Technical 8BA low oil pressure/restrictor fitting

I have a 1950 Ford coupe for ten years and have put about a thousand miles on it. I was told by the PO that he rebuilt it and it was punch out .80 over. It has headers and has always ran well. I noticed when I first bought the car it had low oil pressure according to the stock gauge. I replaced the oil sending unit shortly after I bought the car thinking it was faulty. No change only 10-20 lbs. The oil sending unit is mounted up by the oil filter can on a brass T fitting (not stock) and I thought the low oil pressure reading was caused because the oil sending unit was installed behind the restrictor fitting or no restrictor fitting at all. I took the T fitting off expecting (hoping) that was what was causing my low oil pressure reading. Easy fix. The brass fitting is screwed directly into the oil filter can. The other end is connected to the oil line coming from the back of the engine with the sending unit in the middle. I don't know what size the hole is yet, but it is smaller than .80. I am going to buy some smaller drill bits to see what size the restrictor hole actually is. After seeing the fitting, I am thinking the engine is missing oil galley plug(s). Can I get to the plugs without pulling the engine? Who sells this fitting? Thanks in advance.

 

The restrictor should be .060, or 1/16" . your set up with the T is how they did it on 8ba's. If the galley plugs were out I think you'd have no oil pressure ! Flatheads don't need a lot, they will live a long life with low pressure. You could fool with the relief valve, but that means removing the oil pan. I'd just drive it myself.

 

10-20 PSI doesn’t sound bad for a flathead to me.

 

Thanks. The guy I bought the car from told me not to worry about low oil pressure. He is 85 years old now. He told me if it bothered me that much to put a piece of black tape over the gauge! I think I will put this back together and call it good. If anyone has this fitting, or knows where to get one, I would like to buy it. Thanks again.

 

Weatherhead makes them. I get them from NAPA or any of the online early Ford suppliers should have them

 

Just so everyone is aware. My 1953 Motor's Auto Repair Manual (the big blue one) lists the normal oil pressure for the 8BA series of V8's to be 57 psi. This is at speed, not idle and I believe it to be correct, as this is just about what I have at 2000 RPM on the fresh flathead that I just built. The engine idles at 25 psi.

I know they'll run at less, but the Ford engineers set them up to run at that pressure for a reason.

 

The factory gauges of that era are not very accurate. More of an indicator....
hook up a good mechanical gauge, you might be surprised at how much oil pressure you have
My 8ba has about 30k miles on it now, still has 45 psi hot cruise rpm, 20 at hot idle

 

Tubman is correct. The 8BA should have lots of pressure. The restrictor fitting on the filter can is not available, to my knowledge. You have to make your own. .060" hole is a little large for my liking. A tweek smaller is what I like. To make your own restrictor fitting, thoroughly clean and flux the hole in a standard flare fitting, stand it on the threaded end, heat and melt a little solder down the hole. Try not to get solder on the flare. It will cause a leak. Drill the new hole to your liking all the way through the solder. Make sure no chips are left in the hole. Put it together and you're good to go. If you have the correct oil pump, you should expect 40- 50 lbs of pressure, more or less at hot street speed and around 20 to 30 lbs at idle with 10-W-30 oil.

 

Weatherhead 1512. Carpenter and others list a restrictor fitting for a N series tractor for less than 4 bucks. Not sure if its the same or not. One for a flathead on eBay but pricey at almost 30 bucks. Probably the solder and .060 drill method would be the fastest solution.

 

Thanks for the replies. I am going to find out today what size the hole is. I have two other 8ba engines and they both have a restrictor fitting that the oil line coming up from the back of the engine connects to that is screwed into the oil filter can. The oil pressure sending unit is screwed into a threaded hole in the back of the block. I am going to get a mechanical oil pressure gauge and see what it says. I would be very happy if it was just the oil pressure gauge. I filled a fitting with solder last fall but have not drilled it out yet.

 

"I filled a fitting with solder last fall but have not drilled it out yet." Then it's time to get the lead out!

 

That's funny-made me laugh! Anyway, the small hole in the end of the fitting is .060. I bought a mechanical oil gauge set-up at O'Reilly's and plan on installing it tonight. Stay tuned!

 

Let me get this straight. If you're running an oil filter on the 8ba motor you need this restrictor in line? As mine does not have it and I haven't fired it up yet

 

Yes, if you don't have a restrictor fitting on the line going to the oil filter housing you will not have much oil pressure. That's my understanding for the restrictor fitting. Hopefully other hambers will chime in to verify this. P.S. The fitting I posted is different than the ones I have seen for sale on E-bay. It's just a fitting that screws into the oil filter can that the line connects to. The fitting I have is a T fitting to connect the oil pressure sending unit to it. I have normally seen the oil pressure sending unit screwed into the back side of the block. This T fitting makes it a lot easier to get to the oil pressure sending unit.

 

Maybe I don't understand this, but the oil filter on a flathead is a by-pass filter. That means you are taking some of the oil from the engine and running it through the filter. It is my understanding that the restricted fitting is there so that you don't lose too much pressure through the filter. You are limiting the amount going through the filter in essence to keep the engine oil pressure in the engine from dropping too much. If your gauge sender is connect past this restriction you really aren't reading the engine oil pressure. The gauge should be "T ed" in before the restriction. The filter I added to my 47 Ford had the restriction at the inlet of the filter housing.

 

Yes, you need the restrictor when using the original type bypass system. It keeps pressure high in the motor, and low in the filter housing so the lid doesnt leak. The OP's T has the restrictor in the port to the filter, so upstream port for the sender is fine, and the other is of coarse the line in from the block

 

Thanks. the last two posts explain the purpose of the restrictor fitting. Probably wouldn't be good to have 50-60 lbs. of pressure in the oil filter can. I think you would have to over tighten the bolt to keep from blowing out the rubber seal.

 

Tonight, I installed a mechanical gauge and at cold idle about 20lbs and hot idle 11lbs. At 3000 rpm cold about 39lbs and 28lbs hot. The oil is Valvoline VR1 20-W50 high zinc racing oil. Would installing a new oil pump possibly fix the low oil pressure? Any thoughts? Thanks again.

 

Well I guess I need to get a restrictor as this setup never had it for some reason

 

You know there is a truck or heavy duty oil pump with taller gears, maybe that would help.

 

I have always stuck to this one oil pressure fact/the claim is 10 lbs pressure for every 1,000 rpm is acceptable for a flathead v8—meaning 2,500 rpm should equate to at least 25 lbs pressure. Flatheads don’t have to have a lot of oil pressure to survive and take you down the road. Flatheads Forever!!

 

10 lbs for each 1000 rpm is pretty standard, up to whatever the engineers deemed necessary. Buick for many years said "35 lbs at 35 MPH" which is lower than 3500 rpm. So different manufactures had different goals, I guess.
I don't worry unless it CHANGES drastically.

Ben

 

I began using Lucas 20w-50 racing oil last year on my rebuilt 59L engine.
The engine always showed minimal oil pressure on my stock gauge with Valvoline 20w-50 VR1
As soon as I installed the Lucas oil my pressure increased 15 lbs .

 

Thanks, I am changing my oil this weekend and I will give it a try.

 

There's a very good thread, "Full Flow Flathead Question" posted by @douglasb , Feb. 17, 2022, that covers this. I couldn't find a way to link the thread onto here.

 

You’re only partially correct. Without the restrict or, you essentially have a leak path from the oil pump back to the crankcase on an engine with a bypass filter.

Full flow systems return oil to the pressurized gallery, so oil pressure is a function of bearing clearance except at high engine speed where the bypass valve takes over.

Leakage at the filter housing lid isn’t a real consideration when designing these systems.

put the gauge before the orifice, or it’s not reading gallery pressure.

Pressure in the hydrostatic wedge in a journal bearing is something like 40000 psi, and is what maintains metal to metal separation,****uming proper clearances. High bearing clearances increase flow requirements to the point that the oil pump can’t keep up. Gallery pressure has a relatively minor effect on actual film pressure at the bearings, but you certainly don’t want to run without pressure. 10 psi at idle and 10 psi/1000 rpm is a general rule of thumb.

 

After looking it up online to buy one and seeing the picture I went and checked my canister and sure enough I already have one installed

 

That looks like the correct restrictor fitting. hamber 51504bat shows the part # as weatherhead 1512. Ebay sells them also. I bought some (5 qt. bottle) of Lucas hot rod and classic car oil 20w-50 high zinc from Amazon tonight. I will post the readings between the Valvoline 20w-50 and Lucas 20w-50 later next week. Glad to hear you verified that you have the restrictor fitting in place wheeltramp brian.

 

Please let us know of your results.
Good luck.

 

I finally changed the oil in my 8ba. The pics represent the oil pressure with Valvoline VR1 20W-50 racing oil in this order. cold idle-Apprx. 500rpm, cold at apprx.2500rpm, hot idle, and hot at apprx.2500rpm. With Lucas classic car 20W-50 oil pressure readings are as follows. Cold idle-apprx. 500 rpm, cold at appx. 2500rpm, hot idle, and hot at apprx 2500rpm. all readings were taken after running for apprx 25 seconds for each picture. Hope this makes sense.