8BA Oil Pump in a 21 Stud...What is involved? Need some guidance.

[phartman]

I am not happy with the low oil pressure in my '36LB on really hot days. I plan on replacing the bypass spring (and possibly shimming it), but am curious about the upgrading of the pump to the 8BA unit.

Anybody done this conversion? Anybody able to walk me through what is involved? Thanks.

Pete

[Bruce Lancaster]

Generally the '49 pickup pickup (!?) is about right depth...check this with modeling clay impression, you want lower edge maybe 3/8 or not too far from there off the floor. Early pans have a variety of baffles, vertical plates, that will get in the way...tin snip time if you encounter this. Gear, upper mounting are fine. Ron and Vergil encountered serious issues with current new pumps, so check gear clearances and endplay and also fit of casting into block AND seating of the plunger...one pump reported had badly machined plunger that dumped all oil pressure at the source!
Naturally, checking out the essentials voids your guaranty but better to toss a pump than an engine.
After corresponding with someone de-bugging a new M pump that produced nearly no pressure, I dug all my old cores out from under the bench. The ones I checked had correct clearances as found in the junkyard, and new bushings are easy...

[JM 35 Sedan]

Pete, I put an 8ba oil pump in a '35 poured babbitt engine. It was a mellings M19. You will also need to use a pickup tube and screen that's made for a truck engine/oil pan. Several venders list this combination in their catalogs.

[phartman]

Bruce, John, here is what I'm not fully understanding. Is there any reason that the original style pump can't produce the 50 psi that I'm after? If I have a correctly rebuilt pump and the correct tension on the bypass spring, why not call it a day?

Or another way to put it, is there an advantage that the Mellings M19 or that style pump gives me that the original does not?

I see that Dennis Carpenter, for instance, sells a 50 psi version and an 80 psi version of the '36-'48 pump.

What particular advantage does the 8BA pump give me?

Thank you for the help here, guys.

[Bruce Lancaster]

Pressure in oil system is a product of volume, how much is pumped into the galleries versus how much comes out around the edges of the bearings in a given amount of time. In a tight system an early pump should be fine.
There are 2 8BA pumps...first one, used during 1949, is somewhat uncommon now and has straight-cut gears, later one has -B in casting and spiral gears. This became very common in rebuilds of earlier engines because of availabbility, somewhat higher volume, and is I think as reproduced by Melling the only common new one now.
Pressure spring is a relief that dumps oil out of the pressure system if it gets too high, and has no influence on pressure below its relief point...
What is low on your engine? What weight of oil?

[phartman]

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Bruce, first let me qualify things by saying I am running an electric oil pressure gauge and not a mechanical gauge, so it could be the gauge that is off. Could be a false reading.

I tried deliberately to put the motor under stressful conditions over the weekend. It was well into the 90s here in Richmond with very high humidity. I ran the truck around town under stop and go conditions. As a sidenote, it is intersting to me that whether I ran the truck with the hood on, or off, the motor coolant temperature ended up being about the same. You'd have thought it would run cooler without the hood, but that was not what I observed.

The radiator never puked, but the water temp was hovering right at 200 degrees. The very best oil pressure I got at speed with the motor hot was a 20 lbs or so, and at idle it dropped to 5 pounds or less. The motor does not have any ticking or knocks to it. But that pressure seems pretty low to me.

I am running 20-50 oil. At least one person suggested running straight 30 wt, but that doesn't seem like it will make much difference.

[OLD...BILL]

PETE: We need more info, IE, real oil pressure, new / or better gage, are you running
Heneys oil filter, with restricker fitting ?? How many miles on enegine (about )...at this point I would shim the oil bypass spring, with two or three washers, on the check valve, more spring pressure. and run it.. and get back to us. ... OLD...BILL

[phartman]

Bill, rebuilt motor with less than 5,000 miles on it. Runs like a champ, no funny noises or knocks. I didn't do the rebuild- the prior owner did- but from the receipts he kept, he used quality components. From the markings on the crank and other evidence, whoever did the motor rebuild knew what they were doing. No oil filter or restictor fittings.

First step is to hook up a mechanical gauge and get the true oil pressure. And, yes, we were going to replace the spring and possibly shim it on the bypass valve as well, if need be.

But we're still back to my original question: Is there anything inherently superior to the 8ba pump that I can't achieve with the stock pump if what I'm looking for is 50 lbs of oil pressure? If I replace what I have with a properly rebuilt stock pump, what am I gaining by using the 8ba pump? If my stock pump is rebuilt properly, is it adequate for a non-racing application?

Thanks again, guys. Your guidance is always appreciated.

[bobH]

I'm puzzled... 20 at highway speeds, 5 (or even zero) at idle... sounds good to me.

[phartman]

I'm thinking on a '36LB the numbers should be more like 10 at idle and 30+ at speed. Correct? What I'm reading on my motor is ok? Seems low.

[OLD...BILL]

PETE; There are meany answers to your question, why did Ford go to, or build the 80 lb pump. the engines were getting bigger and so where the cars. and add in the automatic trans. more torque and more RPMs just to get it to move,,,no not a good answer to you question, but for all the years that 50 lb.pump worked for us so well. YES you should have better pressure than 5 at idel, and 20 at 30 mph. Lets see what you get with the new gage and new spring / shimed,,, new reading ?? JM 35 are you going to jump back in here ....OLD,,,BILL

[Brian]

Sounds good to me, however, is the oil pressure sender unit rated at 50 or 80 lb's? Using an 80 lb sender unit with the 36 [50lb] gauge will cause the gauge to register lower oil pressure.

To answer your other question; 8BA gears are helical, longer and bigger dia than early gears. Accordingly, for each revolution they will push more oil than will the early, by virtue of the increased surface area. The relief valve controls the maximum pressure, so, if you had two pumps, one early, one late, and the relief valves were set on both pumps @ 50lb, both pumps would maintain a maximum oil pressure of 50 lbs, however, the 8BA, by virtue of it passing more oil/rev will obviously show a higher pressure than the other if the relief valve is not open, eg, at idle, [all other factors being the same]. Hope this makes sense.

I still maintain that there is nothing wrong with the pressures you're reading on your gauge for a 21 stud motor. Brian

[phartman]

Brian, you know, I have no idea which sender it is. You have a great point there. I'll need to check. That very well could be the answer.

[Bruce Lancaster]

When you get it out, I believe the 80 senders have the 80 stamped down on the brass fitting area. For now, I would bypass that issue and go straight to a mechanical gauge temporarily...no need to really install it beyond the 1/4 block fitting, just run it out the hood to where you can see it. Get some real numbers before you try to analyze, also good practice so you know what the marks on the stock gauge actually mean for when you go back to stock.
Present numbers are low but adequate, nowhere near scary.
Assuming nothing odd like a weak relief spring more volume in via the late pump should boost the pressure.
Unless you find and build an original 8BA-B pay close attention to casting fit, side and end clearance, and fit of the relief plunger. New pumps have been found with definite problems in all those areas resulting in very low pressure on good engines...as I said, I now regard my little bin of junk -B pumps I purchased for their Merc or Truck pickups as likely cores for reuse.
There also exists a higher volume Melling...I think this generation uses Chevy gears, but not sure.
JWL and others have posted test procedures for pumps, one I think involving running pump deadheaded with gauge, another running starter on 12V to get pump into its working range. Good ideas to avoid extra teardown...