Lubricating the backs of bearings

[fabr]

Not a single place in your posted info even mentioned dry or otherwise. What was the point in the post?

Look guys,I'm not saying that dry is bad. On the contrary I feel that dry is much easier to keep "clean"during assembly but on the other hand I think I'm smart enough to see that a slight oil film will not cause any issue. Consider the clamp load of 8-10 MPa ,how much oil film will there be? Damn near zero as it will extrude out from under the shell as the cap is torqued in place. The only oil remaining is in the valleys of the hone pattern. Full contact is only achieved by the peaks of the hone pattern contacting the shell. Ever looked at the back side of a bearing under an inspection scope at say 50X or even a 100X ? Looks like the moon compared to the bore.

The point is I have looked and looked for any actual literature that says a film of oil or even a drenching of oil will cause a spun bearing. This IS what you guys are inferring. I have not even found any literature confirming that dry is better. If you guys have it I will stand corrected.

Some poor sap that is green as green can be working on an engine maybe for the first time and oiled the backs for whatever reason doesn't need to read that oiling the back is going to cause a failure and he freaks out and tears the engine down unnecessarily. What we should be letting him/her know is that accepted practice is the recommended way of installing dry and why ,such as being able to maintain the clean aspect that is really what it is all about. Clean means lacking any measurable debris being on the shell back when snapped in place that will prevent the shell properly conforming to it's intended bore.It's just that simple.

[hoodeng]

About thirty years ago David Vizard wrote a series of books on 'How to build and modify Chevrolet engines' these books appeared on more workshop shelves and speed shops than i can remember, and were considered a definitive augmentation to engine building practices.

There are numerous mentions in factory manuals of main and rod bearing seat prep, they all say spotlessly clean and there is no reference to lubrication until after the shell is inserted. [do you need photos of these as well?] the fact lube is not mentioned as you see it, does not mean to not include it?.

When fitting wheel nuts there is no mention of grease, so do we grease them anyway ?


Excerpt from Davids book has not been authorized, but i hope he takes no offense in its reproduction.

Do what you are happy with.Back to work.



Clean and dry.

[fabr]

Again,where is the documented info showing an oil film will cause any failure. You can't show it . If the bearing spun ,fretted,whatever, it was not from that evil oil film.

[Kevin Johnson]

...
The point is I have looked and looked for any actual literature that says a film of oil or even a drenching of oil will cause a spun bearing. This IS what you guys are inferring. I have not even found any literature confirming that dry is better. If you guys have it I will stand corrected ...

You are ignoring the fact that clean and dry is the normal dictate. Essentially you are asking for a listing of any possible way to do something incorrectly and what would the signs be to definitely rule out everything else.

There are a lot of things that you can do and get away with.

"This IS what you guys are inferring." Yes, but it is an inference based on empirical science.

It sounds like you are interested in logic. This is not a necessary (term of art) inference.

[fabr]

Now you are grabbing at straws. You know as well as anybody that if oil film causes spun bearings there would be ample anecdotal and documented scientific literature showing just that. Just because the accepted practice (which I do follow myself) is dry doesn't mean any other way is inherently bad and will cause failures. It just isn't the case.

[fabr]

How long has it been considered the "correct way" to install dry? It goes back well before oil was of the quality we have now. I'm 65 and can remember pouring oil into a glass measuring cup to mix 2 stroke gas. There was all sorts of "debris" floating in the stuff straight out of the can. Think that might have something to do with the age old dry back install? I do . Can you even imagine how contaminated oil was in the 50's? Of course dry was always the accepted practice. All that debris will embed into the soft babbit layer but on the back side of a shell it will not compress/imbed and the shell will not fit the bore correctly resulting in the failures from foreign objects behind the shell in that very good link several post back.

[Kevin Johnson]

Now you are grabbing at straws. You know as well as anybody that if oil film causes spun bearings there would be ample anecdotal and documented scientific literature showing just that. Just because the accepted practice (which I do follow myself) is dry doesn't mean any other way is inherently bad and will cause failures. It just isn't the case.

No, I am not grabbing at straws.

I am turning to the scientific/engineering literature on the subject. Trust me, I am not going to spend $30 per journal article and cite multiple articles just to prove you wrong. I am willing to look around a bit (and have) in order to find texts without a paywall. I used to go to the local university library and roam through the stacks. They used to have rows and rows of failure analysis journals -- all gone now.

How long has it been considered the "correct way" to install dry? It goes back well before oil was of the quality we have now. I'm 65 and can remember pouring oil into a glass measuring cup to mix 2 stroke gas. There was all sorts of "debris" floating in the stuff straight out of the can. Think that might have something to do with the age old dry back install? I do . Can you even imagine how contaminated oil was in the 50's? Of course dry was always the accepted practice. All that debris will embed into the soft babbit layer but on the back side of a shell it will not compress/imbed and the shell will not fit the bore correctly resulting in the failures from foreign objects behind the shell in that very good link several post back.

Well, I am 60 years old now. Yes, I can imagine the problems when detergents were introduced because my Father was a research chemist starting back in the 1950s and I got off my butt and read Consumer Report articles from the stacks going back into the 1950s.

I am not willing to buy a Merlin overhaul manual (they are available).

I tried looking up the NACA MAGiC site but it is down for maintenance at present. I don't feel inspired enough to dig through the NASA Technical Server right now.

[fabr]

Sounds like you are tapping out. I can accept that.

[Kevin Johnson]

Sounds like you are tapping out. I can accept that.

Honestly, I have the sense that you need to brush up a little on the physics.

[FC-Pilot]

So when cleanliness is the key, what advantage is lubing the backs? I have done lots of things “wrong” and had engines live. Does that make it right? Am I then wrong for later doing it the right way? Do I start using trans fluid on my flat tappet cams just because it does not say not use it? I spend tons of time making sure my cylinder bores are clean, why not spend just a bit of time to make sure the bearings are just as clean? I still can’t understand why this thread is so long.

For me it is simple, it is easier to keep my bearings clean when they are dry.

Paul

[fabr]

So when cleanliness is the key, what advantage is lubing the backs? I have done lots of things “wrong” and had engines live. Does that make it right? Am I then wrong for later doing it the right way? Do I start using trans fluid on my flat tappet cams just because it does not say not use it? I spend tons of time making sure my cylinder bores are clean, why not spend just a bit of time to make sure the bearings are just as clean? I still can’t understand why this thread is so long.

For me it is simple, it is easier to keep my bearings clean when they are dry.

Paul

Bingo! I believe that is the only reason it has become the universally accepted practice. It does not mean an oil film will create or prevent anything.

[Kevin Johnson]

So when cleanliness is the key, what advantage is lubing the backs? I have done lots of things “wrong” and had engines live. Does that make it right? Am I then wrong for later doing it the right way? Do I start using trans fluid on my flat tappet cams just because it does not say not use it? I spend tons of time making sure my cylinder bores are clean, why not spend just a bit of time to make sure the bearings are just as clean? I still can’t understand why this thread is so long.

For me it is simple, it is easier to keep my bearings clean when they are dry.

Paul

Bingo! I believe that is the only reason it has become the universally accepted practice. It does not mean an oil film will create or prevent anything.

My old friend used bacon rind and sometimes oil soaked leather belts in place of babbitt before he migrated from the Indian Nation to Cali in the 1930s. Worked too!

A lot of pre-war parts were shipped smothered in cosmoline that would need to be stripped. Seems like someone in AZ did brake testing and those rotors need to be cleaned in order to have reliable and reproducible friction coefficients.

[FC-Pilot]

On the flip side, there very well may be data showing dry is better but I don’t have the time to find it. I know what does work, so why question it. There are plenty of other things in the engine to question in the quest for performance or longevity. I could imagine heat transfer could make a difference, but like I said I don’t have time to find that data.

Now for the sake of our sanity, I am tapping out.

Paul

[fabr]

Sounds like you are tapping out. I can accept that.

Honestly, I have the sense that you need to brush up a little on the physics.

Honestly,I feel you are an experienced builder that cannot prove your case with anything other than "that's the way it's always been done". If you have the physics evidence show it.

[FC-Pilot]

Seems like someone in AZ did brake testing and those rotors need to be cleaned in order to have reliable and reproducible friction coefficients.

Nice. If it were not being involved with vehicle testing I would never have believed all the variables that can skew the test results. Because of that I rely on what the parts suppliers recommend.

Paul