Phillip Robinson

Crankshaft bearings

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Is it wise to use second hand bearings for the crankshaft. I have 3 sets of old , used bearings, for a 4 cylinder ford flat motor. What is accepted as being the best idea, new or used, for 75 year old motor.

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What about the condition of the crank shaft ? Is the bearing  in good condition ? I see no reason why not. What might influence performance is pistons and rings fit in the block. If done properly you should get a few miles out of it.   NEW NEARLY AS ALWAYS IS GOOD. but I am subject to correction here. 

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23 hours ago, Phillip Robinson said:

Is it wise to use second hand bearings for the crankshaft. I have 3 sets of old , used bearings, for a 4 cylinder ford flat motor. What is accepted as being the best idea, new or used, for 75 year old motor.

 

Depends on the clearances and existing wear patterns of shaft and bearings.

If you're just putting together pieces that have been disassembled from the same location, not a problem, if you have part wornn bearings and crank pins that need just a light polish/linish, not a problem; beyond these parameters not such a good idea. 

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Thanks for replies. I suppose the question is just a general question for any engine. In this case, crankshaft reground and from a different motor. Having a look at different web sites to see about bearings being damaged, and thus not usable. Adds about $500 more to motor repair.

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2 hours ago, Phillip Robinson said:

Thanks for replies. I suppose the question is just a general question for any engine. In this case, crankshaft reground and from a different motor. Having a look at different web sites to see about bearings being damaged, and thus not usable. Adds about $500 more to motor repair.

 

Okay,  having had the crankshaft reground would mean the bearings actually need  to match the newly machined crankshaft pin dimensions. ie you're probably needing specific under size bearing shells. Using second hand bearings in this instance would undo the money you've just invested in the crankshaft. 

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There is also a question as to quality of babbit. I understand the old original babbit is not near as good as the stuff we have now. I guess it depends on what you trying to accomplish. The old bearing can be fit to the ground crank, all it takes is time and experience.

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46 minutes ago, AHa said:

The old bearing can be fit to the ground crank, all it takes is time and experience.

 

You have aroused my curiosity. How do you go about doing that.

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The bearings are not " babbitt" , as the conrods are the newer style, with later bearings. If using a new bearing, it seems like I might have to get it checked it for size, 

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All bearings have Babbitt surfaces. Insert bearings just have a very thin layer of Babbitt.

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I guess I assumed the question was concerning babbit main bearings. If there is enough bearing, they can be coated with prussian blue, torked down, and hand scraped to fit.

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  • Do yourself a favor. Install new bearings that are properly sized for your newly ground crankshaft. Whoever did the crankshaft can advise you on the size bearings you need, and how to install and torque them correctly. That's far cheaper than having to do this job all over again. $500 is nothing compared to the money, time and future angst that mismatched or worn bearings will cause you later.  
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On 9/21/2019 at 4:22 PM, AHa said:

I guess I assumed the question was concerning babbit main bearings. If there is enough bearing, they can be coated with prussian blue, torked down, and hand scraped to fit.

If the crank is undersize you would probably have to file the caps to get proper clearance and of course then the bearing is egg shaped and will also impact anyone who wishes to redo the bearings at a later date.

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4 hours ago, jrbartlett said:
  • Do yourself a favor. Install new bearings that are properly sized for your newly ground crankshaft. Whoever did the crankshaft can advise you on the size bearings you need, and how to install and torque them correctly. That's far cheaper than having to do this job all over again. $500 is nothing compared to the money, time and future angst that mismatched or worn bearings will cause you later.  

 

I agree.  I wouldn't install used bearings on a freshly ground crankshaft.  I worked in a shop that had a crankshaft grinder. As soon as the crankshaft was ground a counterweight was stamped with the undersize the bearings needed to be.   If it was stamped 010/020 it meant .010 undersize main bearings were needed and  .020 undersize rod bearings.  I can't imagine the bearing inserts costing $500 in less they are special order or almost impossible to find.

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The discussion here assumes that there are new bearings are available for the application. In the case of the Ford new bearings are available, but in a broader sense there are some cars that become derelict because inserts don't exist. Case in point of real world concert for those of us who own 1936-42 Studebaker Presidents. Insert bearings for this engine have not been available for years, and that's how long some people have been looking for them. In this case trying to piece together a bottom end from parts from another engine beats the alternatives. 

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Right. In a perfect world we all have the finances and wherewithall to do whatever it takes to keep our cars running but in this present world we do what we can. Is this car going to be driven every day to work, 60 miles round trip, or occasionally driven, in which case a scraped in bearing will suffice. $500 is a lot of money to me, and that's just the quote on main bearings. How much more are we talking before somebody can drive the car? Once he wins the lottery, the motor can be rebuilt properly.

 

We are told the value of our cars are coming down. Can all of us afford to put money in our projects we will never see again? I think not, but we all want to enjoy our cars.

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On 9/20/2019 at 3:33 AM, Phillip Robinson said:

Is it wise to use second hand bearings for the crankshaft. I have 3 sets of old , used bearings,

 

On 9/21/2019 at 5:46 AM, Phillip Robinson said:

I suppose the question is just a general question for any engine. In this case, crankshaft reground and from a different motor.

 

I can't see any competent mechanic installing a crankshaft that has been ground into an engine using used standard size bearing inserts.   The engine would knock like hell if you did and oil pressure would be almost non-existent. I guess you could find a mechanic that would be willing to do a half-ass job by grinding, shimming or modifying the inserts in some manner but don't expect him to stand behind his work.  That is the kind of thing that's done when your objective is to get the engine to run long enough to push the car off on someone else.  As a mechanic and machinist for over 30 years my conscience wouldn't allow me do that.

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21 hours ago, Buffalowed Bill said:

The discussion here assumes that there are new bearings are available for the application. In the case of the Ford new bearings are available, but in a broader sense there are some cars that become derelict because inserts don't exist. Case in point of real world concert for those of us who own 1936-42 Studebaker Presidents. Insert bearings for this engine have not been available for years, and that's how long some people have been looking for them. In this case trying to piece together a bottom end from parts from another engine beats the alternatives. 

 

The fact remains that if you fit bearings that don't conform precisely to the crankshaft dimensions then you have every chance of damaging the crankshaft, and then you're back to where you started. 

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Agreed, but if where you started was as a derelict car, what difference does it make. I would never put together an engine without checking the clearances, and granted finding the right combination would entail a good deal of luck but.... Then again you could find someone willing to rebabbit your thin shell inserts, and grind the crank, transport the engine to his shop, then transport it again to another shop, where it can be properly align bored. By the time you have paid over $2000 for forged aluminum pistons, because they too are unavailable, and had the machine work done, you might be ready for bankruptcy, but the next guy who gets the car might be happy as hell.  Why don't you ask me why I know about the process.

 

Putting an engine together from used parts may not be my choice, but I can't prejudge what someone's financial situation is. Sometimes the willingness to take a chance, beats the alternative of doing nothing.

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Your not just talking about money out of pocket.  There's also the value of what you have to be considered.

 

Yes, you can save money by taking short cuts, but how much will it be worth if the bottom end of the motor gets trashed ?   The main and rod bearings have to withstand tremendous forces and be the correct fit to maintain the correct oil film thickness to support those loads, reduce friction, and carry away heat. When they aren't, the damage - clock starts ticking.  

 

Paul

Edited by PFitz (see edit history)
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Paul, 

 

You're preaching to the choir, necessity would have to matched by parts availability. Choice would not be the one I would make, but for some it may be the only choice. In the case of the Ford these are pretty simple engines and readily available, the guy has the parts, or thinks that he has the parts available that will match the application. I don't know if what he has will work. It's up to him to determine. He asks about the best. I think most agree that new quality parts would be the best solution. Someone more familiar with the quality of available new bearings, for this car, would have to comment.

 

My comments were aimed at the situation with the Studebaker President, where absolutely no new parts are available. A decade ago a Studebaker owner researched available bearings for other applications, which could be machined to work. Problem solved, until those substitute bearings went extinct. It's been years now, and there are numerous owners sitting on projects the problems for which they feel they have no solution. I hope that I don't have to notate what can, and will happen to a project that sits derelict, for an extended period of time. So what would you do?

 

Bill

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Bill,

The options are not just cut corners or let it sit forever. One option not discussed is that if there isn't enough money to do the job so that there is no risk of damaging the value of what he has, is consider selling the car to someone who has the resources to do the bearings the way they should and find a car that is not such an expensive  project. A tough choice to make, but sometimes the wiser choice is tough.  

 

Like they say about playing poker - know when to hold 'em and know when to fold 'em.  

 

Paul

Edited by PFitz (see edit history)

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My babbitt guy would not just re-babbitt my bronze backed replacable mainbearings in my Pontiac.  He however re-cast the bronze backing and the babbitted the new shells.  He said simply removing the bronze shells from an old engine could/would/might distort them and the only correct repair was new shells.  $1500 for three bearings and shells which I thought was very reasonable.

I have used old parts from other engines and reused parts from the same engine and have never found it to be satisfactory.  If it was a trailer queen or a car that was just used around town it might work for a while but certainly not reliable.  Drove home almost a hundred miles in an old Chev with a piece of belt to replace a burnt out rod brg and almost the same distance on five cylinders with a rod and piston removed.  No money for a tow and needed to get home.

There is really only one way to repair an engine.  That is the problem with a new to you vehicle, you have no idea what or how any repair has been made in the past.

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Paul,

 

You might think that it's OK to turn an otherwise restorable vehicle into a parts car, because the engine parts are unavailable. For me it's not OK. If you think that I am exaggerating, not true, I see it every day in my world. It's happening as I speak. So I ask again, what is your solution when the alternative to a necessary $7-10 K rebuild is doing nothing? There is no market for one of these cars needing this level of work! Doing nothing virtually guarantees the car's destruction. This is not a worst case scenario, it is simply reality.

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There is technically nothing wrong with using used bearings, if they are solid and in good condition, BUT.... Are they going to fit?

 

They DO need to fit properly, and the odds are against it. Proper bearing clearance will be specified by the maker of the engine, but is typically around 0.015-.002. There really isn't any wiggle room. If a crank is ground, it will generally be to a standard undersize, like -.010 or -.020 . New bearings will be made to work with those measurements. If the used ones have any wear AT ALL they aren't going to fit, even if they are the correct undersize.When you measure them, they will be out of spec. Yes, if they were in spec it would be fine, but I think you might have better luck with the lottery.

 

If the bearings are too tight they will spin and tear up the block or rod. If they are even a tiny bit too loose, too much oil will leak out, and the engine will have trouble keeping oil pressure. That could lead quickly to a failure, and even if it didn't, they would probably make noise and have a short life.

 

Sometimes there have been tiny undersizes available in bearings, even used by the factory in some engines, that are -.0005, -001, etc. This can be used to deal with manufacturing tolerances, and or a little crank wear. These are generally only for standard size cranks (that have not been ground). I have never heard of anything like -.0105 or -.011 .

 

Inspect the bearings for any damage, and check your clearances with plastigage. That will tell the story.

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