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What is babbit and what is the purpose ? Does it take a specialty shop to rebabbit an engine or can any machine shop do it ? What would happen if you rebuilt an engine without new babbit and is it expensive ? Thanks wayne
What is the purpose and function of babbit ?
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Mike V. Florida
Well-known member
What is babbit and what is the purpose ?
Prior to 1940 just about every machine built used Babbitt bearings, and every mechanic was familiar with them. Babbitt metal is soft and easily damaged, which suggests that it might be unsuitable for a bearing surface. However, its structure is made up of small hard crystals dispersed in a softer metal, which makes it a metal matrix composite. As the bearing wears, the softer metal erodes somewhat, which creates paths for lubricant between the hard high spots that provide the actual bearing surface.
http://www.lindsaybks.com/dgjp/djgbk/babbitt/index.html
Does it take a specialty shop to rebabbit an engine or can any machine shop do it ?
It takes special jigs and tolls to do the job correctly. While simple in discription it takes skill and learning to do it correctly. Oh it is also part art.
What would happen if you rebuilt an engine without new babbit and is it expensive ?
Many shops install modern insert bearings (which by the way are shells with babbit applied). As for expensive, it's relative, This first time for inseart bearing to be done needs the block to be machined, the times after that just the shell need to be replaced along with any crank machining that would need to be done no matter which method is used.
Prior to 1940 just about every machine built used Babbitt bearings, and every mechanic was familiar with them. Babbitt metal is soft and easily damaged, which suggests that it might be unsuitable for a bearing surface. However, its structure is made up of small hard crystals dispersed in a softer metal, which makes it a metal matrix composite. As the bearing wears, the softer metal erodes somewhat, which creates paths for lubricant between the hard high spots that provide the actual bearing surface.
http://www.lindsaybks.com/dgjp/djgbk/babbitt/index.html
Does it take a specialty shop to rebabbit an engine or can any machine shop do it ?
It takes special jigs and tolls to do the job correctly. While simple in discription it takes skill and learning to do it correctly. Oh it is also part art.
What would happen if you rebuilt an engine without new babbit and is it expensive ?
Many shops install modern insert bearings (which by the way are shells with babbit applied). As for expensive, it's relative, This first time for inseart bearing to be done needs the block to be machined, the times after that just the shell need to be replaced along with any crank machining that would need to be done no matter which method is used.
Kevin in NJ
Well-known member
Babbitt is a bearing metal.
The original Babbitt formula is a mixture of mostly tin, some copper and anitmony for hardness and to limit shrinkage. Antimony expands as it cools.
Later a lead bearing material took on the name babbitt too. Lead based babbitt is only to be used with none impact loads.
Babbitt is nice in that the hard metals are small and the tin has the property of being a lubricant if the oil fails. This limits damage to the crank. The thick babbitt is also able to take hard particles and allow them to imbed to prevent them from harming the crank surface.
Anyone can pour and bore babbitt.
A lot of guys do it.
Few know how to work it properly.
There are certain rules the must be followed to ensure the metal crystal growth is fine and well distributed.
Some well known shops I know do not follow these rules. This means some bearings they pour are destined to fail from the moment it cools. Micro cracks will have already started.
Then there is properly peening the bearing into the block. Once poured the babbitt will pull slightly from the block. It is not bonded to the block, it is held mechanically. Even a slight mis-peen or peening when too cold will cause a failure. From the NOS parts we have acquired we know Ford did quite a bit of peening.
Then there is the proper setting up of the line boring to get the bearings inline and to size. The centerline must be parallel and the correct distance to the cam line. There are several line boring tools that were made with jigs to accurately set the crank centerline. Anyone can use the tools, but with any machining it is both and art and a science. You have to have the correct feel as well as knowing the math to set the bar accurately and repeatably. Then the bore needs to be checked for straightness. Checking is simple with ground bar, but some guys do not do this check. The big shops have a big tool that is hard to mess up, but they a lot and you have to have volume to afford it. The small guys have the line bores that require careful attention to set up repeatably and accurately.
What can you expect with babbitt?
You can expect up to 50,000 miles with a good babbitt job. You will have to take up the bearings a couple of times to account for wear. Babbitt lets you know when it is going to fail if you are listening. If the babbitt fails you will likely be able to limp home and only need to put in new babbitt.
Inserts will give similar life, but are just a prone to poor machine work causing failures. Except a failed insert job may cost you your block. I am also question how people talk a lot about how easy it is to put in new bearings like they do that a lot. If the insert fails it will do so with little warning. You will need a tow and you will need a crank and maybe a new block.
If you are going to have a block done and you plan on driving a lot then go to someone with a solid reputation. You must spend the money to get everything balanced and the crank reground one centers and so on. I personally prefer properly done babbitt over inserts. I would consider full new insert rods as they were made to use an insert. I would not consider a converted original rod.
The life of either bearing type is dependent on the quality of the job done by the person doing the work. I would have discussions (talk on the phone) with the shop mentioned above plus J&M Machine and Kohneke (I am not spelling this right he is active on this board) about what they can do for you.
So that is some stuff on babbitt in a nutshell. You can find some info on crank grinding at my website if you care to look.
The original Babbitt formula is a mixture of mostly tin, some copper and anitmony for hardness and to limit shrinkage. Antimony expands as it cools.
Later a lead bearing material took on the name babbitt too. Lead based babbitt is only to be used with none impact loads.
Babbitt is nice in that the hard metals are small and the tin has the property of being a lubricant if the oil fails. This limits damage to the crank. The thick babbitt is also able to take hard particles and allow them to imbed to prevent them from harming the crank surface.
Anyone can pour and bore babbitt.
A lot of guys do it.
Few know how to work it properly.
There are certain rules the must be followed to ensure the metal crystal growth is fine and well distributed.
Some well known shops I know do not follow these rules. This means some bearings they pour are destined to fail from the moment it cools. Micro cracks will have already started.
Then there is properly peening the bearing into the block. Once poured the babbitt will pull slightly from the block. It is not bonded to the block, it is held mechanically. Even a slight mis-peen or peening when too cold will cause a failure. From the NOS parts we have acquired we know Ford did quite a bit of peening.
Then there is the proper setting up of the line boring to get the bearings inline and to size. The centerline must be parallel and the correct distance to the cam line. There are several line boring tools that were made with jigs to accurately set the crank centerline. Anyone can use the tools, but with any machining it is both and art and a science. You have to have the correct feel as well as knowing the math to set the bar accurately and repeatably. Then the bore needs to be checked for straightness. Checking is simple with ground bar, but some guys do not do this check. The big shops have a big tool that is hard to mess up, but they a lot and you have to have volume to afford it. The small guys have the line bores that require careful attention to set up repeatably and accurately.
What can you expect with babbitt?
You can expect up to 50,000 miles with a good babbitt job. You will have to take up the bearings a couple of times to account for wear. Babbitt lets you know when it is going to fail if you are listening. If the babbitt fails you will likely be able to limp home and only need to put in new babbitt.
Inserts will give similar life, but are just a prone to poor machine work causing failures. Except a failed insert job may cost you your block. I am also question how people talk a lot about how easy it is to put in new bearings like they do that a lot. If the insert fails it will do so with little warning. You will need a tow and you will need a crank and maybe a new block.
If you are going to have a block done and you plan on driving a lot then go to someone with a solid reputation. You must spend the money to get everything balanced and the crank reground one centers and so on. I personally prefer properly done babbitt over inserts. I would consider full new insert rods as they were made to use an insert. I would not consider a converted original rod.
The life of either bearing type is dependent on the quality of the job done by the person doing the work. I would have discussions (talk on the phone) with the shop mentioned above plus J&M Machine and Kohneke (I am not spelling this right he is active on this board) about what they can do for you.
So that is some stuff on babbitt in a nutshell. You can find some info on crank grinding at my website if you care to look.