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Old 04-11-2018, 06:37 PM   #1
Nosetime
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Default Lesser of two evils..cracked main babbit or used replacement?

Gentleman, I need some experienced engine builder advice. Save the "rebuild it", I know what is best practice, but I need to get some miles out of this engine before a complete rebuild. I posted my question a while back and some of the best here agreed to just run it, without to high of expectations. But, this weekend I bought 3 rear mains with one that has good babbitt...for $5. It looks like shelf wear scratches and very solid. I did not clean it up so the pics are as found. It appears to fit the crank very well, so my question. Would you try and use this instead of the cracked one? My thought is to assemble with prussian blue or something, Give it a few turns..carefully fit, then spec carefully on assembly. I assume this has been done before?
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Old 04-11-2018, 06:45 PM   #2
Kurt in NJ
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Default Re: Lesser of two evils..cracked main babbit or used replacement?

Ford sold pre finished caps, fit it and put it together
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Old 04-11-2018, 06:49 PM   #3
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Default Re: Lesser of two evils..cracked main babbit or used replacement?

Kurt, any advice on the fitment? BTW, I noticed the picture makes it look worse than it is. I will be thrilled if it works, as the rest of my engine is looking pretty good. Thanks, Greg
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Old 04-11-2018, 07:48 PM   #4
Bill Pursel
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Default Re: Lesser of two evils..cracked main babbit or used replacement?

you need to keep in mind that the crank main could be std. .010,.020,.030 or more so replacment main cap needs to be the same.
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Old 04-11-2018, 07:57 PM   #5
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Default Re: Lesser of two evils..cracked main babbit or used replacement?

Yes, Bill I thought the same thing. But, would the proper original that is broken, be better than a "close enough" replacement? Again, my expectations would be realistic either way. Would there be a way to spec out what I have to help the decision? I'm runnin' one or the other either way.
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Old 04-11-2018, 08:06 PM   #6
Tom Wesenberg
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Default Re: Lesser of two evils..cracked main babbit or used replacement?

I'd also fit it and run it. Shim to get .0015" clearance. If the diameter is correct, then you shouldn't be able to move the main left and right against the block more than .0015". If you can move it 10 or 20 thousandths, then you need to find a better fitting main cap.
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Old 04-11-2018, 08:19 PM   #7
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Default Re: Lesser of two evils..cracked main babbit or used replacement?

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Originally Posted by Bill Pursel View Post
you need to keep in mind that the crank main could be std. .010,.020,.030 or more so replacment main cap needs to be the same.
Those are the standard sizes for undersized inserts. For babbit, they can be anything. One of the things I like about babbit is that a reconditioner can grind the shaft just enough to clean it up, then bore the babbit to suit. Only the bare minimum is removed from the journals. If the cap the OP has is an originall Ford replacement, what you say may be correct but otherwise, there is a good chance it is not.
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Old 04-11-2018, 08:32 PM   #8
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Default Re: Lesser of two evils..cracked main babbit or used replacement?

Greg, you did not mention if you have shims on that main, but why not install a few shims and then a small piece of plastigage, tighten down the cap and then remove it and check for clearance and repeat with less or more shims if needed. Would not take long. That looks like a nice cap. Just my 2 1/2 cents.
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Old 04-11-2018, 09:09 PM   #9
Ernie Vitucci
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Default Re: Lesser of two evils..cracked main babbit or used replacement?

I agree with ZZ...Ernie
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Old 04-11-2018, 09:36 PM   #10
Kevin in NJ
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Default Re: Lesser of two evils..cracked main babbit or used replacement?

By fitting, put the crank in and spin. High spots should be shiny chect fit. Bit of an art to know what to do next, but if the crank turns tight and the clearance if good then you need to bring down high spots. I am not very experienced at it so I do not dare go further. Obviously you will playing with shims at the same time to get the fit.

FWIW there are special babbitt scraping tools. You may have to make due with a knife edge.
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Old 04-11-2018, 10:09 PM   #11
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Default Re: Lesser of two evils..cracked main babbit or used replacement?

I dont care for plastigage,especially if your fitting a cap like this..the reading the plastigage gives is too narrow for fitting. Id use aluminum foil,Ford used a red lead compound to read the entire face of the bearings,not just the 1/8" the plastgage reads. Its important to figure out what kind of babbit the caps you are considering to use have.Model T US grade 2 babbit is hard and will take a sharp knife to shape,stock model a babbit is way softer,and easier to shape.

Aluminum foil ,heavy duty folded is about .002,use a mic to set. Cut foil for full width of the bearing shell,install the shell and torque it.remove shell and 'read' the foil.Make a bearing knife and scrape the bearing to fit. Impression fluid like Ford used is good as well,it will tell you where you need to concentrate with the knife..patience is key,cut,fit and check,repeat till you hit the sweet spot.002 to .0025. Grade 2 babbit is harder to dress with a knife,A babbit cuts easy.Take you time,hand fitting babbit takes time and patience,its the method Ford mechanics used.

Its important to do all work using .030 shims,that way when its fitted you get full life out of the bearing..but dont worry if you remove a shim or two to make up for overzealous knife work,it happens.Babbit wears about .001 per ten thousand miles or so,so losing a shim or two fitting will still give good life.So many neglect to properly check and maintain their bearing clearances, with the engine in the car its hard dirty work..but necessary for full engine life.

Last edited by Railcarmover; 04-11-2018 at 10:16 PM.
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Old 04-12-2018, 06:57 AM   #12
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Default Re: Lesser of two evils..cracked main babbit or used replacement?

Thanks to all. The engine is completely disassembled on a stand. Kevon and Rails method is about what we had figured. Thanks for the nicely described instructions! ZZ, yes of course we will shim everything correctly. I am finally at the end of a year of parts collecting, cleaning, fixing and info gathering! We are doing the Tardel rear frame step this week and frame is ready to be blasted/painted and start putting it all back together! The engine is ready to be assembled. I am really happy to have found that main, the broken one would have bugged me everyday, now maybe I can drive it for some time before a complete rebuild.
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Old 04-12-2018, 06:58 AM   #13
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Default Re: Lesser of two evils..cracked main babbit or used replacement?

Railcarver. Any suggestion on making the babbitt knife? Thanks, Greg
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Old 04-12-2018, 07:47 AM   #14
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Default Re: Lesser of two evils..cracked main babbit or used replacement?

Hardest steel you can get your hands on..german kitchen knife,wood chisel..Ford mechanics made them out of old files. Sounds like the engine is out on a stand,nice,it makes the work easier.Test your replacement cap first,if its oversize it will be tight at the parting line(edges) so you'll most likely be working the edges first. Here's to hoping you roll a 7 on the comeout,that the cap you scored for 5 bucks fits on the first fit up.DONT FORGET THE SHIMS!!

Once you are done you can polish the babbit and take out micro abrasions with the BACK of a piece of emory cloth.

The biggest part of the job is you,get frustrated? back off,this is time consuming tedious work,I spend time on ergonomics..no hunched over squinting to see stuff..

If all else fails you can run that cracked one,polish it up good,fill the cracks on the thrust with epoxy..if the cracked chunk is still adhered to the cap..
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Old 04-12-2018, 08:21 AM   #15
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Default Re: Lesser of two evils..cracked main babbit or used replacement?

Scrapers show up on eBay fairly regularly.

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Old 04-12-2018, 08:34 AM   #16
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Default Re: Lesser of two evils..cracked main babbit or used replacement?

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Originally Posted by Railcarmover View Post
Model T US grade 2 babbit is hard and will take a sharp knife to shape,stock model a babbit is way softer,and easier to shape.
Not to get off topic but why would Ford have used much softer babbit in the Model A?
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Old 04-12-2018, 06:23 PM   #17
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Default Re: Lesser of two evils..cracked main babbit or used replacement?

Ok guys, for those curious. There are plenty of Babbit scrapers on ebay and some great videos on youtube. I am ready for this! Thanks again to railcarmover, I will use your suggestions.
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Old 04-12-2018, 06:53 PM   #18
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Default Re: Lesser of two evils..cracked main babbit or used replacement?

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Ok guys, for those curious. There are plenty of Babbit scrapers on ebay and some great videos on youtube. I am ready for this! Thanks again to railcarmover, I will use your suggestions.
And plenty of time. It's a slow, arduous process. Patience is a must, as has been said.
A little Prussian Blue on the shaft, test fit and turn. Dismantle and scrape away the transferred blue and repeat till you have a good contact.
Keep the coffee coming!
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Last edited by Synchro909; 04-14-2018 at 05:45 PM.
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Old 04-12-2018, 08:42 PM   #19
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Default Re: Lesser of two evils..cracked main babbit or used replacement?

I just did this. I used a bearing scrapper and I used a red sharpie as my marking. I used platigauge to get it to .0015. I broke the slinger seal groove on my original rear main and the one I found was for a .010 under crank mine is stock. It took 5 hours of scrapping you will get about 1/12 to 1/20th of a thousand per scrap and only in a very small area. But it works. I make a quick grid on the bearing with the marker. set the cap on and if its .010 under it will have gaps but as you get close the gaps will close then after some more it will free up under torque. then you have continue to get your clearance. A good vise that will hold your work at a comfortable level is a must for 5 hours of bearing scrapping.

If you can make it happen with shims try shims first.

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Old 04-12-2018, 08:45 PM   #20
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Default Re: Lesser of two evils..cracked main babbit or used replacement?

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Not to get off topic but why would Ford have used much softer babbit in the Model A?
Umm, Ford didn't use softer babbitt then grade 2.

The copper makes it harder and hotter to pour. The 2 stuff is just what is easy to get and works ok. You have to have a large batch made to the Ford spec if you want the original numbers. At least that is what we have found trying to source the correct babbitt for our own cars.

Babbitt grades
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