New Babbitt Mains - How Tight

U

ursus

Well-known member
How tight should a Model B crankshaft be in a newly rebabbitted engine block? After shooting 10/30 oil into the oil ports for each bearing - without camshaft, rods, or pistons installed - the crankshaft will only turn with a minimum of 25 lbs of torque. This seems pretty tight to me as I've never worked with newly babbitted mains before. What should be the appropriate level of torque to turn the crankshaft in this situation?
 
ursus said:
How tight should a Model B crankshaft be in a newly rebabbitted engine block? After shooting 10/30 oil into the oil ports for each bearing - without camshaft, rods, or pistons installed - the crankshaft will only turn with a minimum of 25 lbs of torque. This seems pretty tight to me as I've never worked with newly babbitted mains before. What should be the appropriate level of torque to turn the crankshaft in this situation?
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Depends on whose standards you are choosing to use. :o

If the bearing has been burnished, then it is too tight. If not, then the journal pin(s) is likely just touching the high-spots of the bearing and the assembler chose to set the clearances tight in order for it to "self-clearance" during the initial run-in. Not my preferred method however there are many successful rebuilders who choose this method due to budget/time constraints.
 
I usually put an extra .001" shim under one side of each bearing, this gives another .0005" clearance. I also do this on the rods.
 
Brent has the right advice. The bearings will get hot on the initial run and the babbett will expand to tighten up the clearance. The tight bearings will wear down the high spots. On cooling the clearance will loosen up again. This will repeat until the correct clearance is obtained. This is one advantage of poured bearings. The first run should be short, about 15 minutes, followed by longer runs. And not high speed or high load. Ford recommended 25 mph for breakin. I think it was 500 miles. Ford did an initial breakin of his engines using an electric motor to turn the engines.

Use the normal detergent multi grade oil for the breakin. Change the oil after 500 miles. The next change can be longer.
 
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ursus said:
How tight should a Model B crankshaft be in a newly rebabbitted engine block? After shooting 10/30 oil into the oil ports for each bearing - without camshaft, rods, or pistons installed - the crankshaft will only turn with a minimum of 25 lbs of torque. This seems pretty tight to me as I've never worked with newly babbitted mains before. What should be the appropriate level of torque to turn the crankshaft in this situation?
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Have you checked the clearance of the mains?
On a Model B clearance should be .002" on rods and mains
There will be a distinct pull to initially get the crank moving this is called "Stiction". Once you break the death grip the crank will spin freely it work was done properly.
 
Here's my exprience! Had my Engine rebuilt by Schwalms. beaultiful job! Started it up , ran it for a while, 20 minutes or so. The tank ran out of gas. wife called me for supper. Tomorrow is another day. I put more gas in it and started it again, ran it for about twenty ,minutes tp half an hour and I had to shut it down. (I don't recall why). Time for a oil change! I didn't get to it for a long while (Too long ?) When I tried to start it again the cranking got slower and slower until it didn't crank any more. It was seized good and proper! It was now well past the guarantee and I didn't want to go back to the rebuilder, begging! I really was stuck. I took the corners off a piece of4x4 and with a big hammer, I smote that sucker Good! Don't bother trying this , it didn't work! (Maybe the hammer wasn't big enough, ya think?) I curtailed the hammer cure, swallowed my pride, and made the call (I felt like General Lee surrendering to General Grant!). Ora Landis must have sensed my humiliation because he couldn't have been more gracious when I told him what's wrong. Yes, Pull it out and bring it over and we'll fix it! It didn't involve the rings and pistons, it was the mains! By some freak of metallurgy they will tighten up and sieze. When I described the problem, One guy, a rebuilder, said that he had experienced the problem too. His solution was to bore the mains .0005 oversize which sounds great to me. All I now know is the engine is not seized, Ora Landis is great! and the engine runs great! And Bob's your uncle! (Where'd That come from anyway?

Now there's one possible fly in the ointment! Suppose the 3 journals are not concentric! For whatever reason! I had model A engine that the crank and babbitt were ground and repoured. This engine was well done and was tight as heck, but never seized. When I brought it home, the crank could not be turned by hand,(no pistons) but it gave me no trouble.
Terry
 
When you work on the bearings, make sure to use some assembly lube when you put it back together. That will help with the initial startup.
 
Some good advice above.
As J and M said, it'll take just a bit to get it turning and then should spin freely.
If its still not assembled, I'd recommend checking the clearance. I like .0015".
 
A lot depends on what type of align boring machine the builder has and what shape the crank is in. The mains are generally sized to the crankshaft journals to be used. The clearance should be close but it has to have some clearance to allow oil to get in there. It should be good with .001" to .0015" With less than .001", it' going to be tight. As long as the caps are shimmed properly at the outset, follow on adjustments can be made if necessary.

Ford turned the engines with the big electric motors and monitored the current draw on the motors. They had it down to a science for their initial bedding in process. If it took to much current to turn then it went back to a separate line for repair consideration.

I'm not one for running newly overhauled engines with no way to pull a load on them. They won't break in well with no load. Some get lucky but I don't like to leave things to chance.
 
I think its best if you put it together on the loose side, then in a 1000 or so miles drop the pan and set the clearances to proper spec. I understand why builders don't want to do that as its more shop time and depends on the customer bringing the car back. If someone is capable of doing their own work then a little extra time spent could save you some serious headache later. Just my two cents. I've heard lots of horror stories about seizing from too tight of build, although a cold seize isn't nearly like a hot seize.
 
Now there's one possible fly in the ointment! Suppose the 3 journals are not concentric! For whatever reason! I had model A engine that the crank and babbitt were ground and repoured. This engine was well done and was tight as heck, but never seized. When I brought it home, the crank could not be turned by hand,(no pistons) but it gave me no trouble.
Terry
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I had the crank ground by one firm, and had another firm do the rebabbit using the crank as their "guide."

Work pretty much done he calls.

"Your bearings are done but we noticed a problem Houston. Your crank is not straight. Block fits the crank fine but when everything is bolted together the crank is seized. We traced it down to the crank is about 0.020 out of alignment (non-concentric between the three journals.)

The solution is to have the grinder "straighten" the crank. Large press, foot pedal, "bounce" the hydraulic piston on that crank about 2" out of concentric and hope it springs back straight.

It took a few heart rending minutes. But as he left it it was within 0.0005.

And then he checked it with magnaflux/dye check (forget.)

"Now when this crank heats up will this stay the same?"

"Dunno - bring it back if you find it is a problem."

Easier said than done.

Now many miles later I would say it did stay the same.

I would say in the future would be best to have someone with experience in Model A engines do the grinding - the crank is considerably more flexible than most modern crank grinder experience.

If you go there make sure the flywheel flange is "faced" and perpendicular to the rotational center.

Joe K
 
Regarding not wanting to go back to the original rebuilder: if I rebuilt it, no matter how far out of warranty it is, I would prefer you to bring it back. Under the circumstances you have outlined, I would be glad to stand behind it.
 
As the OP I appreciate all the great advice and commentary from the experts here.

I traced the tightness down to a bit of a kink in the center main where the journal had about 0.0013" run out and was able to correct that to a total of 0.0007" run out. It was still a bit snug at that point due to a high spot on the forward end of the bearing. This was reduced with a modest 10% mixture of extra fine Timersaver in 0-20 weight oil and things are now moving smoothly with the normal level of "sticktion" noted by J & M Machine.

All seems well with that part of the assembly although further progress will be delayed because of an injury to my right hand. Here's hoping it doesn't put an end to my Model A hobby. Cheers, all!
 
Ricky Mullen said:
Regarding not wanting to go back to the original rebuilder: if I rebuilt it, no matter how far out of warranty it is, I would prefer you to bring it back. Under the circumstances you have outlined, I would be glad to stand behind it.
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Good to know! It's just as though I felt I had done something wrong. I couldn't recall what it might be, but since I had worked on it last, it was my fault!, I didn't want to face that. Ora Landis couldn't have handled it better. He was a real gentleman about it. I haven't been around model A s enough to know all their idiosyncracies and that this sometimes happens. Exactly how, I can't even begin to explain. The engine was fine as I ran it in and then I went to start it again and it tightened up (Cranked slower and slower ). Nothing would move! Again, I hold Ora in my highest regard for his help with that problem.
Terry
 
So how long should babbit last before the rods need taken up just a bit? This assumes using the high-tin babbit, not the "diesel babbit".
 
Depends. Many factors are at play. How was the engine built. How was it broken in. How is it being driven. What was the quality of the Babbitt. What quality oil is being used. Sometimes the bearings need to be taken up in a short time, maybe 10,000 miles. Running with the ignition too advanced will considerably shorten the rod bearing life. If the rods are bent that will also considerably shorten the life. Rod bearings can go 50,000 miles or more before needing to be taken up. Listen for the rod bearing noise. They will tell you when it is time.
 
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Some interesting comments here. I am very glad that the o.p. is happy with how oris handled the situation. Always call the rebuilder, you will get the best help from him, particularly from oris, a proven quality shop. IF the crankshaft is ground properly it should have no runout anywhere. Less than .0002 that is two tenths of one thousands. IF the Babbitt is line bored with a precision line boring machine a clearance of .0015 is perfect. a or B. With crankshaft installed in block there may be some sticktion as mentioned but turning the crank with bare hands should be no problem. Having done hundreds of line bores you don't need to ask me how I know. An assembled shirt block can be turned over very easily with wrench and socket on the crank nut. This is true of any rebuilt engine, modern or antique. Anything other than that is crap. Step on the starter and it starts. Videos on you tube of towing an A to get it going is just a hack job.
 
Plastigauge is my friend. Also Scotch Brand magic tape - to give 0.0007 clearance. Applied to the shim and then cut out to the outline using an X-acto knife.


Its a LOT easier done with the motor out and upside down in a stand.


Joe K
 
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