Rear main adjustment

[glenn in camino]

Rear main adjustment
Working on my engine bearings. The rear main seamed too tight, so I put in 2 more 1 thousandth shins. Now it turns with a little drag but I think it might be too loose. I'm thinking about removing one of the shims, but then it will be uneven. What do you think?

[Patrick L.]

Uneven ? Thats done quite a bit. Shouldn't hurt anything.

What is the clearance ? I'd recommend checking with plastic-gauge. I set it to .0015"

[Synchro909]

Exactly as Patrick L says.

[Jim Brierley]

Adding .001 on each side should give you .001" more clearance. If being done with engine in car, put a jack under the crank to take the gravity load.

[1crosscut]

I agree. Get some plasti gauge so you know for sure. Just ask for the green plasti gauge at an auto supply store.

[Purdy Swoft]

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I set my rods and mains at two thousants clearance and use plasti gauge to measure the clearance . The hundred mph model A book reccomends three thousants clearance but I'm not racing .

[Arlyn Bieber]

My experience is plastic-gage will not give you an accurate measurement. Take a square of 0.001 shim stock, place it between the crankshaft journal and the bearing cap. Torque the bearing cap to 80ft-#, then try to turn the crankshaft by hand. If you can turn the crankshaft, remove shims until the crankshaft is locked and you can't turn it. At that point you should have 0.001" oil clearance.The shim stock is much more accurate than a piece of plastic-gage. Just my experience.

[Synchro909]

Originally Posted by Arlyn Bieber

My experience is plastic-gage will not give you an accurate measurement. Take a square of 0.001 shim stock, place it between the crankshaft journal and the bearing cap. Torque the bearing cap to 80ft-#, then try to turn the crankshaft by hand. If you can turn the crankshaft, remove shims until the crankshaft is locked and you can't turn it. At that point you should have 0.001" oil clearance.The shim stock is much more accurate than a piece of plastic-gage. Just my experience.

I've used pretty much he same process, only using a piece of newspaper soaked in oil. If the clearance is still too much after testing, you can get an idea of by how much by looking at how much the oil has been squeezed out of the paper. Experience helps but you'll work it out quite quickly. Newspaper won'y leave any marks on the bearing surface either.

[redmodelt]

I do the same thing with aluminum foil. Fold about a 1 inch square, ether 2 or 3 layers thick depending on the thickness of the foil. Gave up using plastic-gauge a long time ago. Never could get it to spread right. Model T and A babbitt, even the good stuff, has more "give" then newer type shell bearings.

[Delrayhuh]

Originally Posted by Arlyn Bieber

My experience is plastic-gage will not give you an accurate measurement. Take a square of 0.001 shim stock, place it between the crankshaft journal and the bearing cap. Torque the bearing cap to 80ft-#, then try to turn the crankshaft by hand. If you can turn the crankshaft, remove shims until the crankshaft is locked and you can't turn it. At that point you should have 0.001" oil clearance.The shim stock is much more accurate than a piece of plastic-gage. Just my experience.

Originally Posted by Synchro909

I've used pretty much he same process, only using a piece of newspaper soaked in oil. If the clearance is still too much after testing, you can get an idea of by how much by looking at how much the oil has been squeezed out of the paper. Experience helps but you'll work it out quite quickly. Newspaper won'y leave any marks on the bearing surface either.

Originally Posted by redmodelt

I do the same thing with aluminum foil. Fold about a 1 inch square, ether 2 or 3 layers thick depending on the thickness of the foil. Gave up using plastic-gauge a long time ago. Never could get it to spread right. Model T and A babbitt, even the good stuff, has more "give" then newer type shell bearings.

What these guys said.. I have had the same experiences

[Kohnke Rebabbitting]

Plastigage is easy to use and is always accurate.

The only thing that you have to do to make it work, is use it right.

Clean the shaft, and cap of the old oil.

You can NOT use it dry, as it will not spread out on a dry surface, and Babbitt is worse, as it is soft, it can sink in.

Do not put the Plastigage, across the whole width of the bearing, just a piece on each side.

Put a couple-three drops of clean oil on the shaft, and cap, and spread it in a straight line, across the bearing, and shaft.

Use a 3/8's, to 1/2 inch piece of Plastigage on both sides.

Tighten the cap to the Spec's it should be, and then remove the cap.

Then read the shaft, not the Babbitt or cap side.

You just can't use it dry, even on modern inserts. If it is used dry in a Babbitt bearing, it will imprint it's self, into the soft Babbitt, and leave a mark.

Oil also keeps the Plastigage in place, and straight, rather then the alternative of it going every direction then what you want.

When you are done, clean the used Plastigage off the shaft, and cap, using a little lacquer thinner, on a paper towel.

If Plastigage didn't work, it would have been gone 40 years ago.


Dave, look, ever seen these before!

Thanks,

Herm.

[Synchro909]

When I use Plasigauge, I do as Herm described. Either the paper or Plastigauge work fine for me. I don't get precious about advocating either.

[1crosscut]

Yep Herm those do indeed look familiar. Your advice is spot on.
Merry Christmas.

[George Miller]

Originally Posted by Kohnke Rebabbitting

Plastigage is easy to use and is always accurate.

The only thing that you have to do to make it work, is use it right.

Clean the shaft, and cap of the old oil.

You can NOT use it dry, as it will not spread out on a dry surface, and Babbitt is worse, as it is soft, it can sink in.

Do not put the Plastigage, across the whole width of the bearing, just a piece on each side.

Put a couple-three drops of clean oil on the shaft, and cap, and spread it in a straight line, across the bearing, and shaft.

Use a 3/8's, to 1/2 inch piece of Plastigage on both sides.

Tighten the cap to the Spec's it should be, and then remove the cap.

Then read the shaft, not the Babbitt or cap side.

You just can't use it dry, even on modern inserts. If it is used dry in a Babbitt bearing, it will imprint it's self, into the soft Babbitt, and leave a mark.

Oil also keeps the Plastigage in place, and straight, rather then the alternative of it going every direction then what you want.

When you are done, clean the used Plastigage off the shaft, and cap, using a little lacquer thinner, on a paper towel.

If Plastigage didn't work, it would have been gone 40 years ago.


Dave, look, ever seen these before!

Thanks,

Herm.

Herm nice looking bearings, I can see you know how to do it right.

[Kohnke Rebabbitting]

Originally Posted by George Miller

Herm nice looking bearings, I can see you know how to do it right.

Thanks Jim, for the complement, but these rods are not ours, as we don't do Model T, A, or B rods any more, just the mains, as there isn't any money in the rods. We do all other bearings, and get 65.00 an hour shop time.

The engine owner had gotten them some where.

You can always tell our bearings, as they have a much higher finish on them.

Thanks Jim,

Herm.

[hardtimes]

Originally Posted by Kohnke Rebabbitting

Plastigage is easy to use and is always accurate.

The only thing that you have to do to make it work, is use it right.

Clean the shaft, and cap of the old oil.

You can NOT use it dry, as it will not spread out on a dry surface, and Babbitt is worse, as it is soft, it can sink in.

Do not put the Plastigage, across the whole width of the bearing, just a piece on each side.

Put a couple-three drops of clean oil on the shaft, and cap, and spread it in a straight line, across the bearing, and shaft.

Use a 3/8's, to 1/2 inch piece of Plastigage on both sides.

Tighten the cap to the Spec's it should be, and then remove the cap.

Then read the shaft, not the Babbitt or cap side.

You just can't use it dry, even on modern inserts. If it is used dry in a Babbitt bearing, it will imprint it's self, into the soft Babbitt, and leave a mark.

Oil also keeps the Plastigage in place, and straight, rather then the alternative of it going every direction then what you want.

When you are done, clean the used Plastigage off the shaft, and cap, using a little lacquer thinner, on a paper towel.

If Plastigage didn't work, it would have been gone 40 years ago.


Dave, look, ever seen these before!

Thanks,

Herm.

Hey Herm,
Thanks, for the tutorial ! Refreshes my memory as to correct process and proper way to be done. Something that most don't do that often.