Crank and rod bearing fitting question

D

Don/WI

Senior Member
I have a Diamond "A" block that I am checking out for a rebuild for my '30 Town Sedan. I checked the mains and found that after I had removed all the shims and using plastigage, I still have 0.002" clearance. The babbit looks to be like new. Is it possible to machine the caps to get the 0.001" clearance I need and if so, what is the proceedure to use? Or am I going to need a new babbit job?

I have the same problem with the rod bearings. Again, the babbit appears to be in great condition. There were no shims and using plastigage, I have 0.003" clearance. Is there a fix for this?

Thanks for any constructive feedback. Don/WI
 
Don - I wish I could answer that machining the caps would be acceptable, but someone with more knowledge than I will have to answer.

There is one thing I wonder about; could the crank have been turned and is slightly under size?

For what it is worth; I have never been able to successfully use plastigage. I use the aluminum foil interferance method. Do you think you might be getting a false reading from the plastigage?
 
Check the crank journals for any out of round condition. Caps were filed to take up clearance in the old days but that was a back yard fix and new caps were easy to get if the farmer decided to actually rebuild the ol fliver. .002 is ok if you want to drive it for awhile it is not excessive.
 
Don't be too hasty to trust plastigauge.
Assuming you're using the green .001 -.003 do this...
Find a 1" micrometer, carefully zero it, then lay the plastigage across the anvil and tighten it down to .001
Measure the flattened product now with the paper gauge and don't be surprised if it reads as much as .0025
I learned this the hard way when fitting inserts bearings.
My final conclusion is the stuff must harden with age and doesn't squish out properly.
Good fresh plastigage should be very soft...I think it's wax. Even though you might have bought it an hour ago...there's no telling how long it sat on the shelf.
I'd suggest take your micrometer to the store and buy what measures up.
 
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A flat plate --piece of plate glass, the table of a drill press, sandpaper (I like 80 grit 3M wet or dry) with oil ---a file will be faster --faster to do damage, a good way to cause a rear main leak, the sandpaper on a plate will show you a bad file job, and fix it.

Sometimes old babbitt can look good, but have a crust of oxide and debris imbedded in it that can cause fast crankshaft wear.
 
Craig Lewis said:
Don't be too hasty to trust plastigauge.
Assuming you're using the green .001 -.003 do this...
Find a 1" micrometer, carefully zero it, then lay the plastigage across the anvil and tighten it down to .001
Measure the flattened product now with the paper gauge and don't be surprised if it reads as much as .0025
I learned this the hard way when fitting inserts bearings.
My final conclusion is the stuff must harden with age and doesn't squish out properly.
Good fresh plastigage should be very soft...I think it's wax. Even though you might have bought it an hour ago...there's no telling how long it sat on the shelf.
I'd suggest take your micrometer to the store and buy what measures up.
Click to expand...


Craig, if you tested your plastigauge with your Mic. just the way you said, it will NEVER work for you. You have to coat the bearing, and the shaft, or your Mic. , with OIL. where the plastigauge goes, as the plastigauge will not flatten out with out lubrication, it Can't. When Plastigauge gets old, it still works accurately, but it is harder to handle, as it gets brittle,The Plastigauge Company does not stamp there packs, as such, to say to use oil, just as a tire is not stamped, that you have to use air, to inflate, they assume, a mechanic knows that. The last thing, on a bearing, never gauge the babbitt in the cap, the most accurate place is the steel shaft, as it has to spread out. Clean plastigauge up with lacquer thinner. Thanks Herm.
 
Herm - Thank you for that tip on Plastigage. I have never heard of that information. As I stated above, I have never had good success with Plastigage, and your tip of using oil may very well have been the reason.

That being said, I recently read on Fordbarn when using the interference method; to use only a piece of aluminum foil the length of the cap (front to back as oriented in the engine), and 1/2" wide (left to right or side to side as oriented in the car). When I first read the instructions for using the interference method; I thought the foil size was the same as the cap itself.

Have you ever used this method, and if so what is your experience?
Thanks,
 
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I was told by a trusted source that since the plastigage is oil soluble, you do want to degrease the journal and babbit to get the best reading. It also stays in place better away from the grooves un-oiled.
 
I think if you are having trouble with plastigauge you are doing something wrong. Think about what it is, its manufactured precision, and the physics of its use. I have never had trouble using it nor reading the results.
 
Bruce of MN said:
I was told by a trusted source that since the plastigage is oil soluble, you do want to degrease the journal and babbit to get the best reading. It also stays in place better away from the grooves un-oiled.
Click to expand...


Yes, Bruce, you should clean it all first, shaft, and cap, to make sure you get all the old oil, and any dirt out. Now, if you don't reoil, the plastigauge will dig into the babbitt, instead of spreading out, I don't know if it is oil, soluble, if it were, you would think you could clean it off with oil, and I have always had to use lacquer thinner, but always read the shaft, not the babbitt, or cap. The next time you check a bearing, try it both ways, then it won't take long to see what I mean. Thanks Herm.

Ps. Ron I'am pouring babbitt, hope to have time latter, Herm.
 
Ron/IA said:
Herm - Thank you for that tip on Plastigage. I have never heard of that information. As I stated above, I have never had good success with Plastigage, and your tip of using oil may very well have been the reason.

That being said, I recently read on Fordbarn when using the interference method; to use only a piece of aluminum foil the length of the cap (front to back as oriented in the engine), and 1/2" wide (left to right or side to side as oriented in the car). When I first read the instructions for using the interference method; I thought the foil size was the same as the cap itself.

Have you ever used this method, and if so what is your experience?
Thanks,
Click to expand...


No Ron, I have never used anything like that, we need a lot more accuracy then that, but I can tell you, it is not going to get it as close as Plastigauge, for that job. If your bearings are out of the car, then use a Post Mic., and an out side Mic., you can get them right to the 1/10 tenth of a thousands. The easiest way to adjust bearings under the car, if you don't like plastigauge, on mains, or Rods, is take out a shim .003, if that is what it is, on one side, torque to 80#'s and try turning the crank, if there is a heavy drag, or stuck, put in a .002 shim, if there is no drag, take out the .002, and put in a .001, if to tight, with slight drag, put the .002, back in, it will be the clearance you want. Now, back off the nuts on that cap, and just snug them again, and go on to the next cap. If you ever have drag on a shaft, that means that the bearing is pinching the shaft to tight, an it is not the shaft that is going to give. As my friend, Earl Davis in Minneapolis, Kennith Rebabbitting told me, that when he asked his Boss, at that time 1930, working at Clawson & Bals Company, about bearing clearance concerns, his Boss said, just remember, Their are alot of bearings running around out there, with to much clearance, but there in none running around with to little. Thanks Herm.
 
*Text below quote
V
Kohnke Rebabbitting said:
Craig, if you tested your plastigauge with your Mic. just the way you said, it will NEVER work for you. You have to coat the bearing, and the shaft, or your Mic. , with OIL. where the plastigauge goes, as the plastigauge will not flatten out with out lubrication, it Can't. When Plastigauge gets old, it still works accurately, but it is harder to handle, as it gets brittle,The Plastigauge Company does not stamp there packs, as such, to say to use oil, just as a tire is not stamped, that you have to use air, to inflate, they assume, a mechanic knows that. The last thing, on a bearing, never gauge the babbitt in the cap, the most accurate place is the steel shaft, as it has to spread out. Clean plastigauge up with lacquer thinner. Thanks Herm.
Click to expand...

*Mr Kohnke... I stand by my findings exactly as stated. Purchasing fresh soft plastigage did indeed give an accurate read on my 1" mike or I wouldn't print it here. As well, the fresh plastigage worked perfectly on my bearings ... while the old hard stuff had failed to flatten.
5 minutes of google searching has just turned up numerous warnings about the shelf life of plastigage.
...I invite you to look.
As well, I've posted here Clevite's (the manufacturers) full data sheet cautioning one to clean all oil from the shaft. The picture is small, so you'll have to transfer & enlarge it if you want to read the instructions.
*Also I've added a link.
I should add...it's doubtfull that instructions for something this critical would leave ANY steps to assumption as you imply.

Mr Kohnke I'm not bothered so much with your suggestion that I'm making this up as I go along....not as much as I'm alarmed by your missinformation being further missunderstood & leading to the potential failure of a student's engine.
I mean what if someone reads your posting & oils the ENTIRE bearing surface before placing the gauge down & ends up with far too much clearance?
Or shall we assume every student should know that?
I think if you purchase some fresh plastigage you'll indeed find it works dry as the manufacturer's data instructs...and you can stop adding oil to soften it.
While you're at it, check the FRESH plastigage with a good micrometer & I think you'll find it reads exact.
LINK to instructions http://www.3sx.com/store/faq/plastigage/index.asp
 

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I tried saving that Clevite pic, but it is too blurry when I enlarge it on the screen. Is it a scan or is it from the internet. If from the internet, could you post the link? If a scan, I'll PM you my e-mail address if you'll send me your scan file.

When I use the stuff it would stick to the journal. Maybe I didn't clean the babbit as carefully. I plan to toss my old Plastigage.
 
Herm - Thank you for the reply. Also, as usual with your replies concerning babbit, it makes sense what you stated; "Their are alot of bearings running around out there, with too much clearance, but there are none running around with too little".

You made mention of shims in size from .001" to .003". I have not been able to easily find shims made for Model A engines in .001" increments; I end up cutting out shims on my own. Do you have a source that sells shims ready-made for the Model A engine in .001" increments?

Thanks,
 
Bruce of MN said:
I tried saving that Clevite pic, but it is too blurry when I enlarge it on the screen. Is it a scan or is it from the internet. If from the internet, could you post the link? If a scan, I'll PM you my e-mail address if you'll send me your scan file.

When I use the stuff it would stick to the journal. Maybe I didn't clean the babbit as carefully. I plan to toss my old Plastigage.
Click to expand...
Good idea Bruce...I'll add this to my 2nd posting.
Link to plastigage instructions
http://www.3sx.com/store/faq/plastigage/index.asp
 
Ron/IA said:
Herm - Thank you for the reply. Also, as usual with your replies concerning babbit, it makes sense what you stated; "Their are alot of bearings running around out there, with too much clearance, but there are none running around with too little".

You made mention of shims in size from .001" to .003". I have not been able to easily find shims made for Model A engines in .001" increments; I end up cutting out shims on my own. Do you have a source that sells shims ready-made for the Model A engine in .001" increments?

Thanks,
Click to expand...

Ron, nobody makes shims in .001, and .002 thounands, years ago, the main bearing shims were in .002, now they use the .003, because it is cheaper. you have to buy the brass shim stock, McMaster Carr used to have it, M.S.C. , or a place like it. Lay your motor shim on top, and use a scalple to cut it out. Thanks Herm.
 
Some of you are doubting Herm? He is a professional and has taken the time to help this group. Believe and trust him! Plasti gauge has a good reputation for a reason!
 
I am sure Herm has used plastigage more times in a year than I will ever use in my life time. I have learned much from Herm's comments as well as others who replied in this thread. I now have information which I feel will give the success with plastigage that I did not have before.

I am checking the crank and connecting rod bearing clearances on my A this winter. Question - I do not have a heated shop, "Is there a temperature range plastigage must be used within?"
 
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