Lubricating the backs of bearings

[ACM]

Hello folks-for years I’ve been told to never lubricate the backs of bearings as this would cause untold issues with the engine being assembled and this has been echoed by industry experts as well.

Here is an interesting take as to why in fact you should be lubricating the back sides of bearings.

Https://youtu.be/yAt-fkTntjE

Basically he states that lubricating the backs of bearings with a light oil will flush out any contaminants when crushed into place.

Let me know what you all think about this.

Thanks everyone and have a great day

[fabr]

I built a lot of mild to wild engines over 20+ years of running a perf machine shop. Admittedly,the last ones I did for others was 20 years ago but I always wiped the saddle and bearing with acetone and then applied a thin coat of whatever engine oil was being used in the engine. My theory was it couldn't hurt and it would help initial heat transfer. Every engine I ever tore down damn sure had a thin film there...............

[Dave Koehler]

will flush out any contaminants

Balderdash
There should be NO contaminants on assembly. He's fired.

[hoodeng]

Some years back an aircraft engine failure was partly attributed to the incorrect application of anti-seize lube on the backs of bearing shells.[This was clearly a overuse situation].
The subsequent crash was the culmination of an unlikely chain of events involving both engines failing within a short period of time of each other.

Clean and dry.


https://www.atsb.gov.au/publications/in ... 02157.aspx

[Momus]

Both surfaces cleaned with solvent, dried and assembled.

Lubricating an assembly that is relying on an interference fit for it's function makes as much sense as greasing the soles of your shoes.

[fabr]

Some years back an aircraft engine failure was partly attributed to the incorrect application of anti-seize lube on the backs of bearing shells.[This was clearly a overuse situation].
The subsequent crash was the culmination of an unlikely chain of events involving both engines failing within a short period of time of each other.

Clean and dry.


https://www.atsb.gov.au/publications/in ... 02157.aspx

Anti-seize is full of very fine "grit". Engine oil though has none of that. That is unless your hands are dirty when applying. I've seen plenty of shade tree types use Loctite on the bearing shells and that stuff sure as hell takes up some clearance. There will be a hardened layer of it on the bearing back or the saddle upon disassembly. That makes no sense at all. I still fail to see where a drop of clean oil spread on the back of the shell can do any harm. Enlighten me please.

[jeff swisher]

I have heard many odd things over the years.

I have a 1969 300HP 350 that has over 400,000 hard miles on it.
I got it with 100,000 miles on the engine.
I stuck new pistons into it and new rings and bearings Moly faced E251K rings.
I did not touch the cylinder walls with any hone. I just left that 100,000 mile glaze.

Rings seated instantly. Bearings were FM brand and stuck in dry and clean and then I applied some lube to them.

Crankshaft was never turned Never polished ..it was as is from GM.

70,000 miles in a 78 Nova in 1 year.
Then pulled and sat and then I pulled it apart and new pistons and rings again and new bearings.
It went into a 47 Dodge truck

No hone and crank never touched again.
Bearings looked like I removed them from the box but I stuck new ones in it anyway.

6+years later I pulled it and freshened it for the last time ..New pistons NO hone new bearings again and new vehicle a 1957 Chevy.
Been in it for 6 years I average 30,000 miles a year and pull trailers and my Pontoon boat with it.

This thing sees 7000 rpm on a daily basis and there is Zero wear in the cylinder walls and the standard bearings always look excellent no scratches
no grooves just a perfect bearing.

NO lube on the back side of the bearings is a must.

I did a test on lubes and rust.
I took a 3 foot piece of flat steel and sanded it and tried different engine oils, wd40, 2 cycle oil, Kroil and some transmission fluid.
I applied these oils in separate sections on the bare sanded steel.
Steel was set out in the elements.

Engine oil was Mobil1 synthetic and it rusted quicker that the other lubes.

Now what passes through my mind is this oil behind the bearing shell does not get to be removed and freshened up.
It gets to stay there and cook and break down.

If a guy was liking to experiment with things i suppose you could stick some oil back there on your personal vehicle and flog it for 150,000 + miles and see how it turns out.

With well over 400,000 miles on my 1969 engine and being standard bore and standard crank I will stick with what works for me.

Here is that little 350" in my 57 chevy getting flogged and it gets this often. Points bounce at 7000 rpm. Off the shelf single point distributor Sorry .


https://www.youtube.com/watch?v=c_rpV3Z7iFE

[Dave Koehler]

The modern engine does not use free floating bearings. As mentioned the bearings depend on a press fit condition.
The 1948 flathead ford was the last or near the last to use that method

[rebelrouser]

I do not want anything on the back side of the bearings, oil or dirt, I want the bearing locked to the caps, rod or main. Everything gets wiped with a light oil until the towel comes clean with oil only on the towel before assembly, cylinder walls and journals, I have always been anal over the years about that process. Wipe oil on the backs of rod bearings, plastigauge, and then wipe the oil off and plastigauge, post the results.

[Kevin Johnson]

Try to encourage a graduate student to explore an interface model employing a lubricant as their thesis subject.

http://web.posfemec.org/posmec/14/TRB/TRB1446.pdf

https://www.researchgate.net/publicatio ... iction_law

[Adger Smith]

Remember: ATF isn't really oil...Just one of the things he botches up in his demo.
IMHO Another You tube Expert that is defying the laws of physics. SMH
If that works for him He is just a lucky dude..

[BOOT]

Dry & Clean is what has worked for a long time. I think if countless engineers changed to wet, then I'd also give it a shot.

That's why I always try and say "My Opinion" or something like that, in my videos with this type of stuff. Still I didn't watch the video, just clicked the link to see who it was and I'll chalk it up to maybe there is something happening he don't realize.

[1980RS]

If oil film is to cushion the bearing on the crank surface, why in the hell would you want to do that on the back side of the bearing?

[digger]

i actually don't think it will make one iota of tangible difference good, bad or otherwise what that guy proposed.

i don't think many actually watched the video based on the comments lol

[modok]

Lubricating the backs of split bearings?
The risk outweighs the benefits.
I'm not saying there is a lot of risk, but there is even less benefit.