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#1 |
Senior Member
Join Date: May 2010
Location: Eastern Tennessee
Posts: 11,972
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I was thinking this morning about what the advantages and disadvantages of using a Model-B Oil Pump Shaft (the one that is machined smaller between the two bushings) in a Model-A oil pump application. I know my Dad was a big believer in doing this however I am curious on others thoughts with this. If a little is good, is more better??
![]() My initial thoughts on this now is I don't believe it is of value in any method on an A engine, but maybe I am wrong. My reasoning is the dipper tray should already have engine oil remaining after the last time the engine ran. Even the wells inside of the valve chamber area should have oil remaining however in the event it doesn't because the engine has sat for an extended period, the engine will likely crank over 6-8, maybe even a dozen times before it starts. The length of time it takes for the good oil pump to begin filling the chamber is about 2-3 revolutions. Someday I may cut a valve cover and see how long it takes to fill the entire chamber area, but I my guess is 2-3 dozen revolutions of the crankshaft will have it full, and even less revolutions will have oil already flowing thru all 3 drain tubes. So the next thought is why do we need the extra volume of oil being moved by the B shaft? In a pressurized application, I think there is a cooling effect that goes with the extra volume, but in the A application, it is only going to fill the chamber, ...and from there it will either fill the side tube or spill over dam behind the timing gear. As such, does the extra amount of oil create windage for the crankshaft, -and/or does the extra volume of oil create loss of Hp or addition stress on the oil pump drive gear or cam gear? Thoughts or opinions??? . |
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#2 |
Senior Member
Join Date: May 2010
Location: Oregon
Posts: 1,462
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Brent's thoughts about the adequacy of flow from an A pump are correct. Even a worn pump will have sufficient output for a stock motor. The first Model A engines lacked the oil return tube and Ford added it to handle the flood of oil in the galley. Later efforts by engine rebuilders to address this involved hammering out part of the dam on the forward end of the galley. Note also that the Model B engine dealt with the flood by drilling two 3/4 inch holes in the floor of the galley, from whence it drops straight to the dipper tray, fore and aft. This lowering of the oil level also has the benefit of reducing oil lost up the valve guides, which was further addressed in later Ford V-8 engines by use of valve guide seals.
A few years ago somebody posted pictures and a description of their experiments with the A oil pump. This fellow made a Plexiglass valve chamber cover so that the inner workings could be observed in real time operation. The stock A pump produces quite a deluge of oil in the chamber and does it quickly upon start-up. The B shaft is only useful in the event that one has the early Model A forged oil pump casting with the narrowed passage vane. Unfortunately, they are hard to find, as the Model B guys will tell you. |
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#3 |
Senior Member
Join Date: May 2010
Location: Cen~Col - Central Highlands
Posts: 2,757
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Last edited by Benson; 10-07-2017 at 11:18 AM. |
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#4 |
Senior Member
Join Date: May 2010
Location: Oregon
Posts: 1,462
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The B-pump was also intended to supply pressure to the mains, as gravity flow was thought insufficient to lubricate and cool the larger 2-inch main journals.
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#5 |
Senior Member
Join Date: May 2010
Posts: 532
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My thoughts:
1) I always thought an oil pump is a "positive displacement" pump (more like a vane pump used in some A/C compressors vs. centrifugal pump like a water pump). Thus, the amount of oil pumped is a function of the clearance between the drive gear and idler gear teeth, and between the housing and the gears, and not so much what restrictions are downstream. So the oil volume doesn't much depend on the downstream shape of the pump drive shaft, but pressure would be impacted by downstream config. But as the clearances open up as wear occurs, maybe the pump is just imparting kinetic energy like a centrifugal pump. Just my thoughts on "science" 2) I rebuilt my A pump with a Bratton's kit (straight shaft as I recall) and it took over 2 minutes to get oil out of the oil return tube. Scared the heck out of me so I replaced the pump with a new one. Had oil coming out in about 20 seconds 3) I made a handy tool to see and time oil flow for start-up... took an old oil return tube and cut a section out of it. Went to Home Depot and bough some 3/4" ID clear tubing and hose clamps. With a clear section in the oil return tube, I could easily see when oil flow was established without the mess. Thanks for listening... |
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#6 |
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Join Date: May 2010
Location: Mpls, MN
Posts: 27,582
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#7 |
Senior Member
Join Date: May 2010
Location: Camino, CA.
Posts: 3,086
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My deluxe delivery has a somewhat modified model B engine with what looks to me like a V8 pump. It doesn't reach the bottom of the oil pan. I added some dams in the pan to keep the oil from flowing away from the pump on sharp turns or fast starts.
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