Adding Oil On The Back Side Of Bearings During Engine Assembly. Good Or Bad?

In today's video Jay goes over how he puts bearings in engines he builds. During assembly Jay adds a small amount of oil on the back side of the bearings for several reasons that you will learn today. This is something Jay has been doing for many years. We have received several questions on our previous video ( • Shaving 16lbs Off 2JZ ... ) and we have this video here for you to get a in depth look into why, what will happen, is it the wrong or right way to assemble an engine and some tips along the way. This video explains it all. Thank you for watching! Don’t forget to Click SUBSCRIBE & turn on post notifications, click the bell 🔔 icon
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[@pauldeane9849]

45 years ago I used to work with a guy who oiled the back of bearing shells. We all gave him a hard time about it, and I guess someone must've taught him to do it that way. None of his engines failed, it was just different to how the rest of us did it.

[@8145dwerdna]

It's going to make its way there behind it regardless. lol.

[@thomasleclair7418]

@@8145dwerdna ,,damn true.............capillary effect or action in the hot engine draws oil everywhere............

[@markherring3513]

Did he use regular engine oil? Im about to attempt this on my car.

[@broke_dongle]

He said ATF.

[@jasonmurdoch9936]

Agree

[@matthewbattie1022]

My problem isn't slippage, you are correct that compression takes care of that. The problem with oiling the back of a plain friction bearing is that you actually add a minute amount of substance to an area where the tolerance should be zero. It probably isn't enough to effect most engines, but it's measurable and it's something to consider. I was taught by an airplane mechanic to always clean the front of the journal on caps and engine until completely free from oils, and to do the same with the back of the bearing. I have never had a problem with seating an un-oiled plain bearing.

[@donziperk]

That was my first thought when I saw this.

[@adamminogue9162]

❤😮😅9pm I f9 7th😊😅😢8 5:13 9

[@billjenkins3699]

Dumb idea and a failed explanation! This definitely takes up space and does tighten the brg clearance Of course, he has to chide anyone who doesn't tow "his line: on "his" post..

[@donziperk]

@@billjenkins3699 Is that you Grumpy, the legendary drag racer.

[@billjenkins3699]

@donziperk nah, real the grump passed

[@marttimattila9561]

Occupational school in sixties in Finland we were taught to oil back of the bearing shells, done that ever since. Thanks to the good video.

[@treetrimmerguy2]

Was told years ago by machinist. Oil on the back side of bearing will change clearance. Have never oiled backside. Have never had a problem installing bearings. Have also had good luck with engines I have rebuilt. So I am going to stick with no oil on back side. But plenty on the correct side.

[@realstreetperformance]

Thanks for sharing

[@ACommenterOnYouTube]

Yep the guy that built my motor back in 2000, Dennis at Auto Machine in Orlando Fla (Jay may know the place) told me to NOT oil the back side ... this guy had a huge reputation here in central fla for his building skills.

[@rebbulldesertduke]

As a machinist I'm telling you right now that oil on the back side of the bearing will change the clearance. Also if more oil is in one spot than another on the back of the bearing it will cause hot spots on the journal side of the bearing. Think about it, what's the typical clearance of a main or big end bearing? 0.0025 and you are smearing oil on the back side taking away some of that clearance. Oil does not compress, it's hydraulic.

[@mervynsweeney2948]

Iv always been told to leave it dry, you can only compress the oil so much and could result in incorrect torque and clearance. Bt each to there own, and if it works for you then fair play

[@ACommenterOnYouTube]

@@mervynsweeney2948 well if they are building 2000 hp 2JZ's and none are throwing any bearings, then i guess his method works.

[@soulcapitalist6204]

I'm impressed by seeing it expel the oil on compression. I have changed bearings and learned to put them dry but there's oil back there one way or another after the engine has been used. It's never dry on disassembly.

[@donziperk]

I think it gets the from the oil gallery holes.

[@wlrottge]

​@@donziperkthermal cycling and wicking due to capillary action

[@donziperk]

@@wlrottge More technically explained but yes.

[@flipflapflop2985]

Straight to the point, no filler, no annoying anecdotes or personal stories that don’t pertain to the subject matter, and clear terminology. These videos are a breath of fresh air in a world plagued with terrible content. Thank you for these, and please keep them coming.

[@user-mu1rw1qr2u]

Tell me have you ever stripped an engine and found the back of a bearing bone dry,🤷‍♂️

[@martinrodger9565]

Jay straight communicates his experience. This is a massive gift to us. I’m sold given how hard Jays builds are used and that he gets to forensically pull failures apart. He’s open to others experiences, not preaching.

[@SloppyMechanics]

exactly not sure why people wanna argue with the dude LOL

[@realstreetperformance]

Thank you!

[@PhaseConverterampV]

I work with industrial hydraulic components, and build cylinders. Oil will flow anywhere water will flow, even though the viscosities vary marginally when hot. I’d guess if assembled dry, it wouldn’t take long for oil to get behind all of the bearings, capillary action. There is always space for oil to flow if there is no mechanical seal ( oring etc) Great vid.

[@jeffreydurham5342]

@@PhaseConverterampV I've been in this field for over 50 years and I've never seen a bearing that had been run that was dry on the back. Oil it or don't, it's going to get oil in there.

[@duygukayhanisaskank4915]

@@realstreetperformance I'm new to your channel & now binge-watching your library of KZbin Videos. I've developed respect & appreciation for you. I especially appreciate ALL of your valuable tech tips. THANKS!! I have a simple...but sincere...question. QUESTION: What are your thoughts on using engine oil rather than trans. fluid? Do you think engine oil would be too heavy for coating the bearing backs? I would prefer to use engine oil on the back of the crank, rod & cam bearings. Most of my engine builds are Pontiacs; 389, 400 & 455 & a few BB Chevy. Best regards, Ben

[@speedacademy]

Great info. Thanks so much for explaining all this will definitely put it to use on our next engine build.

[@chrisandtori9083]

I am a race shop/Dyno shop owner and engine builder/ race engineer that specializes in building Superbikes WSBK spec $140k+ builds spinning in excess of 15,000+ rpm’s as well as big turbo setup supercar builds to regular evo’s etc and can confirm 100% that Jays method is not problematic whatsoever. Everyone on here fails to hear the words trans fluid being used which by design is extremely thin and actually almost grippy by design, that squishes out about 99% of the 2 micro drops 💧 out of the side of the journals and act as a transport vehicle or secondary insurance that any possible debris will be carried out with it. Which will in fact happen as intended by the very well rounded and world renowned engine builder (Jay) and this is literally intended to help the bearing shells rotate and evenly settle at the parting lines evenly… this is a good method and works flawlessly from PERSONAL EXPERIENCE on some of the highest strung 15,000+ rpm 240whp+ superbike engines that run at full throttle almost 100% of the time for 40+ minutes at a time… so AGAIN this is a tried and true method, if it doesn’t suit you on your build then discard the advice or dont and use it… either way it’s not problematic either way, but without this tip you just need to be 1000% certain surfaces are clear and installed without backing material behind the bearing as well as using a straight edge and pre aligning the shells as evenly as possible. But this method is great as it allows the bearing shell to locate in it’s intended position without the risk of misalignment and binding if not rotated perfectly level. Thx for sharing Jay, and I don’t blame you when you never share another real world engine building tip or secret ingredient to your successful sauce again. Lol you’ve got to remember Jay your just talking to a team of ex F1 engineers and they should be giving you tips 😂🤦🏻‍♂️. Carry on Jay, building world record breaking 1st’s , and keep innovating and pushing the envelope this is how we grow and achieve that which hasn’t been yet! Take care man!

[@jdmtechllc6589]

Sooo Dexron VI or Type F?

[@ruddyrid]

💯

[@br1_deadpedal]

Positive

[@jamesnoz]

Great video. Always good content. Well balanced discussion on the topic. Can't wait to see the tear down of the 96mm 2jz engine.

[@Seeeeyaaaa]

I'm so glad to see this posted, for years I've been terrified i was doing it wrong if i put oil on the underside of the bearings, especially in the crank main tunnel. I'm assembling an B18C1 at the moment and i'm going to do it per the instructions here and not worry about doing it that way in the future.

[@h2kfabrication192]

So thankful for the videos you post. They are worth so much for us guys that don’t have a mentor to guide us through the learning process.

[@Motor-City-Mike]

Never have in 40yrs. of engine building, never will. My work has seen use at over 8000rpm for two plus hours at a time and never has there been any bearing issues. Fact is, I use acetone to clean the back of the bearings and the bearing bores. Oil between the bearing and the rod/cap/main web creates a heat dam (by becoming a carbon layer) which reduces the ability of the bearing to shed heat. The reason main and rod bearing bores are honed to finish size is to create the cross hatch finish that combined with the proper bearing crush all but eliminates the possibility of a spun bearing - the LAST place you want lubrication is the back of the bearing.

[@realstreetperformance]

Thanks for the feedback Mike!

[@MrTheHillfolk]

Another thing to watch for is if you scrape the backside of the bearing while dropping it in. It's tricky to get the right feel for the squeeze you wanna give the shell to minimize that , and you don't wanna overdo it and bend it. If ya felt ya scraped it a little , see if the sliver/curl is still on the bearing. Remove that with a little blade or scraper or it'll affect the clamp on the bearing. Just a little doodad I learned from an old timer long ago.

[@juanrodriguez-ry6yt]

i am 67 started at 17 l1 master car and truck so i have done a few engines in my time and you took the words out of my mouth

[@Motor-City-Mike]

@@MrTheHillfolk good comment. I break all the sharp corners on the block, rods, and caps. Nothing real big, I just use a 320 grit stone and round the sharp edge. I'm one of those guys that checks every part that goes in - even open up brand new oil pumps. It's just how I was taught.

[@Motor-City-Mike]

@@realstreetperformance Absolutely. We all have methods we're successful with, as long as the end result is the same we're good.

[@sargepent9815]

I rebuild engines as a profession and I use assembly lube on both sides on every engine I build. Specifically, I put it on the lower bearings, place crankshaft, lube the top of the crank, then put the other side of the bearing on, then spin the crank by hand slowly 2-3 turns. After thousands of builds, its never done me wrong.

[@ryanalden7793]

I was worried I'd have tear down my motor I'm building. I did the same. Assembly lube on both sides of all my bearings (crank and rod). Not much on the backsides, just a thin coating to help them seat. Glad I'm not the only one who does this.

[@yavz7565]

Genuinely asking, what would be the name of that profession? Small engine mechanic? Machinist/ mechanic (considering honing and decking)? I’m an apprentice rn and I think I’d like to pull and rebuild engines all day further down the road

[@markthegunplumber8376]

Same here, was an oilfield mechanic for 24 years and used light oil on the rod end to hold the bearing during inst. i rebuilt anything from Cummins and Detroit Chevy Ford Mopar Pontiac and MG and Sunbeam and Austin-Healey. kinda like all the idiots that have real problem when it comes to ring orientation if you don't think piston rings walk around in the groove while you are driving you're daffy, orient them however you want when you pull them many miles later you'll find out they didn't stay where you put them. There is never just 1. way to do things as soon as you think that, some person will walk up and show you a new and better way to do something you didn't think of. @@ryanalden7793

[@Built_it_by-alex]

Been rebuilding engines a while and never did that. Thank you for the knowledge, I really appreciate it

[@Brother2Jis_27s4]

I was taught to keep it dry during assembly for measuring and for final assembly. I was taught in a tech school and the theory is right. Your measurements with a dial bore gauge and micrometer will change ever so slightly if you add the thickness of the very thin layer of oil into the measurement, regardless of the oil type being used. That being said, if the experience of an industry expert says it apparently doesn't matter then I believe him. Keep up the solid work🤙 I was the one who asked what your personal future project plans are for Bonneville when you were on the sloppy radio show✌

[@nobodynoone2500]

In the interest of science, try mic'ing one both ways. It will be a month till I'm that deep in an engine again, or i'd do it. I suspect the oil film will evacuate the high spots, making little difference when installed. The key point he drives home is the low viscosity, so seems reasonable.

[@jeffreydurham5342]

I very seriously doubt you'd any measurable difference.

[@jeffreydurham5342]

see

[@Brother2Jis_27s4]

I agree, but I've seen it documented in many different books that it technically changes your measurements. I've never done a side by side myself but next time I get a chance to I'll find out for science. My dial bore gauge reads extremely accurate and I wonder if it may show me something. My opinion, I highly doubt it would make a difference in bearing clearances in an operating engine if you assembled it wet or dry. And with spinning a bearing, same thing if the machine work is on and the bearings fit correctly or close to correct I definitely dont think it would ever play a role in it spinning. To loose of clearances or not round would definitely effect it, and adding a lubricant film would probably aid in it then.

[@bman1655]

@@jeffreydurham5342I would agree with you but then we would both be wrong, it is measurable.

[@octagon_009]

Thank you for sharing you knowledge with us dummies 🤙🏻🤙🏻

[@jamesjansen8386]

49 years experience, diesel ,gas ,air and liquid cooled . Always installed clean and dry [NEVER used scothbrite] Oil pressure hydraulics bearing and aids in seating the insert to its bore. [Upon disassembly I have witnessed both dry and oily backsides of insert ] This is determined by RMS of surfaces left after machine work and is perfectly acceptable wet or dry . ALWAYS ASSEMBLE WITH BACK OF INSERT CLEAN AND DRY.

[@seankimbrough8489]

I think I'm gonna go with Jay, he's more up to date with the information.

[@just_interested1]

No

[@strokinbaby965]

​@@seankimbrough8489jay also doesn't know the difference between over and undersized bearings if you go watch that video.

[@briggsquantum]

I have always done as you do, install dry and clean. Smokey Yunick stated years ago that he cleaned the surfaces with acetone or lacquer thinner, but never explained exactly why. Probably something to do with the bearing conforming closely to the surface of the cap and block during assembly. But I'll continue to install bearing shells dry.

[@steveashcraft718]

@@briggsquantum , Smokey was one hell of a mechanic.

[@tommyschreiber6883]

100% agree I've been rebuilding 4G63 and 4B 11t engines for 10 plus years I always put oil on the backside of the bearings my machinist wants it done this way and has been doing this since the 60s!🇺🇸

[@markherring3513]

Just regular engine oil? (Im about to do this on my car in my driveway)

[@Alexbuilt]

End of the day as a engine builder do what works best for you and your customers. There's many ways to do the same thing and get good results. Never hurts to always learn more! Definitely made some good points as I did question this when I first saw it.

[@IRONHEAD12701]

My uncle taught me to clean new crankshaft bearings with copper scotchbrite or chorboy. Then lightly coat them with STP, Marvel mystery oil, or mineral oil. He was a great mechanic. 60+ years in the car repair business, lotsa happy customers too. Thanks for sharing🇺🇸 the video post and best 🍀of luck 👍🏼

[@george1la]

Great information. I will use this trick tomorrow when installing my main and rod bearings. Knowledge is Power.

[@_..-.._..-.._]

It’s funny, I grew up around shadetree mechanics and as a kid, I heard about “spun bearings” and engines “blowing up” and now at 35, after hundreds of various engine builds for everything from lawnmowers to skidsteers to Subarus, I’ve never spun a bearing or blown an engine. Old timers were superstitious. My dad thought any engine would “blow up” from sustained revving until he rode in a boat with 2 turbo LS engines that made 700hp each and would run at 4,500 for hours on end.

[@bigbelconut]

I have been building engines for 40 years. I have worked for some of the biggest and well known engine builders. Keith Black, Mondello, Reath automotive, none of them ever oiled the back of the bearing. The cleaner the back of the bearing the better. Oil will hold the bearing off the jurnal, reducing clearance and reducing heat transfer. Not to mention adding a slick surface for the bearing to spin on.

[@jimmillet1442]

Exactly!..all these comments how theres nothing with it but it never hurts to get lucky I guess.My uncle works for Keith Dorton,one if the shops that does alot if nascar work and he told me decades ago you never allow oil on the backside of the bearing,common sense really..but common sense is not so common anymore. You want to those bearings to "stick" to the cap or block they are going in.Oil is never meant to be behind them.Period!

[@johncasor9698]

you need to learn how to spell first... what is jurnal ??? is that a new word for you high tech engine intellectuals ???

[@adambergendorff2702]

great video ,well explained and demonstrated, thanks for posting.

[@beachboardfan9544]

Nice! Appreciate you taking the time to make a vid about this.

[@AWBElectrical]

Had a rotating assembly bind up when one of the guys used assembly lube on the back side of the bearings. We pulled it apart cleaned it all off and installed the bearings in dry and the crank rotated. Obviously this is not oil.

[@realstreetperformance]

Thanks for sharing

[@liftedcj7on44s]

So a trick I use to keep the Parting line of either the Connecting rod or the Main journal from pulling material off the bearing when you put it in is when you are doing your machine work what I do is take a file and put a 45 degree chamfer on the parting line. This keeps your bearing install super clean and no oil needed on the backside.

[@Comet-hn3gm]

Yes. This is also what I have been doing for years. Less or no scraping of the back side. I try to use King Bearings for all the engines I do. Now for the novice builder, remember no matter how clean your new parts look they need to be cleaned and inspected.

[@Motor-City-Mike]

Yes, I do as well. Oil doesn't belong on the backside of the bearings.

[@MrTheHillfolk]

@@Comet-hn3gm if you happen to do a little scraping , it's not the end of the world just remove the sliver off the bearing before you put the cap on. Yeah oops , but it should be ok just don't keep doing it.

[@seanravine6596]

Yep i always soften all the edges easier on bearing install and reduces the chance of having a small burr mess with how the main/rod cap mates to its surface

[@Comet-hn3gm]

Correct.

[@d.i.mdoitmyselfgarage8874]

Thanks for the information. I’m always learning something watching your videos. Great job

[@daledavies2334]

35 year journeyman mechanic here. I use a very fine file or 320 emery on the sharp corner of the bearing bore opposite to where the locating tang goes. Just want to knock the sharp edge off so it does not shave metal off the back of the shell. I do this on both mains and rods. Installing the bearings, I get the tang side in place and push the shell into place dry. The bearing crush pushes the shell tightly into place in the bore to hold it firmly in place. Doing a bearing roll during an inframe overhaul, the tang side of the main bearing bore is smoothed carefully and cleaned out thoroughly, as the shell needs to be fed in from the tang side. Done this many times on 400 Fords and Detroit Diesel heavy duty engines. We all have our preferred methods and whatever works for a person, carry on.

[@Kstang09]

6 one way. half-dozen the other. Cleanliness of all parts + correct/gentle install is much more crucial.

[@wheels-n-tires1846]

Am suprised by this... Ive always gone with super clean and dry, always watching for those lil shavings. Cant say Ill ever change that, the physics say its a bad idea, but hey, if you have a successful track record- keep doin what youre doing!!👍👍

[@kentuckybowl-o-sticks]

Yep... it's much easier to insure NOTHING is stuck to the bearing or bore contact surface if it is DRY... in fact, the oil will tend to attract and CATCH debris.

[@zdravkomomci7570]

​@@kentuckybowl-o-sticksI agree having oil on back of a bearing will change the clearance in the tens of one thousands and could interfere with heat transfer, that backside film when burnt from heat could create bearing move or walk from loads imo.

[@kentuckybowl-o-sticks]

@@zdravkomomci7570 Yep... I can't think of any BENEFIT to applying oil there, so... why cloud the issue? Almost like PUTTING weevils in your cereal : )

[@PGHdrift]

I have done both and great success both ways. Long as your measurements are spot on and do things properly should be no issues. Just like you said need to get familiar with doing it.

[@scubbarookie]

Thank you for these fresh tips. I do appreciate the detailed information, and for this reason, I subscribed. 👍

[@larryfeasel2403]

I've built hundreds of engines over the past 35 years. Have never had an issue without oiling the backside of bearings. Would like to see how much you're temporarily changing oil clearances causing excessive wear on bearings. Will do some measuring on the next assembly just to see. My bet is there is enough for concern

[@alaskanbloke]

yes larry a very simple check is to assemble with both methods oil on back of bearing and without , assemble both ways with plasti gauge and measure the difference

[@tahcogunworks]

flynn plasti gauge is like measuring with a yard stick. Lol.

[@alaskanbloke]

@@tahcogunworks please explain how many engine you have built and your methods

[@daveb1870]

If the oil couldnt escape and was trapped between the bearing and the housing then yeah it would be of some concern. As its not youre talking maybe 4-6 microns and if your worried about that then you got some serious ocd issues.

[@larryfeasel2403]

@@daveb1870 so you have measured the oil layer after the bearing crush ? And it's .00015748 - .00023622 ? Really ? What'd ya measure it with ? How many engines you built? Excluding the Briggs on your mom's lawn mower. How many are still running ?

[@dentwatkins2193]

I worked in Research & Development for Vandervell, the shell bearing manufacturer, building engines for testing on dynamometers and on the road or track. The engines on test beds were subjected to extreme conditions that it would be very difficult or impossible to replicate in use in a vehicle. The test engines were assembled with great care and attention to tolerances and, particularly, cleanliness. They were all assembled with the bearing housings and the backs of the bearings spotlessly clean, degreased, and absolutely DRY, definitely NOT oiled. Care was taken to avoid touching the bearing surfaces, the steel backs of the shells, and the main bearing or rod bearing housings with bare hands to avoid contamination. The bearing surfaces were lubricated once they were installed in the housing immediately before assembly. What they were lubricated with was dictated by the test schedule for that particular engine, but none of it ever went on the backs of the shells. R&D was carried out in two buildings away from the main factory buildings where the shells, thrust washers, and cam bushes, original equipment for many European, Scandinavian, and even some American engines, were manufactured. We had four large soundproof cells in the building where I worked with a total of seven test beds, and another test house in a separate building round the corner with more test beds in cells there. There was also a rig shop where test rigs subjected bearings to excess heat, loading, contamination, lubrication failure, and other abuse. We had a comprehensive machine and welding shop where we produced one-off kit for mounting engines to the beds and dynos, custom plumbing to suit each engine including, on occasion, separate duplicate systems to subject engines to thermal shock and other nasties. (It was handy for producing parts for our own motorcycles and cars during breaks, lunchtimes, and the rare quiet periods too. 😉) All in all, a great job.

[@wlrottge]

I'm going to bet that the bearings were installed "dry" was for two reasons; first, there's a test standard and you have to follow that procedure EXACTLY. Second, I suspect that the test procedure (engine assembly) required dry bearing installation to decrease the potential number of variables that could influence test results. It's easy to quantify and isolate "clean and dry", harder to isolate and consistently say, two drops of oil, ten drops of oil, applied front to back, left to right, big drops, little drops, I lost count of the drops, fresh bottle of oil, old bottle of oil, we didn't use oil, we used antiseize, we used ATF, Dextron vs.... etc. etc. etc. You could spec a procedure that included oil on the back of the bearing, but, like I said, reducing number of variables. I think in this case it had nothing to do with whether it makes a difference or not.

[@nickarmstrong8788]

Great tip! I will definitely use it in the future. Totally makes sense to me.

[@trev8932]

Totally agree with this video, been doing this for well over 40 years.

[@jimciancio9005]

Never went crazy with the oil on the backside, but here's the fact! I worked on my own dozens and dozens of different types of engine, to building all out race engines used for drag racing. Then also in my teens to early 20s worked in a engine machine shop, first as an apprenticeship and towards the end being able to machine every part from blocks to cylinder heads and everything in between. We yes I absolutely agree with you on this topic, every running engine I've ever taken apart has a coating of old burned smelling oil on the backsides of rod and main bearings!!! Especially the mains which have oil feed holes through them which need to direct oil to the crankshaft surface. Being you have a couple thou of clearance between the say crank surface and bearing surface well that oil which is sometimes upwards of 80+ PSI coming through the oil galley hole passing through the bearings hole will absolutely seep in between the main saddle and form a film of oil between the block surface and backs of the bearings. Now also this is also the case with the rod bearings, some are sometimes dryer than others but depending upon clearances you can easily get oil behind the backs of the rod bearings. Does this hurt your engine???? Welp from personal experience and plenty of race engines, never once have a bottom end coming back with a crank, rod or bearing issue or having rods letting go, 🤔 I can say does it really make a difference in weather or not to apply a film to the backs of them?? No!!! Yes wipe them down first like everything else that goes into your engines using a solvent first of course. And my personal preference would be to give them a very light coating of oil to help prevent galling of the backs of the bearings against the sharp edges of the block or caps, absolutely 💯% agree. I tried it dry a few times in the beginning and found it was just easier to get the bearings into place than it was dry, especially the camshaft bearings that are pressed into the blocks on pushrod engines. Otherwise you definitely run the risk of galling one on the way in to its position. 😉 I know when it comes to this conversation just like opinions and assholes, everyone has their own. That's great, and I'm sure this technique will be argued about for another 100+ years. The fact of the matter is......... it doesn't really make any difference. But I went with what made things assemble easier and without damaging the backside of the new bearings. I'm sure someone will definitely disagree with me too, but I know my record on never having a bottom end failure attributed to spun bearings or any clearance issues, having more engines under my belt than I could ever remember now, we never had anyone recalled due to something related to this practice, sorry.

[@johncasor9698]

so what is your point???

[@jangell1320]

@@johncasor9698- Thank you! Someone had to ask.

[@Smokkedandslammed]

That fact that these motors work at all and the power we can get out them is insane in itself, I love it 🤘

[@realstreetperformance]

Couldn't agree more!

[@_..-.._..-.._]

I’m amazed that any engine can have 10,000 20,000+ hours on them, it’s hard to believe how well they work, when I first learned about piston rings at 6 or 7 I didn’t believe it, “you have metal scraping metal thousands of times a minute, and it’ll last for decades?!?” Motor oil is an amazing thing.

[@samsharp8539]

I always use red Loctite or red hi-temp silicone sealer. I should not have written that. No doubt someone will do it. Our IH 806G has some interesting stains on the rod and cap where the shells ride. We always used a thin lubricant on the shells. Our junior-high/high school shop student-teacher taught us that in the 1960s. After getting his teaching degree he ran a 289 in a rail at our local drag strip. The dragster was reasonably reliable… and very fast. His ‘Clutch-Flite’ never failed on race day.

[@thomasleclair7418]

,,,I'm new here.....Thank you for the work , time , and professionalism........At 71 my days of acquired knowledge from builders like , Bill Jenkins and Smokey Yunick are very dated...............Minds like yours keep the craft alive............................................

[@travis7212]

Here come the keyboard mechanics.

[@MalakaMotorSports]

😂

[@youngstah619]

Good one

[@ghoulbuster1]

Experts in writing skills, but nothing else LOL

[@marcusmarcus8616]

What's a keyboard?

[@romainberger]

It cracked me up pretty good, thanks 😁

[@devontrini]

Nice I always wanted to know why you did that. Now I was also wondering since you tightened the bearings to take measurements then loosen and retighten for final assembly do you loose some of that bearing crush? Thx

[@Tony-ib2vm]

Elastically deformed interference fitment.

[@langstonjones69]

Good solid information! Thanks for sharing.

[@davidalvarez5929]

Very informative, interesting topic. Thank you

[@SuperSupra7mgte]

That's why all the big horsepower supra guys go to Jay for engine builds because the guy knows what he is doing. Just ask baltic supra and jrod.

[@369motoman]

I have been building street/racing motorcycle engines for over 35 years. I always use this method of cleaning, using a light oil and light torque of main and rod caps without the crank to align the bearings and then install everything w Torco or Lubraplate assembly lube. Some of the super stock 600's peak power is over 14k rpm and they see that all day long at the track. Also I have never seen an engine taken apart where it didn't stink like burnt oil when you pulled the bearings, damaged or like brand new. Cars, trucks, tractors, or motorcycles, so oil is always under the bearings.

[@ae70gts]

im a car mechanic . i learned rebuilding engines from my father he is a mechanic since 1969 . he taught me to put a slight amount of 10w oil under the bearings . the reason , he said, is what you said EXACTLY!! none of the engines he built failed and none of the engines ive built failed . the thing is that no other mechanics ,i have conversations with ,do that

[@PLUMPTONFILM]

Thank you for the notes

[@asperf5708]

Thanks a lot , real good explain an shared experience with us, we apreciate thank

[@davidaarons2488]

I put bearings in Cadillac engines for 20yrs at dealership , dry when on the engine stand and when in the car they no doubt got oil on them, never had any issues that came back for bearing problems. If it were my engine they would go in dry than oil, I learned that anything behind a bearing could cause problems. Yes oil gets behind them, the mains through the oil galley hole. I guess I am old school. Jesus Does Save

[@denniswilder3014]

I've been oiling the back side of bearings for years.my shop teacher in high school had a brush inside a old plastic carb cleaner cap on his bench and in it was marvel mystery oil thinned slightly with diesel.and would coat both sides.ive been doing it ever since.when you tighten it down it pushes most of it out the sides

[@ezpz7143]

Then sir you have been doing it wrong from the start.

[@denniswilder3014]

@@ezpz7143 I've done probably close to 200 motors and in the last 10 years they have been turbo motors pushing 40 lbs of boost some supercharged motors and a bunch of nitrous supercharged turning 10,000 rpms banging of the rev limiter on jet skis and they seem to last.im gonna keep doing it till I'm proven other wise

[@alvtuning5877]

3:40 shows the advantage of the lubrication method.

[@jeremyking5684]

But what did the oil do? It's wasting time with no benefit what so ever.

[@denniswilder3014]

@@jeremyking5684 when you put the bearings in like in the video the bearings do slightly move when torquing them down.and as they are almost a perfect fit there is a ever so slight movement.with rotation and heat expansion.exspeacialy in aluminum blocks.and under normal use oil pressure does push oil in between the bearing and the block.

[@moedigzz]

Jay, your bearing prep tips are absolutely essential. Yes, you could just toss some bearings in and end up with a perfectly healthy engine. For the engine builder to be absolutely certain, that everything was installed perfectly, you would need to take the tips you described. Also, ANYONE who says bearings are to be installed completely dry on the backside and/or that the block's bearing housings are to be cleaned and dried before bearing installation just needs to take one used engine apart. They will clearly see that oil ALWAYS finds it's way, behind the bearing shell. IMHO, I have always lubed the back sides of bearing shells before installation. I have never had a bearing shell that needed cleaning with a scotch bright pad. Always wiped them down with some parts cleaner and a clean lint free rag. Then I'd apply assembly lube on the backside. Just a tiny amount and used a clean finger to spread it out to a thin, even coating. Never once had a bearing failure on a single build. I have built about 100+ engines of all types. Not a large number of builds, but enough to know what is important. Thanks for the tip on using a thin lubricant, like ATF. Instead of using a thin coating of assembly lube.

[@morandydacruz5995]

Thank you for the informative advise

[@sparkplug1018]

Curious if you've measured clearances with the lube behind the bearing and without?

[@billjenkins3699]

It absolutely does tighten bearing clearance Don't do this people!!! Be hard headed if you want!

[@1997obspsd]

I see it from both sides, I learned no oil . I'm interested in the clearance differences.

[@radugenis9698]

Last month I ask about this and now see a video. You a the best!

[@themikeanic1535]

I agree. Same method! Got into several arguments w an old boss about it. Never had a failure.

[@treetrimmerguy2]

Also, watch a modern engine assembly done by robotics. Never do they put oil on back side of bearings.

[@caddyrack]

Hello Jay, thank you for your input on the matter of lubrication "under" the bearing shells. I did not hear you mentioning checking bearing clearance with a plasti-gauge. I never use them right-out-of-the-box unless I check clearance on mains and rods. Having oil under the bearing it will give me a 'false' reading, I do all the plastic-gauging and then remove the bearing and put plenty of the best bearing assembly lube available on the face of all the bearings. Even though I measure all the rods and mains with a dial bore indicator before I install them, I'll make sure all my number are right on. Sorry for the length on this, I don't disagree with your method mine is just slightly different. Thanks again on sharing your knowledge. All the best to you.

[@ElT1greVerde]

so much good information and awesome explanation

[@ChuckPahl10]

very interesting stuff jay.quick question when you are cleaning the back of the bearings is there any type of fluid you use and what type of cleaners not to get on the bearings surfaces?

[@SloppyMechanics]

"i have a, pretty good track record on success, as far as putting engines together and not having them fail due to assembly error" always humble

[@ArmoTypeArt]

matt you made me giggle lol

[@TrojanLube69]

And make over 900 whp on stock components including re using head gaskets and torque to yield bolts. A true legend of the masses. We love you sloppy.

[@austindoud273]

Hey mat remember the 240 lol

[@DBLDREW]

this video would be more convincing if you compared a dry vs oiled bearing with a bore gauge to see what the change is between both

[@thecarrepairdummy7021]

thats key, it works for sure and i wouldnt doubt that considering there are tolerances, and if its out of tolerance or very close within most times itll lightly self clearance and become non issue. but then after a while, that oil will be gone and your clearances would be higher. from my perspective it would be ok to do, but its maybe 25% maybe more, of cases the engine will not last as long. By then something else might have failed. its all chance

[@_..-.._..-.._]

@@thecarrepairdummy7021pulled that outta your arse 😂 you have a pro builder and randoms are arguing with his technique.

[@_..-.._..-.._]

The oil squeezes out, if you think it’s gonna throw off the tolerances, you’re crazy.

[@thecarrepairdummy7021]

@_..-.._..-.._ was probably drunk when I posted that, honestly it looks like I was rambling 🤷‍♂️🤣

[@MonkeyFabGarage]

Interesting. Good stuff. Thanks

[@cdars1]

Forget about the internet mechanics and builders, i like your way your builds have been proven

[@uzqf2107]

Exactly

[@kylekeck9617]

I was told never put oil behind bearings in fear of oil coaking, burning the oil that isnt being displaced, which in theory will shrink tolerances.

[@bobroberts2371]

I've gone through countless engines over the years and the only time I've seen a main or rod bore get remotely hot was when a bearing hammered out and spun. Bearing bores have a honed cross hatch like a cylinder wall so oil makes it's way through the groves anyway.

[@kylekeck9617]

@@bobroberts2371 the bearing should seat well against the main and rod bore with any clearance to be between the bearing and journal though, there should be no space for oil behind the bearings. They crush at the seams (as the video explains) and I really don’t think the goal of honing a main or rod bore is a similar RA as a cylinder, it’s only used to make it proper size. 🤷‍♂️ I’m no expert but the people I work for claim to be

[@bobroberts2371]

@@kylekeck9617 The bearing bore and back of the bearing are not polished smooth so oil will eventually wick behind the bearing when the engine is in operation. I'm well aware that the primary goal of line honing is to side the bearing bore. My point is the honing leaves peaks and valleys, this allows oil to migrate between the bearing and bore. I don't intentionally put oil on the back of the bearing however, thin oil does not pose any problems.

[@ahmedsimmons4465]

What happens when you take a motor apart and remove the rod bearing? There is oil on the back side right? So what's the harm in adding oil on the back during assembly?

[@1997obspsd]

Change clearances in the beginning,those galleys aren't used untill full assembly then primed. I've never put oil in the back of a bearing due to measuring for clearances but I agree that we should see a video with clearances with and without oil on the back. If it dramatically closes off the clearancing that could be an issue to begin with

[@grantreid3031]

I did an apprenticeship in a reconditioning shop and then a further 20 years and i cant say that the engines i have ever pulled apart had oil under the rod bearings they were pretty much always dry. I learnt all about tunnel sizes nip, crush etc but not to put oil under the shell nor have i ever seen anyone else do it.

[@ahmedsimmons4465]

@@1997obspsd Yes we need someone to do a video on that using two of same motors and bearings. One with and without oil.

[@chadchadwick3380]

No there should not be any oil under bearing when you take one apart if assembled correctly will not be any room for oil to get behind bearing.

[@grantreid3031]

@@ahmedsimmons4465 Common sense tells you that any oil foolishly put under the bearing shell will get squeezed out when the caps are tensioned as the bearings are designed to be an interference fit when the caps are tightened this is where the nip and crush come into play.

[@madeljacky]

I have built hundreds of engines and never oiled the back of the shell bearings on one of them and never had a bearing failure yet either. But when i rebuilt some of the same engines after 16,000 hours on them when i took them apart there was oil behind every shell bearing when i removed them from the block or the con rod. So if you want to oil behind the shell bearings when rebuilding, thats fine. If you dont want to oil behind the shell bearings when rebuilding, thats fine. Whatever works for you stick with it is what i say

[@lornetontegode6986]

Yup, as a Tool and Die Maker myself, there is no way you'll get a smooth and flat enough surface that will seal oil from wicking into the mating area. Absolutely impossible to keep it dry since the honing scratches alone are enough to create tiny gaps.

[@tthams73]

You’re spot on! A spun bearing only occurs after excessive wear. Once the tolerances from the wear exceed a certain point catastrophic failure can occur. However, the bearing failure occurred before it actually spun.

[@zdravkomomci7570]

That wear is increased your bearings walk from assembly oil placed on its backface that burns from heat and could turn to extra clearance it shouldn't be there and could loosen up your bearings in cap and saddles also bolts torque settings are altered due to extra clearance created on bearing backside I'm talking in tenths of a thousand

[@genemartin6962]

I am with Mike below. you cannot get the bearings and rod too clean. I use lacquer thinner to clean everything. the heat transfer is critical from the rod rotating end. I have never lost a rod and have built dozens of high rpm engines. it may work for you but I will never, ever build an engine like that.

[@_..-.._..-.._]

Which side are you on? You start off seemingly agreeing with the vid, but the end sounds like you disagree?

[@markwallace5274]

Never oiled the back of a bearing before always just clean them really well but I’m open to trying it on my own personal engines. If it works for Jay on the high power builds he does I’m pretty sure it’s okay to use a really light oil on the saddles anyways Would love to see more on that B20 build I’m sure it’s been done and running but hey can’t hurt to ask right ?! 🤷🏼‍♂️

[@user-du1mz5zx7s]

Exactly, just clean/inspect the mating surfaces very well.. I’ve gone as far lightly rubbing them with a tack cloth..😆

[@fredcarpenter1027]

Thanks for the info. Some don't lube the back of the bearing, which didn't make sense to me. Thin lube definitely makes sense

[@caluzzucarrazzi5549]

At the end of the day i think extra steps like this provide good piece of mind

[@boosted2.4_sky]

If it makes you feel good and it doesn't hurt anything.... do it!🏁

[@boosted2.4_sky]

@@AZDESERT2024 yeah.... wonder how many engines of Jay's have blown....🤔

[@petersomers3014]

I agree with this method. Nice to see some one else doing it. I have been looked at sideways when I have done this method. My father was an engine builder in the 60's-80's. This was his tip to me on the first engine I ever built. Great work Jay. Love these info vids. Keep it up crew!!!

[@realstreetperformance]

Thanks for sharing

[@connieahren3841]

I appreciate your knowledge thanks

[@ymperformance]

Great info! I can see it from both sides

[@ricknolte6846]

We used to rebuild NTC-855 Cummins diesels in the frame. You would do one main at a time and we would clean as best as possible, then roll the top main bearing into place around the crank, install and torque the cap and done. These would run 350-400k miles with no problems. While they didn't turn 8000 rpms, the pressures in a diesel are considerable under load.

[@altruismfirst6489]

I saw in Thailand workshop that in frame they wipe mains with clean rags then spray clean diesel onto the mains cover with rag for an hour before putting on the bearings in. Its hot there and they abuse all things that move but just wondered if this was done by others?

[@luciankristov6436]

Ive never known anyone who spun a bearing from putting oil on the backs of the bearings...ive never once had a problem. To each thier own

[@clarencetrinidad9149]

Hello Jay, I appreciate these videos you have put out. They have been very informative. I wanted to get your input since I'm no professional mechanic but have some experience. I'm replacing the rod bearings on my bmw s54 engine which happens to be a maintenance item due to the narrow size of the rod bearing. Would you saw this process can apply to a used running engine as opposed to a new assembly in your video? Not sure if it makes a difference that the s54 has a forged cracked rod. Would using scotch brite on the rod surface be ok? Thanks!

[@isuzooms]

Excellent video!!

[@marshalleng1933]

I always learn something from these videos! Yet another great educational video

[@realstreetperformance]

Glad you enjoyed it!

[@3vcobrajet815]

Why not put oil and wipe it off just making it a slippery surface, so it wont effect the clearance as mentioned by experts in the comments. Thank you for sharing your knowledge 👍

[@TheClintmeister]

Many years working with engines and I have never heard anything like this. Thank you for educating me, Very good info.

[@wymple09]

Like this guy, I have always oiled the backside of a bearing with a thin oil on assembly. I've never spun a bearing although I stuck to stock engines not heavily modified. I doubt it makes a difference, but that's what I did.

[@kesterbrowne4318]

One of the most humble engine builders who has proven success with different engine platforms. Great job Jay thanks for the lessons.

[@realstreetperformance]

Wow, thank you!

[@richardcranium5839]

i was taught 40 years ago that 1) oil takes up space 2) why would you lubricate something that is meant to be a friction fit? 3) the bearing manufacturers have instructions for a reason follow them.

[@markthegunplumber8376]

If your theory is true i didn't need to buy +.001 bearings for my new crank i could have just greased the back side of them them. Damn i could have saved $40 on main bearings. If bearing clearance is generally .0025" how much you figure a thin coat of 30 wt. oil will make up. when i disassemble engines the rod end under the bearing has oil in there. wonder how it got there?.

[@wlrottge]

​@@markthegunplumber8376it's because the oil freezes once it gets behind the bearing shell and no longer behaves like a FLUID anymore, duh (that was sarcasm, I agree with you)

[@squirel6025]

Excellent info sir

[@Not2day-Satan]

This makes total sense. I wonder if when going dry, stuff behind the bearing will embed and effect the clearances on the other side of the bearing? I mean oil eventually gets back there. I like his hydraulic flush explanation, very insightful.

[@ACommenterOnYouTube]

2:00 I kinda see your point there. Putting the oil on the back side allows the bearings to move into proper place as the cap crushes it down. And as you torque it down, we can see the red fluid being pushed out along with the black stuff. Kinda like how window tint is put on with soapy water, they dont put the tint on dry OR when you 1st drop the piston down the cylinder wall, they say to rub wd40 on the cylinder wall so that as the piston is dropped in, the rings dont "scrape" the wall, the wd40 acts as a barrier to allow the piston to smoothly drop in without scrape. So, where as normally we do not put oil there and therefore we are putting a dry bearing surface to another dry metal surface, then as you tighten down the cap, you have 2 dry metal sides being pressed together and if there is a slight mis-alignment, now you potentially have a scratched bearing or crank or rod side. The question i have, IS all the red stuff being pushed out or is there some left under that bearing which CAN cause an issue like everyone is seeing as a thrown bearing .. ?? The video shows the red fluid being pushed out, but is all of it being pushed out ??

[@budlanctot3060]

This reminds me of a HS physics experiment, where we had sheet pan full of water. We sprinkled talcum powder on the water's surface, then dropped one drop of oil from an eye dropper to the water surface. The oil would spread out over the surface, displacing the talcum, so you could easily see and measure the diameter of the circular patch of oil. Knowing the volume of oil in one drop, and calculating the area of the circular patch of oil, you can divide the volume by the area and calculate the actual minimum thickness of the oil. Personally, I will agree with the cleaning the back side of the bearing shell, but I think I'll still refrain from oiling the backside of bearings.

[@montinaladine3264]

Great video thanks. Awesome close HD shots and clear explanations really makes lots of sense to me. Plus no razzamatazz stupid music added in was a bonus.

[@TaekwondoFitForLife]

“Absolutely, attention to details are key”😊

[@RHBTurbochargers]

I like to do final assembly with the bearing backsides dry. But I agree it all comes down to crush. Similar to a press fit component, oil there won't matter. I've even seen people use tin foil or newspaper on a back side to tighten up a clearance. If you spun a bearing because of a bit of oil on the back of a bearing you had a major issue somewhere. Important to remember that mains on some engines have oil pressure at all times behind ~1/3 of the bearing width too.

[@donwest5387]

newspaper won't transfer heat

[@jimclarke1108]

I'v never put oil on the back of any bearings, found many engines with dry bearings on disassembly

[@nsboost]

Dumbest comment of the year award. If a bearing didn’t have lubrication it has nothing to do with assembly. That’s a deeper issue.it would have failed immediately if it didn’t have lubrication for any amount of time.

[@jimclarke1108]

@@nsboost Talking about the back of the bearing fkwt

[@jdubcbr600]

Great info!

[@doneB830]

40 years doing engines and fit dry on the back when rebuilding but I have done hundreds of top and bottom rolled in mains and also never had a problem. Maybe I will mic some one day but I think either way is fine.

[@ChielScape]

It doesn't cause any problems. It also doesn't solve any. I've worked on numerous reciprocating compressors and a couple engines, and watched our mechanics do many more. Some lubricate the backside, others dont. Guess what? Absolutely zero difference, despite how tight a bearing clearance our machines run. Wiping a bearing back with a clean rag is enough to clean it. Anything more than that I'm afraid is a superstitious ritual. The fact of the matter is things just arent quite as sensitive as people have been lead to believe. It's the same with how paranoid people are with balancing crankshafts down to the precision they do (on par with high speed turbine/jet engines/turbochargers at up to and over 100k RPM) when in reality, engines don't spin fast enough to warrant that sort of precision (in fact, crankshafts in particular will always have an alternating imbalance due to continuously varying rod angularity that is several orders of magnitude larger). Now if it makes you feel better or helps with a neat, clean workflow, as I mentioned, it doesn't hurt anything either, so have at it.