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Neil's '41 Super Model 51


neil morse

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No need to apologize, John.  I was actually just logging on to say I was going to send you a PM -- my intention being to take another stab at trying to help you get this straight.  You saved me the effort! 😄

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1 hour ago, JohnD1956 said:

And now that i have thought about it more and looked at some rebuilding kits I realize that I was incorrect in my application of theory. Sanding the oil pump cover flat is right and the plate would be for the inside of the pump body where it would be much more difficult to get a flat surface. So with all these wasted digits I would say my earliest post on this topic is definitely incorrect.  My apologies. Moving on...

 

 Hey, we have all been there. Few can know them all. Before starting work on George, eleven or so years ago, I thought I KNEW Buicks.  Not at ALL.  I have learned a lot. Enough to realize I am a novice yet.

 

 Ben

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Automotive Archaeology

 

From the picture I posted earlier, you can see that the pistons on my car look quite new.  Today, I confirmed that the con rods and rod bearing caps are stamped with numbers indicating the cylinders (1 through 8).  According to Don Micheletti, this indicates that the engine was rebuilt by a professional shop at some point.  Good news!

 

rod.thumb.jpg.4cb2c2e4f16b7fa82067cb8474c87c81.jpg

 

 

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13 minutes ago, John_Mereness said:

Pack the gears only (I have actually seen people pack the entire pump and that is BAD) or pull the coil wire and turn it over until you have built oil pressure. 

 

So ... I have read some conflicting things about the procedure when putting the pump back in.  Several people have mentioned the importance of packing the gears with Vaseline.  I have also been told to pack the gears with grease.  On another thread (from a reputable source), the recommendation before reinstalling the pump is "Pour oil into the new-rebuilt oil pump to fill it and "prime" it.  You can feel the resistance of the gears when it fills with oil."  In any case, the idea of pulling the coil wire and turning over the engine to build up pressure seems like a good precaution.  Comments?

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I personally have just put a healthy coat of grease on pump gears (not packed them) and then turned engine over with spark plugs out until I build a few pounds of oil pressure on gauge - I learned from a few mechanics that I think are good, but everyone seems to have a differing opinion.  

Edited by John_Mereness (see edit history)
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At least coat the gears with grease.

In a perfect world, I'd pull the distributor and drive the pump with an electric drill until I had oil pressure on the gage = easy to feel via the drill.

I wouldnt recommend that for Neil. Pulling the coil wire and cranking until he sees pressure would be best - If his battery can stand it.

 

I had an instance when I didnt coat the gears and the pum would not prime. That surprised me. I hjad to drop the pan and grease the gears. Ehgine was on a test stand.

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Thanks, John and Don.  I will make sure my battery is fully charged -- I have it on a trickle charger while I'm doing this work, so it shouldn't be a problem.  I'm looking forward to getting everything buttoned back up, but I've still got a ways to go.

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When you crank up oil pressure using the starter, remove the spark plugs. Your battery and your starter will thank you.

 

Vaseline, grease, assembly lube, or oil are all fine to pack the pump with to help it prime. Oil is not preferable unless you are going to do the cranking right away, as it will slowly drain out of the pump. Be sure to put something in though, it saves a lot of cranking.

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Neil,

What drove to to pull the pan?  Idle  hands are the devils work shop?

 

As to the oil pump with gear style pumps the OEM should have a clearance spec as to how much clearance there is between the contact faces. This will indicate if the bearing (journals) on which the gears ride are worn. Also look at the gear lobes themselves to see it there is any deformation of the lobe (gouges). Look at the root of the lobes to see it any FOD is in the "valley". Your end plate looks fine. But if you want to lap it that would be fine. But be aware that there is no gasket between the housing and end plate. So you need to keep the surface flat. 

Do you know how to lap surfaces? I (under the term shade tree mechanic) like to use a glass plate with 3M sandpaper taped down by the edges. I then use a figure 8 motion followed by a 1/4 every minute or so. 

 

Lapping the end plate will have NO effect on clearance. Lapping the housing will effect the end clearances between gear elements and the end plate.

 

With the clean pistons indicating that the engine has been reworked. I wonder what the material is that you found on the sump screen. Usually it is coke or bugs that got into the engine from the vent system.

 

I hate to see Vaseline used as it is a contaminate in an oil system. Do prime the oil pump prior to installation. This is done to give the pumping elements a film of oil to make the oil seal on the pump elements and housing. There is no need to pack the pump. Engine oils has a low enough viscosity that it will flow out of the pump and into the sump. This happens every time you shut down the engine. 

 

Please don't stress the starting system by dry running (fuel or ignition turned off) the engine thinking you are pre-lubing the engine prior to ignition. Just start the engine as you normally would keep the rpm low until you have good oil pressure. This should be just like what you do every time you start your engine, wether you pulled the oil pump or are going out for groceries! 

 

In rotating machinery where we need oil pressure prior to rotation we use accumulators to dump pressurized oil into the system. These simple car engines are not such machines. The oil film strength will protect the parts from metal to metal contact at the low power levels found at idle and cranking speeds.

 

All the best,

Konrad

Edited by Konrad
Typos (see edit history)
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Thanks for all your input, Konrad!  Yes, I took on this job because I figured I had nothing else to do since we can't go fly our model planes and I wanted to clean everything up and try to learn a bit more about my engine (which I have).  I'm going to have to call you up to sort through all the questions you are asking and suggestions you are offering.  But, yes I remembered your suggested procedure for lapping, and that's exactly what I did.

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11 minutes ago, Konrad said:

If the pump is still apart, can we see the lapped end plate? I'm sure it is flat within 3 helium light bands.B)

 

3 helium light bands is real flat, like carbon face seal flat! So I'm just joking.

 

Yes, but is it "true level?"

 

 

Edited by Matt Harwood (see edit history)
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1 hour ago, Konrad said:

If the pump is still apart, can we see the lapped end plate? I'm sure it is flat within 3 helium light bands.B)

 

Here you go:

 

oil_pump7.thumb.jpg.a917a176f1c18762d834530dd80d7d78.jpg

 

Here's the "before" pic again for comparison:

 

oil_pump2.thumb.jpg.8200808fd1bba9cdae09162fca2c9237.jpg

 

I checked the clearance with Plastigauge, and it came out to .002".  I read in another thread that the factory spec is .0005 to .004, so I'm satisfied (and also sick of endlessly doing figure-8 patterns on a piece of sandpaper taped to a piece of glass!).  (I would have checked it on the helium light band scale, but I loaned my helium light band gauge to Konrad and he hasn't returned it.) 😜

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This is to see if I can post a photo more than anything else.

 

Lapping looks good. I see very little roll over at the periphery. Cover looked great even before your hours on the lapping table. As you can see the pumping elements hadn't rubbed past the surface finish marks left by the OEM grinder at time of manufacture.  The slight asymmetrical pattern is from the side loading of the pumping element from the pressure side. This allowed the pumping element to cock as there needs to be some bearing clearance between the pumping elements and the support journal. 

 

The short is that your oil pump looked and looks rather good.

oil_pump2.jpg.00d35af3801eb7408930dc7895f78739.jpg

Edited by Konrad (see edit history)
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I had some questions ask of me about the various marks.  At the factory they used a horizontal type surfacing wheel. For ease of manufacturing the wheel is not perfectly flat to the direction of motion.This is why we don't see a cross hatch pattern in the OEM machining marks.  Because of axil loads, mainly from oil pressure needed to feed the gear journal,  we see circular wear marks in the end plate made by the pumping elements. 

 

 

41 oil pump plate.jpg

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More questions asked. I hope I can clear things up a bit. Now I need to say I haven't seen the pump nor do I have any engineering drawings of the pump. So this in all likelihood will be worth what you all paid.

 

Lapping and clearance changes.

Per the attached drawing the end clearance is controlled by Dimension "C" (Housing Cavity) minus Dimension "D" ( Element Length). Lapping Surface B will shrink the cavity depth Dimension "C". This will result in less clearance

Lapping Surface A will not change the clearances. It will make the oil feed trough shallower. 

 

I'm sure this makes things as clear as ink!:unsure:

 

 

41 pump housing.jpg

Edited by Konrad (see edit history)
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What I see going on. Again I haven't held the parts in my own hands.

 

As a result of the needed clearances in the bearing journals the pumping elements are allowed to move (axially and cant some what).

This canting is showing up as asymmetrical wear on the plate under one of the pumping elements. This canting it wearing the outside of the pumping elements ( see shadow in attached photo)

It is interesting to note that because of the oil feed trough the other element is lifted by the surface area and oil pressure away from the end plate. Notice the lack of machining marks on one element and the pristine look of the other. We can see every groove from the single point cutter!

Neil's pump.jpg

Canted gear.jpg

Edited by Konrad (see edit history)
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Konrad, thanks so much for doing those drawings and posting them here!  I understand the pump so much better now.

 

Also, just to clarify things for people who may have been trying to keep score, I previously posted that I got a Plastigauge reading of .002 on the clearance.  That was true at the time.  After reading Konrad's first post, I looked at the case and decided I might as well do some gentle lapping on the case side since it looked a little rough.  So the second Plastigauge reading of .0015 shown in the photo Konrad posted was after I lapped the case.  I was happy with that and quit while I was ahead.  As Don wisely said in an email to me, "be careful, if you make things so pretty that the pump binds, you'll be buying a new pump."

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13 hours ago, Konrad said:

Wise words!

I've been known to improve things to the point where they won't run (work)!

 

But before buying a new pump I'd lap the gears to regain the needed clearance.

 

 

18 posts and the last six were truly remarkable.  Stay aboard, contribute often Konrad.

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I've prepped the oil pan for paint and sprayed some primer on it yesterday.  Everything else is ready to go, but I'm still waiting for my Dante Red -- and now the USPS tracking site just says the package is "in transit" with no updates for five days.  Never a good sign.  Grrrrrr.

 

oil_pan3.thumb.jpg.45f268495acb5f9970863e00eedf7261.jpg

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On 4/29/2020 at 7:50 PM, neil morse said:

  As Don wisely said in an email to me, "be careful, if you make things so pretty that the pump binds, you'll be buying a new pump."

 

Story of my life. I get it to 99% and that little voice in my head (he's an absolute ass) says, "We can make it perfect! Let's do it!"

 

And then I fix it until it's broken.

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3 hours ago, Matt Harwood said:

 

Story of my life. I get it to 99% and that little voice in my head (he's an absolute ass) says, "We can make it perfect! Let's do it!"

 

And then I fix it until it's broken.

I was told there are many levels of restoration, but I can still win 100 points with parts that have flaws in them and there is a difference between in your hand under good light and fully assembled sitting on a show field.  These same people preached - "where are you going as you will be lucky to get 10K miles on this car over your lifetieme" (well, they were wrong there, but 40K plus miles on a restored car is pretty hard on it, so for the tour cars we just go for nice and fry other fish with the long term concours projects). 

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I think it's called tolerance. As a machinist, there is no such thing as perfect. There is nominal size. And what I normally aim for, most material condition (MMC) as opposed to least material condition (LMC). 

 

Modern spec's are written using geometric dimensioning & tolerancing (GD&T). This uses the shape of the feature in defining the tolerance zone. This controls a lot of the outliers we got using the classic Cartesian (X,Y) system.

https://en.wikipedia.org/wiki/Geometric_dimensioning_and_tolerancing

 

Hand fitting was often used in the old days to address these fit issues.

 

All the best,

Konrad

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I just learned that there is a 1/16 inch hole in the pressure relief valve. I assume this is to take some some load off and purge the pump at low speeds, like cranking speed. Now I’m sure it contributes to the low pressure reading some are noticing at idle. I read through some of the posts on this site and there often is a concern about low oil pressure. Most of these concerns are about idle oil pressure. As these bearing are plain bearings aren’t we dealing with  hydrodynamic  principles rather than hydrostatic lubrication system.

 
As I see light loads at idle, I don’t see any issue with “low” oil pressure at Idle. 
 
I believe the valve off to the side of the pump is a pressure relief assembly (valve), not a pressure regulator. If the Buick engineers sized the pump properly, and I’m sure they did, low oil pressure is a concern at engine speeds where the piston are putting load on the plain bearings. Not at idle where most of this pressure is lost to the bearing clearances.
 
 Now I’m taking about oil pressure not oil flow. As we don’t have turbo flow meter in our cars we are using oil pressure as an indirect way to measure flow.  
 
My concern is what is a safe oil pressure (HIGH)?  Here in sunny California we don’t see the cold temperature that would result is high oil viscosities that would normally move the oil pressure relief valve. I’m concerned that these valves might stick as a result of varnish as they rarely move.
 
Do any of the manuals mention this, upper and lowers oil pressure limits?
 
I ask this as it appears that there is a lot of angst about low oil pressure at idle, that I fear is leading to unnecessary disassembly of otherwise perfectly operating equipment.
 
All the best,
Konrad
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I've always just followed the racer's rule of thumb of 10 PSI per 1000 RPM. My 1929 Cadillac's idle spec is 12 PSI, and it sits right there on the button, hot or cold. My '41 Buick is about 20 PSI at hot idle, which I also think is plenty as long as it climbs back to 40-50 at speed, which it does. Konrad is exactly right that it doesn't take much oil pressure to be safe at idle, you just need a small barrier layer between the spinning parts, which are barely moving anyway. Modern oils are so good that idle oil pressure (as long as it's above 0) is kind of a non-issue.

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1 hour ago, Ben Bruce aka First Born said:

You did good, Neil.

 

Hey, let's not get ahead of ourselves, I'm not done yet.

 

However, my Dante Red paint showed up yesterday and I sprayed the pan this afternoon.  I should be putting everything back together tomorrow afternoon.

 

oil_pan4.thumb.jpg.9b574dcbc07593e683682226738520d6.jpg

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