Oil Filter Poser
 

If a stock A engine produces "about" 3 psi of oil pressure .....

How does the oil get through a spin on, full flow filter?

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Uhh ohh. My gauge reads either 10 or 15 psi I think. Maybe that's not a good thing for me. Now I wanna double check to see what's the deal.

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The kit that I bought comes with a brass tube that fits into the discharge hole which makes the oil go through the filter first before exiting into the lifter valley or valve chamber.

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The "A" oil pump, like almost all of them, a constant-displacement design. Normally the pressure is so low only because nothing is resisting the flow of oil. If the oil must be forced through a filter, the pressure will rise. If the filter got all clogged up, the pressure would rise quite a bit.

Doug

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So, the pump is a volume pump, not a pressure pump and the engine is "loose".

That begs the next question.... does the pump have the ability to create enough pressure to open the bypass of the filter? (especially important when starting with cold oil)

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I would say so. I would think Venturis law of blah blah would be the case. X psi building up on one side and being forced through Y size diameter = Z amount of pressure being released on other side.

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The only way to check how much pressure an A pump, or any pump, will produce is to put a gauge at the end of the oil line and not let any oil pass through, like checking fuel pressure. I have heard it can pump 30lbs but don't know how you would check it on a running engine. However, experience from many users shows it will pass through an oil filter no problem. I have pressure to the center main and a full flow filter. My gauge goes over the 10# mark when cold, 0 at slow speed when hot. I used to worry about it, but since the engine has not failed, I don't worry anymore.

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Model A oil pumps are a very conventional design & flows gallons of oil per minute. They have NO pressure regulator valve, thus, the pressure is low. They have great flow to fill the oil chamber & the baffle plate in the pan, as all the lubricating is done by dip or gravity flow. I read that the pump is CAPABLE of something around 80 PSI. With the proper plumbing, they ARE capable of pushing oil through a FULL FLOW filter.
I, personally, have never seen a Model A oil pump fail, or break, except for a failure in the drive gear, & if that happens, you'll know it, as the distributor won't turn & PFFFFT!!!, that sucker is dead in it's DIAMOND TREAD TRACKS!!!!----(CALL A.A.A. @ 1-800-AAA-HELP) Yes, thet's the REAL phone number!
Bill W.

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They are also the same displacement as the early V8 pumps.
Lawrie

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I once tested a rebuilt stock A pump with drill and simple test rig it flowed 10 litres per minute with no restriction at 1200 rpm drill speed
The same pump also made 93 psi when closed off when the drill was not able to keep turning
a stronger drill may have made more psi ???
Colin

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Hi Guy's


The way the A engine oil system is set -up the oil "port" & the center cam brg is the only part of the engine that get's "Pressure"...Some body said the other day if the center cam brg get direct feed from he pump,,,why is it the most worn...???


Greg out West

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Dirty oil ?

CZ:D

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So, for the most part the purpose of the oil pump seems to be to lift the oil to a higher point in the engine so that gravity will pull it down around all the spinning parts. There is no oil pressure because there is no resistance.

Inserting the filter, in this case, would cause a little back pressure on the pump but not change the overall open flow throughout the engine.

Fascinating

Splish Splish Splash I was oiling A bath.....:D

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As Lawrie noted, the same gears were used in the early V-8's roughly '32-35, in a full pressure system. The V8 system was also much more expansive, of course, feeding 6 shaft bearings and four paired full floating rod bearings...the A pump in a stock engine is only asked to move the oil upstairs but is certainly capable of plenty of pressure if channeled properly.
Pressure in an oil system is simply a matter of volume of oil delivered versus volume leaked out of the delivery system.

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Without the plumbing and modifications at the pump for a true pressure feed Model A system, I don't see how that oil pressure would ever open the check valve in an oil filter. I think the filters that spin onto the conversion valve cover may not have the check valve. I would like to know for sure about that.

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FWIW:

I only had one oil pump break over 50 years ago with my Coupe -- it may have been an A oil pump or a B oil pump -- think I still have it -- had it on a B engine w/Police Head marked "B", B carburetor, & B distributor -- the outer cast iron completely sheared off about midway between the pump gears below & the valve chamber above -- heard nothing when it broke; however, not long after, the front connecting rod bearing started knocking "very" loudly -- was traveling a short distance at over 70 mph while drag racing for top speed as a dumb teenager -- had to swap out this almost perfect B engine & replaced it with a very well used oil burning & smoking A engine.

Model A opinions on different subjects are usually different sometimes depending on one's past experiences -- even though Model A & B oil pumps do not break often, because of this one (1) incident, I installed an oil pressure gauge on my later acquired Town Sedan, with a full flow vertical mounted oil filter so I could "see" whether or not oil was constantly flowing -- one oil pump break was enough for me.

At 30 degrees ambient temperature, oil gauge needle is buried "all" the way to the right; however, needle gradually moves left as engine & oil reaches operating temperature -- appears to be functioning properly.

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Mass A man, As mentioned an A pump puts out plenty of pressure. The A system is like a garden hose. water flows out the end with little pressure. Put a nozzle on it and you get a pressurized stream . The oil filter resists the flow like a nozzle and thus there is pressure.

My A pegs the needle at 15lb when cold. the check valve in the filter is of no concern. To answe your question,I think most filters have a check valve. I use Wix and it does.

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On the full floater Ford bearings on '50's OHV engines...many that were close dimensionally were so converted for racing, and Moon supplied equivalent bearings in sizes for the popular engines that were too far dimensionally from Ford flathead...
The reason...the early OHVS when hotrodded could be made to rev far higher than the factories intended...and ran into a rev limit from catastrophic rod failures. Smokey Yunick eventually analyzed this weakness to the behavior of locked rod bearings in rods that distorted their big ends at high RPM's, a type of failure eliminated by the floaters. Rodders soon went a simpler route with boxed or special aluminum rods for drag cars, and the factories eventually strengthened OEM big ends, but for a while many hot engines could not reach their potentials without floaters...
BUT, I mentioned the floaters in connection with the capacity of Model A sized pump gears. Full floating bearings have clearance on both sides, and so offer more area for pressure drop than locked shell bearings...and the little A type gears had plenty of capacity for that.

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Thanks for your reply John. What I was also really wondering, what exactly is BEHIND that spin on oil filter on the valve cover? How does pump oil pressure get restricted to go into the filter on that Model A engine? Some kind of plumbing is needed, I'm sure, but where?