Pressurized center main bearing?

[mcgarrett]

Watching one of the Hagerty Model A engine rebuild videos, they show adding a copper oil line to the center main cap but didn't go into any of the details on how to plumb it up to the oil pump. What would be the reason for doing so?
Anyone ever done it to their engine? How does it connect to the oil pump? I'm interested in knowing more about this process.

[Bob C]

See this link. http://www.modelaparts.net/special.h...entermain.html

[Jim Brierley]

I drill and tap a 1/8" pipe thread to the pump body and run a 3/16" tube to the main as shown in the link above.

[mcgarrett]

Bob C. & Jim B.
Thanks for the excellent information. I wasn't aware of this modification. Just so happens, I am installing a counterweighted crank so this information is most welcome!

Jim, where on the oil pump do you drill and tap for the brass fitting?

[oldspert]

Originally Posted by Jim Brierley

I drill and tap a 1/8" pipe thread to the pump body and run a 3/16" tube to the main as shown in the link above.

The link does not show to tap into the pump body, but to tap into the oil galley and run a tube to the center main bearing cap. Is there an oil pressure area under the lifter galley similar to when adding an oil filter?

[Synchro909]

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I have posted here many times till some of you must be tired of hearing about how I drive long distances in my Model A while towing. The motor is working hard all day every day for weeks on end. Like you, I have installed a counterweighted crankshaft and I pressurised the middle main bearing. I tapped the oil pump housing just below the sump (pan) rail and restricted the oil outlet at the top of the pump which I modified like a B pump. I ran a short 1/4" copper line across to the bearing cap which was drilled and an elbow installed facing the oil pump. At a convenient place along that 1/4" pipe, I put a Tee with the right angled leg facing down. I made and screwed a pressure relief valve there but had to cut a hole in the side of the dipper tray to accommodate it. The valve regulated the pressure to a max of 25-6 psi. The relief valve points downwards to avoid the counterweights on the crankshaft. I tapped the top of the hole in the valve chamber where the oil used to run down to that bearing and plugged it.
I can be a bit of a fiddle to fit the pipe because it is so short but it can be (and has been) done.
BTW, I run insert bearings and an oil filter in the motor. The whole motor is getting a bit lose now but after 70,000 miles including about 50-60 thousand done while towing at 50 mph, I'm not complaining.

[mcgarrett]

Synchro909,
Thanks for adding more clarification to this subject. If you have a moment, take a look at the link in post #2. Do you have any idea where the fitting and tube installed on the pan rail near the oil pump hole connects to? I looked at my block on the engine stand and I can't see where it would pick up any oil pressure from the pump. I don't understand what this would accomplish. Maybe someone else here on the Barn has seen this and could reply.

[Synchro909]

Originally Posted by mcgarrett

Synchro909,
Thanks for adding more clarification to this subject. If you have a moment, take a look at the link in post #2. Do you have any idea where the fitting and tube installed on the pan rail near the oil pump hole connects to? I looked at my block on the engine stand and I can't see where it would pick up any oil pressure from the pump. I don't understand what this would accomplish. Maybe someone else here on the Barn has seen this and could reply.

A pleasure! I can't see where the oil pressure would come from in that picture. Maybe we heed to see another angle or better still, the engine. Maybe someone else can fill in this gap.

[johnneilson]

It sounds like the oil passage in a B model

[Synchro909]

Originally Posted by johnneilson

It sounds like the oil passage in a B model

Maybe but who would want to go to all that work when the main bearings in a B engine are already pressure fed?

[mcgarrett]

Appreciate all the responses. I still need to know for sure exactly where to drill and tap the oil pump body for the oil line. I hesitate to move forward with this modification until I'm sure about that.

[johnneilson]

Originally Posted by Synchro909

Maybe but who would want to go to all that work when the main bearings in a B engine are already pressure fed?

I have no idea, none of this makes sense.
Oh, and just to clarify, the mod B is not pressure fed, only directed oil to the bearings. It can be modified to pressurize.

J

[Jim Brierley]

Syncro, you restrict the outlet of the pump??? Sounds like that is defeating the purpose of it all except the center main.

[Joe K]

Originally Posted by Jim Brierley

Syncro, you restrict the outlet of the pump??? Sounds like that is defeating the purpose of it all except the center main.

Maybe oil flow goes "back" in the traditional center main oil gallery thus feeding the valve chamber, and from hence everywhere else in the normal path?

I had to think about that as a possibility...

The Model A oil pump is generally considered to "not have much pressure." I've read somewhere less than 3psi. Which - without augmentation - is not enough to effect "hydrodynamic separation" of the bearing moving parts in the traditional insert bearing mode.

Or perhaps "positive" lubrication is more the goal rather than actual hydrodynamic separation?

My brother, who was into drag racing, told of dragster augmented oil pressure actually "blowing out" bearing inserts - 5000 rpm can do that I guess.

Joe K

[BRENT in 10-uh-C]

Originally Posted by Joe K

Maybe oil flow goes "back" in the traditional center main oil gallery thus feeding the valve chamber, and from hence everywhere else in the normal path?

I had to think about that as a possibility...

The Model A oil pump is generally considered to "not have much pressure." I've read somewhere less than 3psi. Which - without augmentation - is not enough to effect "hydrodynamic separation" of the bearing moving parts in the traditional insert bearing mode.

Or perhaps "positive" lubrication is more the goal rather than actual hydrodynamic separation?

My brother, who was into drag racing, told of dragster augmented oil pressure actually "blowing out" bearing inserts - 5000 rpm can do that I guess.

Joe K

A stock Model-A oil pump can peg an 80# oil pressure gauge when the system is capped. ( I know this from firsthand experience with my old race car. ) The same thing with a garden variety water hose. Without a nozzle screwed onto the end of the hose, there isn't any pressure but put your thumb over the end to restrict the flow of water and it will definitely build pressure inside the hose.

As far as 'capping' a Model-A oil pump, when I have done this I used brass and brazed onto the end of the pump on the outside of the housing by the upper bushing. If you examine the pump, generally there are two flat areas that allow oil to bypass. I just put the pump housing in the lathe and machine the brass round to match the OD of the remaining portion of the pump. This just forces more oil out of the slots just under that upper bushing, and when there is a center main oil line, it creates a little pressure to force oil into the bottom of the bearing cap. FWIW, I never drill & thread the oil pump housing. Instead I just drill & thread the block itself. I think the pictures below show another way on how we do it.


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[Joe K]

Glyptal on the engine block interior is a nice touch.

I just bought my first can of Spray Glyptal - cough-choke.


Joe K

[Synchro909]

Originally Posted by Jim Brierley

Syncro, you restrict the outlet of the pump??? Sounds like that is defeating the purpose of it all except the center main.

With a 25 psi oil pressure relief valve, oil is trying to exit the top of the pump at 25 psi. With the original arrangement, it exits at 3, maybe 4 psi. By leaving some way for 25 psi oil to enter the valve chamber, I have enough oil to lubricate the front and rear mains the conventional way.
An alternative (and my first method) was to allow the oil from the middle bearing to flow back UP the original oil hole, back into the valve chamber after going through the middle bearing. When I plugged that hole, I slightly enlarged the exit hole for the oil into the valve chamber.
I must have done something right - I have about 70,000 hard miles on that engine now and it's still going.

Brent, I understand your reservations about drilling and tapping the oil pump housing but I did it without a problem.

[oldspert]

I have looked at the pics on the old Dennis Piranio website and Brents pics. The tube is actually connected at different locations in the block. How does each tap into the oil passage for pressure? Dennis's is tapped, (in what appears to the pan rail) and Brent's is inside the block. ??

[katy]

Brent, I noticed you used flare fittings, that's much better than compression fittings. Good job.

[BRENT in 10-uh-C]

Originally Posted by oldspert

I have looked at the pics on the old Dennis Piranio website and Brents pics. The tube is actually connected at different locations in the block. How does each tap into the oil passage for pressure? Dennis's is tapped, (in what appears to the pan rail) and Brent's is inside the block. ??

I install mine into the same Cylinder Block passage as the Oil Pump end and the Oil Pump Drive Bearing slip into. I use a ²¹⁄₆₄" drill bit in a 90° right angle drill to bore the hole. Then I use a tapered reamer followed by an ⅛" pipe tap for the block fitting.

Originally Posted by katy

Brent, I noticed you used flare fittings, that's much better than compression fittings. Good job.

I guess I should start by saying these aren't my design. I have been purchasing these from Ron's Machine over the years. They are flared however they are not double-flared as hopefully you can see in the picture. The tubing is copper however it appears to be the same material as used in industrial instrumentation work. Although copper can vibrate and fracture over time, I think because of the short length and gentle bends, it stays pretty rigid. Because of the orientation of the fittings on each end, and the rigidity of the tube, it may not be that big of a deal if ferrules were used.


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[Dan McEachern]

Garden variety compression fittings on copper tubing tend to crack at the point where the ferrule bites into the tubing so they are not the best fitting for inside an engine where they are unaccessable. Generally flare fittings are a much better choice. Inverted flares are not the best, but where there is not much room to make a connection, they are still better than compression fittings. If you must use compression fittings, instrumentation fittings such as Parker, Gyrolok or Swagelok are preferable but are not inexpensive.

[mcgarrett]

Dan,
You make an excellent point about not using compression fittings; I hadn't thought about the inherent hazard of the copper tube fatiguing and breaking where the ferule bites into the tubing. I'll look for the brass fittings that Brent uses.

[ModelA29]

Jim Brierley's book 4 Bangers and me has a photo on page 39 where the tube is feeding all 3 mains. I'd think an orifice in the line would be desired to make sure the other areas still get enough oil.

[Jim Brierley]

Originally Posted by ModelA29

Jim Brierley's book 4 Bangers and me has a photo on page 39 where the tube is feeding all 3 mains. I'd think an orifice in the line would be desired to make sure the other areas still get enough oil.

An orifice is a restriction, not recommended. Bendix air brake fittings support the line very well, available at truck parts stores. The system shown in my book are used with a full pressure system, so everything gets oil.

[Gene F]

Originally Posted by BRENT in 10-uh-C

I install mine into the same Cylinder Block passage as the Oil Pump end and the Oil Pump Drive Bearing slip into. I use a ²¹⁄₆₄" drill bit in a 90° right angle drill to bore the hole. Then I use a tapered reamer followed by an ⅛" pipe tap for the block fitting.





I guess I should start by saying these aren't my design. I have been purchasing these from Ron's Machine over the years. They are flared however they are not double-flared as hopefully you can see in the picture. The tubing is copper however it appears to be the same material as used in industrial instrumentation work. Although copper can vibrate and fracture over time, I think because of the short length and gentle bends, it stays pretty rigid. Because of the orientation of the fittings on each end, and the rigidity of the tube, it may not be that big of a deal if ferrules were used.


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Brent, how in the world do you get that fittings' shoulders to pass (rotate) without hitting and stopping you from threading it into (installing after threading) the block. Those surfaces, or boses, aren't they hitting the shoulder of the fitting? The throws on the crank look very close? Is this a kit you guys sell?

When you drill and tap the car, how do you do that? Do you lay the cap over a big dowell rod, or a wood fence post or something? What if you drill a smaller hole for that last little bit of the cap, so you can leave more babbit? Also, seems like a bigger bit might "snag" the babbit, whereas a 1/8" might be less likely and still provide oil. Lets face it, "a little dab will do ya". LOL

[Gene F]

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So how is this passage (pictured) not giving oil to the center main? Meaning why do we need another feed?

[40 Deluxe]

Originally Posted by Gene F

So how is this passage (pictured) not giving oil to the center main? Meaning why do we need another feed?

That passage is just a dribble feed-gravity flow from the valve chamber. Mains are starved for oil until oil warms up on a cold day. The center main is stressed the most, so needs the most oil. Adding this line direct from the pump gives the extra oil that the center main needs in a quick, cheap and easy modification.

[BRENT in 10-uh-C]

Originally Posted by Gene F

Brent, how in the world do you get that fittings' shoulders to pass (rotate) without hitting and stopping you from threading it into (installing after threading) the block. Those surfaces, or boses, aren't they hitting the shoulder of the fitting? The throws on the crank look very close? Is this a kit you guys sell?

When you drill and tap the car, how do you do that? Do you lay the cap over a big dowell rod, or a wood fence post or something? What if you drill a smaller hole for that last little bit of the cap, so you can leave more babbit? Also, seems like a bigger bit might "snag" the babbit, whereas a 1/8" might be less likely and still provide oil. Lets face it, "a little dab will do ya". LOL

I drill the block first, then I have a small tapered reamer to create a hole that a tapered pipe tap like, then I thread the block. There is room to rotate the fitting. The throws of the crankshaft are close, but not too close to cause concern,

Ron's Machine in Shandon, OH will likely have everything you need.

I just set the cap in a Mill Vise and plunge thru it with a drill. If you are worried about the Babbitt material breaking loose from the cap, then the cap was not properly tinned. I use a drill and then a tapered reamer before using a pipe tap. The hole thru the Babbitt is the same size as the pilot drill size. I have a small countersink that I use to flare the end of the bearing material. The thing I would not care for is if you are using the bearing material as a orfice, then the oil may find its way tunneling between the bearing material and the metal cap.

Originally Posted by Gene F

So how is this passage (pictured) not giving oil to the center main? Meaning why do we need another feed?

It is giving oil to the Center Main. The main difference is the oil entering the top of the journal is gravity fed to the crankshaft, whereas the oil entering thru the bottom is pressure fed.

[PC/SR]

Piraino's Parts has a very handy kit that taps into the oil passage. Kit includes the tap. The advantage of his kit is that the vibration for the line and block are the same. Cheap too. https://www.modelaparts.net/parts.htm/partsdept.htm

[nkaminar]

Just one comment. Joe K in post #14 made a comment that the pressure was not enough to force hydrodynamic separation (of the journal to the bearing). The hydrodynamic separation is caused by the rotation of the journal in the bearing. There is a wedge of oil formed that is dragged along with the journal and this actually does the separation. The pressure that is formed is many times more than the oil pressure, even in a modern engine.

[Synchro909]

Originally Posted by nkaminar

Just one comment. Joe K in post #14 made a comment that the pressure was not enough to force hydrodynamic separation (of the journal to the bearing). The hydrodynamic separation is caused by the rotation of the journal in the bearing. There is a wedge of oil formed that is dragged along with the journal and this actually does the separation. The pressure that is formed is many times more than the oil pressure, even in a modern engine.

Neil is quite correct. The sole purpose of oil in the engine is to keep the bearings cool. The fact that it is slippery helps. Guys who race these engines set their bearings with a wider clearance than most of us so that the oil can flow through quickly, carrying heat with it. By supplying oil under pressure to the bearing, more oil flows through it while the engine relies on hydrodynamic pressure to keep the crank journal from contacting the bearing. There is a relationship between the two but they are different.

[SAJ]

The hydrodynamic pressure in car engines needed to keep the bearing surfaces separated is far in excess of oil pump feed pressure. Anywhere from maybe 1000 to 6000 or more psi depending on engine speed, bearing load, clearances etc etc. Spark advance has a big effect on bearing load, the ideal maximum piston load from combustion being at about 17 deg ATDC for best power (usually quoted at 15 to 20 deg ATDC) for petrol engines. This maximum oil pressure occurs a bit after bottom dead centre in the bearing, since the journal runs a bit off centre from the bottom of the cap.
One can calculate the bearing load per square inch from engine torque and the angle at which it is maximised for a given engine. And hence the hydrodynamic oil pressure needed to keep the bearing surfaces seperated to avoid "boundary lubrication" such as occurs during engine start up before the high pressure hydrodynamic film has formed. But too involved to do here!
So an interesting question is how does oil from the pump at 45 psi manage to feed into an area where hydrodynamic pumping of the bearing is generating at least 600 psi and a lot more at higher revs?
I don't doubt that feed into the bottom high load area helps, since it has been proven many times practically. But i feel intuitively that feed pressure into the top of the bearing where gravity normally supplies it would work even better. Does any one feed oil pressure here?
SAJ in NZ

[BRENT in 10-uh-C]

Originally Posted by PC/SR

Piraino's Parts has a very handy kit that taps into the oil passage. Kit includes the tap. The advantage of his kit is that the vibration for the line and block are the same. Cheap too. https://www.modelaparts.net/parts.htm/partsdept.htm

With Dennis passing away and them having a sale last June, is Beth still running the store?

https://www.fordbarn.com/forum/showp...8&postcount=17

[Planojc]

Yes Beth is still in business but has moved from Denton to Celina Tx. Phone number is still the same.

[alexiskai]

Originally Posted by BRENT in 10-uh-C

With Dennis passing away and them having a sale last June, is Beth still running the store?

https://www.fordbarn.com/forum/showp...8&postcount=17

I just talked to Beth and she says the center main kit is discontinued.

[Synchro909]

Originally Posted by SAJ

The hydrodynamic pressure in car engines needed to keep the bearing surfaces separated is far in excess of oil pump feed pressure. Anywhere from maybe 1000 to 6000 or more psi depending on engine speed, bearing load, clearances etc etc. Spark advance has a big effect on bearing load, the ideal maximum piston load from combustion being at about 17 deg ATDC for best power (usually quoted at 15 to 20 deg ATDC) for petrol engines. This maximum oil pressure occurs a bit after bottom dead centre in the bearing, since the journal runs a bit off centre from the bottom of the cap.
One can calculate the bearing load per square inch from engine torque and the angle at which it is maximised for a given engine. And hence the hydrodynamic oil pressure needed to keep the bearing surfaces seperated to avoid "boundary lubrication" such as occurs during engine start up before the high pressure hydrodynamic film has formed. But too involved to do here!
So an interesting question is how does oil from the pump at 45 psi manage to feed into an area where hydrodynamic pumping of the bearing is generating at least 600 psi and a lot more at higher revs?
I don't doubt that feed into the bottom high load area helps, since it has been proven many times practically. But i feel intuitively that feed pressure into the top of the bearing where gravity normally supplies it would work even better. Does any one feed oil pressure here?
SAJ in NZ

SAJ, you are spot on with that post. I have seen pictures of modifications done to an A engine where plumbing is added tot he valve chamber to force oil down the original oil passages to the main bearings. That plumbing is not an easy task.

[oldspert]

Originally Posted by Planojc

Yes Beth is still in business but has moved from Denton to Celina Tx. Phone number is still the same.

I thought Dennis had moved from Celina to Denton. Years ago his shop was in Celina.

[Planojc]

True, but she just recently sold the shop in Denton and moved back to Celina. Still selling parts.

[1928 Sport Coupe]

[ModelA29;2289017]Jim Brierley's book 4 Bangers and me has a photo on page 39 where the tube is feeding all 3 mains. I'd think an orifice in the line would be desired to make sure the other areas still get enough oil.]

I have a few questions about this thread.
If you pressurize the center main bearing why not all three?
Is there any advantage or disadvantage to doing all three?
Would the oil tubes in the valve chamber going to the bearings need to be plugged? Or could the pressurized oil be run through the valve chamber tubes?
How would either affect the oiling to the camshaft.
I have not had a Model A engine apart in 30 or so years so I am a little rusty on the internal workings.
Sorry if I ask stupid or too many questions.
Thanks

[Synchro909]

Originally Posted by 1928 Sport Coupe

[ModelA29;2289017]Jim Brierley's book 4 Bangers and me has a photo on page 39 where the tube is feeding all 3 mains. I'd think an orifice in the line would be desired to make sure the other areas still get enough oil.]

I have a few questions about this thread.
If you pressurize the center main bearing why not all three?
Is there any advantage or disadvantage to doing all three?
Would the oil tubes in the valve chamber going to the bearings need to be plugged? Or could the pressurized oil be run through the valve chamber tubes?
How would either affect the oiling to the camshaft.
I have not had a Model A engine apart in 30 or so years so I am a little rusty on the internal workings.
Sorry if I ask stupid or too many questions.
Thanks

You'll get several different answers to that series of questions. Oh, and BTW, there cannot be too many questions.

If you pressurize the center main bearing why not all three?
In my case, I was lazy. I did the middle one because it is the one that is the first to fail. I figured pushing more oil through it would increase the flow of oil through it, helping keep it cool.

Is there any advantage or disadvantage to doing all three?
IMO, the front and rear main bearings are robust enough that while pressure feeding them might increase their life, the effort is not worth it.

Would the oil tubes in the valve chamber going to the bearings need to be plugged? Or could the pressurized oil be run through the valve chamber tubes?
I've seen it done both ways but as I said above, the plumbing in the valve chamber to force oil down all 3 of those holes is not easy to squeeze in there.

How would either affect the oiling to the camshaft.
Oiling though the original tubes would affect the cam shaft bearings unless provision was made to still have the floor of the valve chamber flooded with oil. If oil were pressure fed through the bearing caps and then exit UP the oil tubes, the cam bearings would be fine.

[BRENT in 10-uh-C]

Originally Posted by 1928 Sport Coupe

[ModelA29;2289017]Jim Brierley's book 4 Bangers and me has a photo on page 39 where the tube is feeding all 3 mains. I'd think an orifice in the line would be desired to make sure the other areas still get enough oil.]

I have a few questions about this thread.
If you pressurize the center main bearing why not all three?
Is there any advantage or disadvantage to doing all three?
Would the oil tubes in the valve chamber going to the bearings need to be plugged? Or could the pressurized oil be run through the valve chamber tubes?
How would either affect the oiling to the camshaft.
I have not had a Model A engine apart in 30 or so years so I am a little rusty on the internal workings.
Sorry if I ask stupid or too many questions.
Thanks

In a nutshell, there really isn't a need to pressurize all three. The size of the rear main bearing is WAY more adequate than needed, and it receives plenty of oil thru gravity. If you were to pressurize the rear main, then you must figure out how to effectively, -and reliably seal the rear of the rear main to keep it from leaking oil out into the flywheel housing. The tubes that feed the mains are the same tubes as used for the horn rod and the center hood rod. They are a rolled tube that will leak if pressure is added. The camshaft oiling is not compromised.

[alexiskai]

Originally Posted by BRENT in 10-uh-C

I guess I should start by saying these aren't my design. I have been purchasing these from Ron's Machine over the years.

If anyone's interested, I called Ron's and they said the kits are available for general purchase for $45 plus shipping.