[Bolts]

OK. Sorry about confusing the issue. I read that helical gear pumps are preferred because they can put out more oil than the straight gear pumps. My mistake in saying the 50 pound pumps with helical gears are preferred. I don't know which are preferred. I guess that's where my confusion starts.

Is it that the helical gear, so called 80 pound pumps, are chosen because they can put out more oil when things heat up and clearances increase and thus maintain a more constant system oil pressure over the engine temperature range?

I remember reading that the 80 pound pumps actually bypass somewhere near 60 pounds pressure. If this is so, when using an 80 pound pump does it matter whether you use a 50 pound spring or 80 pound spring up front in the relief valve under the intake manifold?

I'm trying to figure out which pump to use and which spring to use up in the front bypass valve.

Thanks for your help.

[ckh]

Try All Ford Parts in Campbell, Ca for the springs.

1-800-532-1932

[flatheadmurre]

The big difference is in the height of the gears...you get more flow with a bigger pump/gear.
Straight cut/helical is more about noise/harmonics then flow/pressure in a pump.
Stick in a 80 pound spring in the pump and let the one in the gallery take care of the pressure relief.

[Brian]

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Bear in mind that the rear main and rod journals 4 & 8 are fed directly from the oil pump so could conceivably see different oil pressure than the rest of the engine.

[flatheadmurre]

Originally Posted by Brian

Bear in mind that the rear main and rod journals 4 & 8 are fed directly from the oil pump so could conceivably see different oil pressure than the rest of the engine.

Oil pressure is same in the oiling no matter where the relief valve is.

[Bored&Stroked]

I don't believe the springs are the same in the stock oil pump - versus the stock oil pressure relief spring and plunger in the front of the engine. Anybody know? (I never run the earlier pumps - so I haven't taken one apart).

If the stock pump is good (had good oil pressure) and you're happy with it, you can use it and just replace the spring in the front relief valve.

If you're buying a new pump and want higher oil pressure - here is what I'd do: I'd replace the oil pump with a Ford/Merc 49-53 oil pump (it has the helical gears). You can also get the correct bolt-on pickup from folks like Speedway. This pump will have the 80 lb or so pressure relief valve in it.

Then, you need to update/replace the spring in the front of the block. I don't know if anybody sells a high-pressure (new) spring for the front of the engine - if so, just go ahead and buy one. If not, get a stock spring and stretch it about 3/8" - this isn't exact science by any means, but has worked just fine for me for about 40 years.

If you've gone to all the trouble of pulling the old pump, cleaning up the oil passages, etc - no reason to not put in a new pump.

One question - did you take the whole engine apart before you started cleaning up the oil passages? If not, you've probably loosened up a bunch of crap that will now go through your pump and bearings. Me - I'd only do the cleanup of the galleys if I had the engine apart, was hot-tanking/cleaning it and then was going to put it back together. There is no oil filter on these stock engines - so a lot of crap can be loosened up and then gets pumped through the system.

[JWL]

The later, helical gear pump, is usually "set" at a pressure of 45 to 55 pounds in the "as received" condition. Most are 50-55 lbs. However, that pressure reading does not directly transfer to the oil pressure seen in an engine. Testing the oil pump and verifying relief valve pressure is always a good idea but is simply a way to examine the potential. The clearances leakage varies from engine to engine and has a huge impact on the pressure seen as you drive down the street. It has been my experience the original Ford helical gear pumps are more efficient than aftermarket pumps. A NOS Ford pump should be a prized possession.

The relief valve at the front of the block can have additional spring pressure used to hold it to at least 50 lbs.

The helical gears can provide slightly more volume within the same space(as straight gears) because the face length of each tooth increases with the angle.

[Mac VP]

In the science of hydraulics, pressure will be constant throughout any closed system.....regardless of the distance from the pressure generating source (i.e. the oil pump). If there is a pressure relief opening (controlled by a spring loaded valve) the excess pressure will bleed off through this valve. Since the pump is capable of building more than enough pressure, the relief valve will be constantly bleeding off this pressure as long as the pump is running.

If you have two pressure relief valves, but they have different spring loads, the oil pressure will push against both simultaneously. What will happen is that the oil will bleed off through the lower rated pressure relief valve. The higher loaded spring in the other valve will continue to hold itself closed. So even if you have two or more relief valves, the system will seek its relief through the lowest spring load.....always.

As for our old flathead oil pumps, all the original Ford pumps (1932-47/48) did NOT have a built in pressure relief valve as part of the pump itself. Ford designed the system with a separate relief valve, engineered in the oil gallery line....the tube running from rear to the front in the valve chest. The early V8's had a 50 psi relief spring in there. Beginning in 1941 they changed the spring rating to 80 psi and it received a new part number. At the same time, Ford also changed the oil pressure sender unit to the 80 psi rated unit to match up to the new system rating.

Unless your older (32-48) oil pump is still in good operating condition, you would have to replace them with the latest version pump, which was the 8BA type. You can't buy those older pumps or kits for them anymore. The new style pump has one additional feature....it has its own built-in 80 psi relief valve.

So when you use this pump in the older motors with the separate relief valve up front, you can either remove the spring and plunger from this location, and put the hex plug back in place, or simply leave it all intact. I would change out the spring to the 80 psi type to match up to the 80 psi type in the oil pump.....if your sender unit and gauge are the 80 psi rating. Otherwise I would use the 50 psi spring.

We have both springs in stock. For some reason they are not listed on our website. I will fix that later today.

[flatheadmurre]

Taking the spring and plunger out ??
Wouldn´t that give you free return for the oilflow ??

[G.M.]

Everything is guess work even with a brand new oil pump if you do not
test it. Attached is a oil pump tester I made used by removing the drive
gear and running the pump with a 1/2" drill, the pump rotation is the
same direction as drilling a hole, CW. Use a flexible tube on the output
with a gauge, bend the tube to put a restriction on the pump as would
be provided by the engine. I have never seen any style Ford oil pump
that would not put out at least 80 lbs. If there is a front relief valve the
pump valve should be shimmed with a 3/16" shim to prevent it from
opening. I adjust the front bypass spring to 55 lbs. This can be done by
removing the spark plugs, lubricate the cylinders and place a rag over
to prevent a mess. Install a mechanical gauge in the engine and spin
the engine with 12 volts to the starter with intake manifold removed.
Don't stretch the spring add shims on the top. 1/8" pipe is the correct
diameter for shims. try about a 3/16" thick one to start out, spin the
engine and adjust the thickness to get the pressure you want. The
pressure you have spinning the engine will be what you have driving
at 35 MPH and about. It will be slightly lower as the oil thins from heat.
G.M.

[Bolts]

OK, thanks a lot everyone.
Mac, I think the old pump is good. Believe the engine is 45-48 because of the distributor. Sending unit is not marked, but is probably 80 psi. Gonna go with 80 psi type springs. What part number do I use for those?

B&S, engine is completely apart. Block and all internals and very clean now. I'm being careful about keeping dirt out of the system everywhere. Thanks for the heads up on that.

GM, I was wondering if I might install the pan temporarily, add some oil and crank the starter with a 12v battery to make sure the pump is working and the system oils before closing everything up. Can this be done?

[JWL]

Yes, to flatheadmurre, removing the plunger would open the orifice and provide excellent(excessive) lubrication to the timing gears and a probable reduction in oil pressure.

[G.M.]

Originally Posted by Bolts

OK, thanks a lot everyone.
Mac, I think the old pump is good. Believe the engine is 45-48 because of the distributor. Sending unit is not marked, but is probably 80 psi. Gonna go with 80 psi type springs. What part number do I use for those?

B&S, engine is completely apart. Block and all internals and very clean now. I'm being careful about keeping dirt out of the system everywhere. Thanks for the heads up on that.

GM, I was wondering if I might install the pan temporarily, add some oil and crank the starter with a 12v battery to make sure the pump is working and the system oils before closing everything up. Can this be done?

You can crank with 12 volts to the starter as I described, make sure the
spark plugs are removed and a mechanical gauge installed, don't depend
on the electrical Ford gauge for good results. G.M.

[G.M.]

Originally Posted by JWL

Yes, to flatheadmurre, removing the plunger would open the orifice and provide excellent(excessive) lubrication to the timing gears and a probable reduction in oil pressure.

JWL, That will give you plenty of oil on the timing gears but I think it
will also greatly reduce the amount of oil through the engine?? G.M.

[JWL]

Yes, that was my subtle point.

[40cpe]

"subtle" goes right over most of us. We have to be hit in the head with it.

[Bored&Stroked]

Do not remove the front plunger and spring - just stretch the spring or shim it. That way, you only have one pressure relief valve - located in the later pump housing. You don't want all the oil pressure bleeding out the front to the timing gear (with no spring/plunger).

[G.M.]

Originally Posted by Bored&Stroked

Do not remove the front plunger and spring - just stretch the spring or shim it. That way, you only have one pressure relief valve - located in the later pump housing. You don't want all the oil pressure bleeding out the front to the timing gear (with no spring/plunger).

I think it's better to over shim the pump by pass spring and use the
front valley valve to adjust max oil pressure. This way you don't have
to pull the pan. Also on the pump adjustment you really don't know what
pressure your going to wind up with if you don't have a oil pump tester.
Dumping excess oil on the timing gears go's right into the pan. G.M.