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01-27-2024, 11:46 AM | #1 |
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Pressurized center main bearing?
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. |
01-27-2024, 12:17 PM | #2 |
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Re: Pressurized center main bearing?
See this link. http://www.modelaparts.net/special.h...entermain.html
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01-27-2024, 12:35 PM | #3 |
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Re: Pressurized center main bearing?
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.
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01-27-2024, 01:34 PM | #4 |
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Re: Pressurized center main bearing?
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? |
01-27-2024, 03:51 PM | #5 |
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Re: Pressurized center main bearing?
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?
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01-27-2024, 07:16 PM | #6 |
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Re: Pressurized center main bearing?
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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.
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01-27-2024, 08:07 PM | #7 |
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Re: Pressurized center main bearing?
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. |
01-28-2024, 12:03 AM | #8 | |
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Re: Pressurized center main bearing?
Quote:
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01-28-2024, 10:52 AM | #9 |
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Re: Pressurized center main bearing?
It sounds like the oil passage in a B model
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01-28-2024, 06:32 PM | #10 |
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Re: Pressurized center main bearing?
Maybe but who would want to go to all that work when the main bearings in a B engine are already pressure fed?
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01-28-2024, 07:34 PM | #11 |
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Re: Pressurized center main bearing?
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.
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01-28-2024, 07:39 PM | #12 | |
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Re: Pressurized center main bearing?
Quote:
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
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01-30-2024, 01:07 PM | #13 |
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Re: Pressurized center main bearing?
Syncro, you restrict the outlet of the pump??? Sounds like that is defeating the purpose of it all except the center main.
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01-30-2024, 01:38 PM | #14 | |
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Re: Pressurized center main bearing?
Quote:
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
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01-30-2024, 02:05 PM | #15 | |
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Re: Pressurized center main bearing?
Quote:
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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01-30-2024, 02:32 PM | #16 |
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Re: Pressurized center main bearing?
Glyptal on the engine block interior is a nice touch.
I just bought my first can of Spray Glyptal - cough-choke. Joe K
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01-30-2024, 05:44 PM | #17 | |
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Re: Pressurized center main bearing?
Quote:
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.
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I'm part of the only ever generation with an analogue childhood and a digital adulthood. Last edited by Synchro909; 02-02-2024 at 11:51 PM. |
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01-30-2024, 07:17 PM | #18 |
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Re: Pressurized center main bearing?
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. ??
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01-30-2024, 08:51 PM | #19 |
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Re: Pressurized center main bearing?
Brent, I noticed you used flare fittings, that's much better than compression fittings. Good job.
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01-31-2024, 02:28 PM | #20 | ||
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Re: Pressurized center main bearing?
Quote:
Quote:
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