Adjusting Babbit Crankshaft Main and Rod Bearings

[CM2]

Note the info corrections to this article starting on post # 30

The following topic covers adjusting the Crankshaft Main Bearing and Connecting Rod Bearing for babbit bearings. This should be a part of your routine maintenance on your babbit engine,performed once every ten thousand miles to insure full bearing life.The following will demonstrate the measurement method using both plastigage and tinfoil techniques,as well as the 'feel' method of maintaining correct bearing oil clearance.Also included will be an oil pump inspection and repair,which should be performed along with the bearing adjustment.

[CM2]

First, a short discussion of babbit bearings,myths and truths.. Many engine builders today use precision insert bearings in model A engines, some use poured babbit bearings..Both methods are effective means of providing a bearing surface to cushion the crankshaft prior to oil flow,which essentially provides the 'bearing' for your crankshaft...a thin film of oil is all that exists between you and engine failure,and maintaining that clearance so the thin film of oil can do its job is critical to long engine life.The precision insert bearing is preset to your crankshaft journal ( journal is the name for the machined surface the bearing saddles) measurement and never needs adjustment,it snaps into place on the block and bearing cap. Babbit is a material made of tin,lead and antimony and is adhered to the block by pinning and the cap and rods by tinning with solder,it is then turned using a line bore to set the dimension needed for the oil clearance,minus a number of shims (.015 worth when new) to allow for adjustment.

Myth number 1: insert bearings are superior to babbit bearings...false,the model A splash and gravity oil system is not pressurized, which is what the insert bearing was designed for.It is harder and has less overlay babbit that the full babbit bearing, when it fails it usually results in a crankshaft failure as well.The babbit bearing,being a bit softer (more on that in a bit) when it fails generally does not cause a crankshaft failure.

Myth number 2 : Babbit bearings do not stand high compression....false,detonation from improper spark advance is one of the main causes of model A engine bearing failures,not compression. Babbit compression engines have ran sucessfully in diesel engines creating a 15 to 1 compression ratio. It is still the bearing of choice in large high load applications like ship propeller shafts

Myth number 3 : Babbit bearings come in one design only.....false,as will be shown below,Model A engines were assembled at the Rouge using a soft compound babbit,and many babbit men continued its use.The Model A engine should use US Grade 2 babbit,the babbit used for the Model T,..the T engine used a very light crankshaft that flexed under load,Ford compensated with harder babbit...you want it too,its also known as "high speed"babbit..more on this later.

[Kevin in NJ]

http://www.fordgarage.com/pages/babbittgrades.htm

[CM2]

Thanks Kevin ASTM grade 2 is also known as 'Model T babbit' and is suitable (hell recommended) for the A

[Kevin in NJ]

I specifically asked about Grade 2 years ago when I was researching babbitt, why everyone one was using it? Grade 2 is often used because it is easier to get. The correct Ford mix is tougher to find so everyone just goes with the grade 2. I am pulling this from memory so do not shoot me if I am wrong, the pour temp for 2 is lower (easier to pour) then for the correct Ford mix. The real Ford mix needs to be way up close to 1000 degree (again from memory and I may be off, but you get the idea) to pour and then it solidifies at a higher temp. It is harder to get the babbitt in the hole and forming the full shape and not need to break it out and do it again. Least that was our experience. The lead babbitt is easy to pour all day long. Of course it wont last long in real use.

[CM2]

Before you begin,you have to do the 5 P's...or as my old Chief Petty Officer used to say "Proper Planning Prevents Piss Poor Performance" first,order a complete engine gasket set,a rod and main bearing shim set and plastigage .001 to .003 green..from Brattons..get 5 quarts of your choice of engine oil too,your trusty creeper,drain pan,drop light,plenty of rags and clean that shop floor prior to work..here's an actual list of what you need for special stuff..

scotch brite extra fine body pad...these are great for evrything
Lubriplate no.105 engine assembly lube
permatex ultra grey sealant
brake clean
400 grit emory paper
green .001 to .003 plastigage
0 to 150 pound torque wrench
a quality set of vernier calipers or a 0 to 1 micrometer

PPE..you will be working on your back in a dirty environment doing precision work,wear safety glasses and coveralls..examination gloves if you roll that way.. but most of all

GET YOUR MIND RIGHT.you will be doing a very rewarding task on your car,something that will save you money and give you peace of mind when you drive..But it is repetitive patient time consuming work,take a break now and then,get it right not matter what,its never 'good enough' it has to be spot on.

[CM2]

OK,ready set...park the car in the shop and leave it over night without starting it...or two if you have the time,you will thank me later for this,trust me.Drain the oil and let that baby rest for atleast a day,then drain again..then get all your stuff laid out nicely and begin by jacking up the front of the car to a height where your comfortable working under it..'a bent arms length" set your jack stands wide on the front axle for room and take both front wheels off. Begin by pulling the rear main inspection cover(that half moon on the flywheel housing) then begin dropping the oil pan..remove one bolt on each side at the middle and stick a longer 5/16th NC bolt (about 2 ")and turn it in a few threads...then take out the rest of the pan bolts...the oil pump drops out with the pan the two long bolts allow you to 'control' the drop..yep,its heavy,yep,its awkward,be ready.Once that is done lay the oil pump on the bench and roll back under...this is what you'll see..and if you let the car sit for two days oil wont drip too much on your face..

[CM2]

Now get out from under the car,wipe off your face and hands and remove your carburetor and valve cover..some folks find it easier to drop the exhaust pipe,pull the fuel line and take off the manifolds and carburetor as one,its up to you.remove your distributor and drive shaft,remove the spring and shaft bearing (dead center of the picture) you have to do all this work to access the center man bearing nut..but no worries,you needed to do a valve adjustment anyway,and by pulling those manifolds you can finally fix that vacuum leak. Now's the time to check the shafts and shaft bearing for wear,eyeball the valve springs,and finally see how a model A oil system works...by gravity!!! those tubes allows oil to trickle down into the main bearings...that oil pump has the easiest job in the world.it lifts the oil from the pan about 8 inches...done...it floods the valve chamber and marks it sold..Okay,enough for tonight,my daughter is making mexican food...

[CM2]

At this point some decisions should be made..its a matter of draining the water and taking off the head to re ring the pistons or do a valve job..just saying...quick hone and ring,lap in the valves,change the timing gear and when your done with the rods and mains she'll be fresh as a daisy,perfect time for grade 8 head studs and a 6 to 1 head...but I digress The next move is to clean up your mess,and pull cotter pins..two behind the timing gear casting on the block,one between number two and three cylinder on the left side of the block,one dead center in the valve gallery you spent all that time exposing and two in the rear underneath,right by the flywheel.throw them away,and either buy new or do like I do and use modern chemical locking agents to hold the main bearing bolt nuts in place.Remove spark plugs,place transmission in neutral,these two things reduce drag on the crankshaft,further along you will be 'feeling' the drag on the crankshaft as you turn it...ambitious types who end up doing everything I listed above need to leave the cam gear off and the head off,they'll get the best 'feel'...but with the 'tin foil' method no matter the drag on the crankshaft we'll get the bearing clearance in that .0015/.0020 sweet spot we are looking for.

the bearing cap in the photo has soft babbit..one gentle swipe with the blade and it cuts..US Grade 2 Model T babbit requires quite a bit of effort to scratch it with the blade..remarkable difference.

[CM2]

Okay,once everything is cleaned up glasses and gloves on,we are ready to roll under and pull a main cap.Take a paint marker or other device ( a sharpie works too) and the brake clean and clean and mark all main caps and rod caps with their corresponding location,also place a mark denoting the cam side of the block THIS IS CRITICAL but if you mess up and don't do it we have ways of determining where the caps go,an old mechanics trick called 'witness marks'.CRITICAL:At this time,before taking the center main cap off its time to set a baseline "feel" for the amount of effort it takes to turn the crankshaft. grasp crankshaft throws ( the cast 'arm' that connects the journals see photo post #5) and turn the crankshaft..the amount of effort it takes to turn the crankshaft is your baseline feel...do it a few times,memorize this effort (not hard,its amazing how your brain can ascertain a torque value) give the crankshaft a little help with a bar to initiate the turn if necessary.but once its turning that is your baseline 'feel'.I like to pull the center first,it takes the most abuse and will generally give a good indication of what the rest of the bearings will look like.Put a 3/4 end wrench box end on the nut in the valve chamber center (the one you pulled the cotter pin out of) use a 5/8th's 12 point socket for the square head on the bolt.use an extension and a breaker bar (never use a torque wrench as a breaker bar)and remove the bolt and nut.repeat the process locking the nut with the 3/4 wrench located between 2 and 3 cylinders on the left outside of the block.CRITICAL: when removing the last bolt gently lower the cap and look for the brass shims (pictured in #4 second photo) make sure you keep all shims together and in the proper position.If there are no shims it means your babbit has been adjusted a few times before.We can make and adjustment on a bearing without shims but start saving your scheckles,I see a babbit man in your future.The first picture shows a center main bolt and the cap removed..the second shows a center main cap from an engine I have...see anything wrong?Now's a good time to mark the main cap bolts too,on the square end top to show the alignment for the cotter pin during reassembly.CRITICAL.the last thing you want to do is get the pan all back on and find out you cant get the cotter pins in.

[CM2]

A note about babbit failures.In the picture above the babbit failed.The block must be drilled and the babbit pinned to the saddle to lock the babbit to the block.,The cap and rods can be tinned with solder and the babbit is adhered to the solder.checking adherence to the cap is easy,you 'ring' it with a wrench,if it rings its good.The above failure was a shame,a nice engine that was freshly rebuilt,but the babbit didn't adhere to the solder on the cap.notice the crankshaft lived for another day.In failures with insert bearings this isn't always the case.The insert babbit lining is very hard and has poor embedment qualities,when it fails it most of the time it takes out the crankshaft too.

[CM2]

Time to clean and dress the cap and shims you pulled.spray the babbit with brake clean and polish with the BACK cloth side of the 400 cloth,use the grit side to clean the shoulders of the cap and block area.Pay careful attention to any babbit cracks.

[CM2]

Bearings everywhere,working at a mill today,walked by a whole pallet of micarta bearing shells

[CM2]

Okay.its time to set your reference,basically you need to measure where your at now to get a baseline for adjustment.

1st method :Plastigage...if you choose to use the plastigage method,first place a hydraulic jack under the crankshaft center weight (clear of the work)and jack a slight load up on the crankshaft,this insures an accurate reading.Set the plastigage on the cap (see picture)on the cleaned and prep'ed bearing cap you have as shown. (that's a rear main cap,a dirty one at that..take your time and clean yours spotlessly...extra credit if you see whats wrong with this one) Place original shim stacks you removed from the bearing you are measuring,make sure they are clean and set them in place.Install cap in position on the clean block/crankshaft,install the two clean bolts and tighten snugly (no need to torque yet,just nice and tight) DO NOT TURN THE CRANKSHAFT remove the cap,the plastigage will be spread out,use the packing sleeve gauge (picture 2) to measure.if it measures .0015 to .002 its good,if it measures .003 and above we'll have to adjust..using the razor blade carefully peel one shim off each shim stack,use the calipers to verify you remove a .001 shim,retest and repeat if necessary till the clearance (plastigage measurement) is at .0015 to .002.MAKE SURE YOU CLEAN THE PLASTGAGE OFF EACH TIME. Now once you reach .0015 to .002,apply a liberal amount of the lubriplate assembly lube on the cap,assemble the bolts and torque to 80 pounds...remember the 'feel' test I talked about earlier? do it now..dont be surprised if the crankshaft is bound and wont turn,Plastgage is precise,but doesnt take into account the deviations to bearing that has ran over time,it basically only read what it sees.if you encounter a tight crankshaft add.001 shim back on each side and check your feel again. A slight drag increase from your 'reference feel' is what you are looking for.Repeat this process for each main bearing cap and rod cap.The rod cap 'feel' is made easy by an old trick..tap the rod lightly and see if it side plays snugly..then do your feel test,if it doesn't side play its too tight,regardess of 'feel'.

[CM2]

2nd method: Tinfoil. ad measured .002 piece of heavy duty foil is placed into the cap as shown and installed as above with the original shims but no hydraulic jack,everything clean . attempt to turn crankshaft,if it moves,DONT SPIN IT,just moves an inch freely...then remove a .001 shim from each side and test again (see picture foe reference of .001 shim) test till it just binds the crankshaft..then remove the foil,you are a .0015 to .002...apply a liberal amount of lubriplate and check your feel..you should be spot on,the difference is the foil reads a wider area and takes into account deviations from wear,this is the method I use with good results,its easier and less steps than plastigage..but once again,its up to you. Regardless of which method you use,BE SURE YOU GET YOUR FEEL!!!.if you err,err to the slightly loose side,by the time you do a few a few bearings youll be a master,its not hard..and you'll know the Ford way..

[CM2]

3rd method: For the guys with no shims on disassembly..I pray for you,and your wallet..but this can be done,choose an above method ascertain a base line...but you don't have shims right? what do you do? wrap a piece of 400 emery paper around a constant..a piece of glass works best,but you can use anything that's dead nuts flat..and draw the cap evenly,sanding both sides at once,occasionally checking fit...if you think they guys with shims have it bad ,your wrong,your in for a slow,steady process of taking off the required measurement from the cap.But rest assured,you wont have to do it again for a long time,and the next time it goes to the babbit man,who gives back a fresh start..sanding the caps wont harm them for rebabbiting either.

[tbirdtbird]

CM2, this has been a super write up, and it almost takes longer to type it up than to do it!
You mention lubriplate but you have stressed that it is their assembly lube product, which is an important distinction from their white lithium grease product. Possibly any brand assembly lube would be ok.
I often like to add a dab of oil on the crank where the plastigauge is gonna contact, it seems easier to get the plastic off later. Comment?
I also use lacquer thinner to get the plastic off the caps, comment?
I have also had cases where I had to remove an unequal number of shims to get to the desired .0015-.002 clearance. Eg, ending up with 3 shims on one side and 4 on the other. At first years ago this bothered me, but I checked with my old-timer network who did all this for a living and grew up with these cars and they all said it was OK to do that. Comment?
Thanks for the write-up!

For the guys with no shims, Bill Barlow from Oregon used to re-babbitt your caps if you wanted. After all, the babbitt hardly wears on the block side when it comes to the mains.
Unfortunately , he has stopped doing this.
It would be a super service if we could locate anyone else doing this or get a babbitt shop, like maybe Herm, to start doing it. You had to specify your crank journal size of course

[CM2]

Proper fitting of the rear main cap is important,Ford does not use a rear main seal,well he does,the proper name of what was used is a 'labyrinth seal',the oil has to go through a mechanical maze to leak,in theory,in practice there are tricks to better your odds of having a dripper.One iws making sure it has a 3/8th drain tube,and its clear..another is to use the method the guys without shims use and dress the cap dead nuts flat.Spend the extra time polishing the cap and block where the cap seats,use a pencil line of permatex sealant on the outside edge of the cap before final torque,place a dab on the edges of the labyrinth and the main bolt heads.Seal the main bolts where they come out the block as well. I use hard washers and grade 8 nuts with sealant and loctite instead of the castellated locking system FORD used. BE SURE TO LINE YOU MAIN BOLTS UP FOR THE COTTER PINS BY USING THE MARKS YOU MADE. install the cotter pins before putting the oil pan on.Turn main bolt clockwise to re-position the cotter pin hole,never counter clockwise.

[CM2]

Oil pump service...at the same time,disassemble the pump CLEAN THE SCREEN and check the shaft fit in the bushings any play in the shaft hurts the efficiency. If the bottom plate has light gear marks you can use the dressing method to fix it..Major scoring? flip the plate,after you dress it first....Oil Pan and tray...pop the tray out with a prybar in the oil pump hole and clean it thoroughly...use the oil pan gasket method described in this forum,that cat is spot on.adjust your valves,check your intake/exhaust manifold alignment if you took it off..if you did the full freshen up good for you...if you just did the bearings good for you,now you have peace of mind ...

[CM2]

Well that about does it,everybody has an opinion or a different method feel free to post up add to the reference.One thing that doesnt change..WORK CLEAN,WORK SAFE,WORK HAPPY...pissed off?walk away..tired? walk away..if you cant eat off it don't assemble it.wear those safety glasses,oil burnt oil stings..

[CM2]

Assembly lube is critical in my opinion,a lot of engine wear occurs in two instances,a lack of lubrication on initial startup and a failure to get the assembly debris out of the engine after repairs..thanks for bringing that up...CHANGE YOUR OIL within a few hours of operation after setting your bearings.

I dont like plastigage.Its a quality product and an accurate, useful tool but it doesn't read enough of the full bearing,leading to more work than it should.Using the tinfoil method shortens the process.

I've seen unequal shims and have nothing against them, I lean toward loose rather than tight (in the tenthousandths range). if a mismatched stack puts you spot on great,but if it feels even a bit tight then no,rather be shade to loose than tight.The properties of today's oils,especially diesel grades provide the shear and load bearing characteristics Ford Engineers in '27 could only dream about.

Got a real good babbit man in Auburn CA,he has a nice touch and a feel for it,he's scary with a rosebud,he can sense when the temp is right..but he checks with a temp gun. Feed on his line bore is so slow you can comb your hair in the reflection off the bearing.He relatively young too,still holds a regular job..

[tbirdtbird]

I'm with you on Plastigauge. I use it if the motor is out and on a stand upside down. But if in the car, tin foil is way easier

[CM2]

The distinction between assembly lube and white lithium grease is important,feedback states any assembly lubricant can plug oil passages,especially in a gravity feed oil system.The assembly lube does have a very low pour point,its designed to wash out with engine oil...but there are votes against its use.

[WMWS]

Shimming Mains

Original thread

I am running 30* total advance and am careful about not lugging the engine with too much advance. I also never rev above 2000 RPM. So my question is how many miles do you all go before checking babbitt and adjusting shims if necessary.

[Tom Wesenberg]

If you keep it full of clean oil, I'd think it would be good to check them after 10K miles, then depending on what you find, thereafter maybe extend it to 20K miles. The quality of the babbit and who did the babbit job will be the deciding factor.

[Mitch]

Here is a tech thread on shimming

https://www.vintagefordforum.com/forum/model-a/technical-reference/52374-adjusting-babbit-crankshaft-main-and-rod-bearings

[WMWS]

Thanks good information Mitch. And congratulations on your 500 points in Branson.

[H. L. Chauvin]

"So my question is how many miles do you all go before checking Babbitt and adjusting shims if necessary."

FWIW: From experience:

A. About 99.99% of how many miles do you go will depend on the type of Babbitt provided, the care and accuracy attended to by who did the grinding of the crankshaft, who did the line boring, who did the Babbitt oil grooves and scraping, etc. etc.; how far advanced was the spark when driving, and last but not least, how often was today's better performing modern detergent oil changed.

B. After adjusting my Babbitted connecting rods and mains by the vintage "Feel Way" I was taught by vintage mechanics, I drove my 1930 coupe from 1959 until 1975 for 16 years with no knocking and no shim adjustments on mains or rods. Still have this engine in great shape.

C. I set my 1930 Town Sedan bearings, (on my engine with a HC Police Head), this same vintage feel way (12) years ago and I have no intentions of readjustments in many years to come.

D. Ford described setting Babbitt bearings by the "Feel Method" in his Model T Service manual, (still available), and I guess he did not think he had to repeat same in his Model A manuals.

E. The vintage mechanics I knew setting bearings in the 1940's & 1950's knew absolutely nothing about using aluminum foil, feeler gauge materials, and nothing about the 1950's later introduced "Plastigage".

F. All Babbitt bearings on all of our local large steam engines and internal combustion engines were only adjusted by the local "Feel Method".

G. Nobody ever thinks of this, but before X-Ray, we also had local vintage physicians who were talented enough to re-set broken arm and leg bones to where, by the "Feel Method", arms and legs could be used again ....... but, not everybody learned to be a good bone setter or not all learned to become a real good "Feeler".

H. Vintage Model A engines were successfully done as follows:

1. With engine turned upside down and engine disassembled, pistons removed from rods, timing gear removed, flywheel & timing cover removed, first remove all excess all oil from all Babbitt and all metal journals.

2. Begin with main bearings, one at a time, with equal amounts of shims, (more shims than that needed), on both sides.

3. On center main, remove equal amount of shims on both sides until absolutely "no" up & down movement can be felt; however, this center main bearing should have enough play so the crank can ever so slightly move side to side with "little" hand force.

4. After center main is correct, loosen bearing bolts so crank can turn very freely; however, leave shims in place.

5. Repeat step #3 & #4 for front main bearing and rear main bearing, not necessarily in that order.

6. After all (3) mains are set, oil all (3), tighten same slightly, but not yet torqued and go next to rods, one at a time beginning with more shims than that necessary.

7. After all rods are set, oil same. With all bearings tightened, engine should turn by hand with no excessive force.

8. Lastly, install oiled pistons, wrist pins, and rings.

Hope this helps to carry on a much used normal vintage tradition.

[BILL WILLIAMSON]

If it runs SMOOTH/QUIET, LEAVE IT ALONE!!!!!!
KDad & KDog

[Patrick]

The engine is mine was last rebuilt by a good local shop in 1961. I could not get the crank to make any noise no matter what I did running it, but, I could tell/feel a main was a bit loose. About 5 years ago I tightened the crank up [ .0015"] on all 7 and am not planing to have to do it again in my lifetime.

So to go along with what some have said, it depends on the quality of material and rebuild. It doesn't hurt [ well, at my age it does hurt] to check them just see where they are and look like. That may give some insight as to how long it may be until the next time.

[BILL WILLIAMSON]

DON'T FORGET to take your WATCH apart, every 1,000 Hours, for cleaning & inspection & marvel at its' construction---CURIOSITY kills LOTS of CATS!!!
Dad Dogguy

[Patrick]

DON'T FORGET to take your WATCH apart, every 1,000 Hours, for cleaning & inspection & marvel at its' construction---CURIOSITY kills LOTS of CATS!!!
Dad Dogguy

hehehehe, you don't clean your watch ? No wonder your late !

[BILL WILLIAMSON]

I STOPPED one of my New England, weight driven clocks, at the time Pat left me. Stopped the other one, at the time Gregg checked out.
Dad----GOD, I miss them.

[Patrick]

I STOPPED one of my New England, weight driven clocks, at the time Pat left me. Stopped the other one, at the time Gregg checked out.
Dad----GOD, I miss them.

I can fully understand, nice gesture.

[H. L. Chauvin]

Also FWIW:

When adjusting Model A Babbitt bearings, of importance is to realize that the Model A engine:

A. Uses a slow, splash oil flow lubricating system, and a slow gravity fed oil flow system with non-pressurized oil at Babbitt bearings..

B. In laymen's terms, Model A oil flow can be thought of as similar to the different types of water flow at a residential lavatory.

C. Water coming out of the lavatory faucet is forced with a fixed PSI pressure, and is similar to forced oil flow to bearings in a modern engine.

D. In a Model A engine, oil flow is slow and is similar to the slow gravity flow in a lavatory drain.

E. Oil is also a coolant circulating through bearings.

F. If one hears a Model A engine re-builder say he likes a tight engine with tight bearings, just proceed to step two.

[Chuck Sea/Tac]

Not that I like a tight engine, but ford did. He burnished them with an electric motor until the amp draw signified correct clearance.of corse this was mass production

[Kohnke Rebabbitting]

There are some things stated in these posts that are a little off the truth department, as I know them to be.

Thanks,

Herm.

[Mike V. Florida]

Even I saw a thing or two that goes against what I have read, but who am I?

[Mitch]

There are some things stated in these posts that are a little off the truth department, as I know them to be.

Thanks,

Herm.

Herm you are encouraged to offer your input. Alternative methods and views are welcome

[JB-OB]

With the engine in the car, drive train connected, which is the best method for checking the rear main?

In a perfect world, it would be helpful to take the weight of the flywheel off the rear main for measuring.

Thanks, JB

[Rumbler]

Thanks for this great summary. You mention positioning the main bearing bolts for installation of the cotter pins. What position should the cotter pin be in...does anyone have a picture of a correctly oriented cotter pin for a main bearing nut?