Oil pump pressure test

fredeuce

fredeuce

Member
I am slowly getting the 8BA I am rebuilding to the point where the short motor is complete . Now on to all of the accessories.

Next job is to fit the oil pump.

What I intend to do is make up a sleeve that goes over the main body of the pump to replicate that part of the block where it sits.

The idea is to attach a oil pressure gauge and then crank the pump to ascertain the pressure generated to open the relief valve.

My question is what pressure should be expected with a bench test like this?
 
8BA pumps have an internal relief valve, so if your fixture is set up right (to allow the relief someplace to go), it should max out at factory spec, which is around 55 PSI.
 
fredeuce said:
I am slowly getting the 8BA I am rebuilding to the point where the short motor is complete . Now on to all of the accessories.

Next job is to fit the oil pump.

What I intend to do is make up a sleeve that goes over the main body of the pump to replicate that part of the block where it sits.

The idea is to attach a oil pressure gauge and then crank the pump to ascertain the pressure generated to open the relief valve.

My question is what pressure should be expected with a bench test like this?
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To achieve a proper test the pump needs to be turned at an RPM that reflects what the max engine RPM will be. You will find it takes a good amount of torque to conduct the test. When I test my oil pumps I use my variable speed Bridgeport milling machine. I found using a drill press as the source for testing would not spin the pump fast enough it actually darn near stalled the motor. I always remove the gear so there's a straight shaft to put into the adjustable chuck.

Your design will work fine for testing you will find a lot of oil will be coming out of the shaft/bushing area this creates a heck of a mess. The standard Melling 80 pound pump and the Ford 8BA version in your designed test chamber if in good shape will show 80 pounds on the gauge the relief check valve is set at 80 thus why its called the 80 pound pump.
Ronnieroadster
 
I will admit that I know nothing about Melling high volume flathead pumps as I do not use them. I have to ask why you are stating 80 psi for a standard Ford 8BA pump? I don't have my manuals with me in Florida , but the last time I checked I believe they spec'd 55 psi for a stock Ford at highway speeds. Also, the last two engines I built with stock Ford pumps and new relief springs also ran at 55 psi. The oil pressure gauge in Ford cars using the 8BA engine all are 80 psi maximum gauges. I have never seen one that runs down the highway with the oil gauge constantly pegged.

I am talking stock or mildly modified engines here, not all-out racing units.
 
tubman said:
I will admit that I know nothing about Melling high volume flathead pumps as I do not use them. I have to ask why you are stating 80 psi for a standard Ford 8BA pump? I don't have my manuals with me in Florida , but the last time I checked I believe they spec'd 55 psi for a stock Ford at highway speeds. Also, the last two engines I built with stock Ford pumps and new relief springs also ran at 55 psi. The oil pressure gauge in Ford cars using the 8BA engine all are 80 psi maximum gauges. I have never seen one that runs down the highway with the oil gauge constantly pegged.

I am talking stock or mildly modified engines here, not all-out racing units.
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Well I will be happy to explain. The pumps I referenced are NOT the high volume pump that Melling offers that some use for racing. The high volume Melling pump will put out 100 or more PSI easily when testing.

The numbers I reference in my post are the Standard production Ford and Melling replacement pumps. Many stock newly build flatheads with the standard Melling or Ford pump register higher than the 55 pounds you referencing to at highway speeds. When I test pumps I find the numbers to be high as I wrote above. Its expected when the engine oil get warm the readings go down plus the weight oil used will also dramatically effect the readings.

I use a very powerful and accurate rotating source by which I can control the actual RPM. The test chamber I use is showing the true pressure of course there will be variations of results. Using a mechanical gauge will not register fast enough to show when the relief is opening. Not sure you know this the oil pump relief design is returning the oil directly into the inlet side of the pump gears its not bleeding excess flow/pressure back into the pan.
I'm posting what I find nothing more and nothing less. Thanks for asking.
Ronnieroadster
 
My testing shows little difference in pressure after the relief valve opens when using 10W oil at various RPM. All Ford pumps, I have tested, begin relief opening at 52 to 55 lbs. In my testing the replacement pumps are generally less efficient than FoMoCo pumps. My sample size is less than 50 and more than 25.
 
JWL said:
My testing shows little difference in pressure after the relief valve opens when using 10W oil at various RPM. All Ford pumps, I have tested, begin relief opening at 52 to 55 lbs. In my testing the replacement pumps are generally less efficient than FoMoCo pumps. My sample size is less than 50 and more than 25.
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Although my sample size is smaller (5), this is what I have found as well. My experience with non-Ford pumps is also similar. I put a regular pump from Speedway Motors in my latest rebuild because, well, it was new. It barely put out 40 psi on the gauge. This didn't seem right, so I replaced it with a stock pump that I had checked by a reputable engine builder on this forum. It came back from him with a new spring and a tag on it that said 57 psi. I installed it in the engine, which now reads 57 psi at 3000 rpm.
 
I have tested many pumps in my test stand. I turn the pump with a 1/2" drill motor at about 1100 rpm. Pumps show relief numbers just like JWL has indicated. I installed a ball valve on the outlet and close it down to measure relief pressure. I can also measure flow rate at any outlet pressure. I usually measure at 40 psi. restriction.
 
10W oil used for testing well there's a big difference there compared to the weight I'm using. Not many fellows in these parts using 10w oil in there flathead engines that I know of.
Ronnieroadster
 
I use 10W - 30 for testing. This is the weight oil I have been using in my engines for many years.
 
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tubman said:
Although my sample size is smaller (5), this is what I have found as well. My experience with non-Ford pumps is also similar. I put a regular pump from Speedway Motors in my latest rebuild because, well, it was new. It barely put out 40 psi on the gauge. This didn't seem right, so I replaced it with a stock pump that I had checked by a reputable engine builder on this forum. It came back from him with a new spring and a tag on it that said 57 psi. I installed it in the engine, which now reads 57 psi at 3000 rpm.
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Caution Speedway pumps are from China you get what you pay for.
 
Ronnieroadster said:
Caution Speedway pumps are from China you get what you pay for.
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Yep; I found that out the hard way. It was a useful exercise though. First, run a fresh rebuild with the Speedway pump and barely get 40 psi at speed. Then replace it with a tested, known good Ford pump and get 57?

I can't think of a better comparison than that.
 
I have found that 10W30 will hold 25 psi hot idle and 55 psi going down the road in a properly rebuilt stock engine.
 
I believe that the O/P's original question has been lost in a discussion that, to me, boils down to the difference between a good stock rebuild and an all-out racing engine.

Assuming the O/P is doing a stock (or close to it) rebuild, I still say 55 psi is the number to shoot for.. My mid-fifties "Motors Repair Manual" says 50-55 psi. There are others who seem to be in the same camp.
 
I’ve always admired Ronnie and these other guys that build the truly bad Flatheads .
I’m certain it takes knowledge that I will never have .
These guys engines have clearances,,and performance parts I can never attain,,,,way out of my league .

But,, for a stock,,or mild performance,,,or even hot street engine,,,,the Motors Manual information is what I go by .
It fits my application very well .

Tommy
 
I conducted the test this afternoon by setting it up in the drill press on the slowest speed and using 10-30W oil. Once the air was out the needle belted the peg on the gauge quite hard . It is a 60 psi gauge. I think we are good to install it now and see how it performs on the running engine.
 
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