oil pump shield

Jim Huseby

Jim Huseby

Senior Member
For the EXPERIENCED to answer/comment: Have you observed any evidence that the oil pump shield restricts adequate oil return to the sump, partially starving the pump and/or resulting in throwing excessive oil out the filler tube? This question relates to my musing as to how much oil is in suspension above the dip tray in what is a violent storm of oil and what level of oil the pump's pick-up port is submerged in (or not) at cruising speed and even at idle. Since the late A's and the B's used the shield and the B's pump needed to supply non-aerated oil under slight pressure, I assume there is adequate drainage to the sump. The shield's purpose was to keep the oil above the dip tray from returning to the sump around the pump clearance arc to help keep from starving #3 and #4 rods, but what have you observed or measured (or considered) from experience? I haven't given this enough thought... The crank and rods are throwing the oil upward on the right side of the crank case wall and downward on the left side...this is on an A engine with pressure to the mains only and the same volume as stock to the valve chamber and dip tray.
 
Hi Jim,

In trying to seriously answer, "For the EXPERIENCED to answer/comment:" question, this has been my own personal experience.

If we look at Ford's 1920's 1930's results coming from Ford's professional engineers, his factory workers, his dealership mechanics and the like, Ford had a wonderful record of vintage engineering improvements from the Model T, throughout Model A production, and into development of the Model B.

By the time the Model B (4) cylinder came about, we saw a centrifugally advanced distributor, a higher compression head, more lift on cam lobes, lightened flywheel, more oil flow in oil pump, synchronized transmission gears, more efficient carburetor, larger opening in intake manifold, fuel pump with gas tank in the rear, softer riding tires, larger brake drums, etc., etc.

Maybe Ford engineers never had a plexiglass oil pan with a built-in slow motion camera to monitor oil molecules; however, with Ford's past improvement records, the oil pump shield seems like it originated with his same production advisers to better the finished product ....... consequently, I installed one in my last rebuild.

But ......... just one opinion, from past experiences.
 
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When you fill an engine after a rebuild, the oil goes into the dipper tray first and overflows into the sump. The tray cannot be overfilled, excess goes into the sump. It's the law!
 
I recall some Ford documents stating that the purpose of the shield was to improve the distribution of oil throughout the dipper tray. The Model B engine had no oil return tube like the Model A, drainage holes punched into the upper rails of the dipper tray, and drainage holes in the floor of the valve chamber. It seems that all of this was intended to result in a better overall distribution of oil throughout the engine although I haven't seen any evidence that the B-engine had a longer life than the A-engine.
 
There is one pressure fed bearing on the A, the center cam bearing, the oil pump shield directs "leakage" from that bearing onto the dipper tray, if the clearance there is at .005 the "hole" is the same area as the outlet pipe in the valve chamber---so in theroy 1/2 of the oil pumped could leak there ----the next evolution was some holes drilled at the edge of the tray to keep the tray from being overfilled----perhaps for when on downhill inclines where the tray could get overfilled and splash too much----
 
Thank you for the thoughtful answers. I agree that the shield had to be an improvement, as they appeared on the late A's and through the B production. But if you set a pan with an A dip tray in it on your work bench and hold the shield in place, you will see the shield covers a large area where oil can return from the tray to the sump. I have not looked at factory illustrations or specs on possible dip tray changes that accompanied the appearance of the shield and I have no assurance that the trays in my B's were not replaced with earlier ones at some time. I had a B tray that had the end flanges cut down, but hadn't considered why at the time, and I just found another one. I'll look at some more and see if there are various designs. Ursus and Kurt in NJ report that the B trays were modified for additional drainage and that greatly helps answer my question.
 
"Never" a bad idea to always be extremely cautious "if" trying ..... and/or "if" using ... anything Model A "Used" ......... or anything Mode B "Used" ..... on a nice vintage car.

ASSuredly, the DARWIN AWARDS of trying things in the 1930's were not much different than that of those today in 2017.
 
H.L.C.- Thanks for posting the cautionary note! Many or possibly most of us (which, I assume includes you, because all the advice you have given us had to have come from research and the experience which carries a certain amount of risk), after all the caution and research and testing the water and minimizing risk, sooner or later take the plunge gun ho and risk mortal embarrassment. The comments on this thread have saved me from having to spend more hours researching; a great benefit.
 
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