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Old 06-27-2022, 06:51 PM   #1
The "A" Team
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Default Do I need extra shims on main bearings?

Hi everyone. My cousin and I are working on the Model A Coupe my father left me after he passed away. The engine was supposedly rebuilt about 20 years ago, but then sat in a leaky garage unused and with no oil for that 20 years. When I got it, the engine was seized with rust in the oil pan and one of the main bearing covers rusted. After removing the bearing covers and cleaning everything up I got the engine moving again. However, today after we tightened the main bearings to 80 ft lbs of torque, the engine wouldn't move at all. There are shims under all the bearing covers, but do you think I need more or thicker shims to free up that engine at that torque?

Thanks in advance for the expert advice.

John
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Old 06-27-2022, 07:29 PM   #2
nkaminar
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Default Re: Do I need extra shims on main bearings?

Short answer is yes.

Please use an assembly lube when putting the engine back together on everything that moves. You can buy the assembly lube at any automotive parts store. Do not use lubriplate.

Use Plastigauge to measure the bearing clearance. It should be 0.0010 to 0.0015 inch. There are links below for Plastigauge and the shims. Adjust the shims one side at a time, alternating sides. It may be easier to start with a full shim stack and start reducing them rather than adding one at a time. The shims peel off the shim stack in layers. Measure and adjust all the bearings.

Make sure that there is no foreign material trapped in the bearing.

Are you using the Model A Ford Mechanics Handbook, Vol. I for reference?

https://www.snydersantiqueauto.com/p...8745&cat=41685
https://www.snydersantiqueauto.com/p...3982&cat=41685
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Last edited by nkaminar; 06-27-2022 at 07:44 PM.
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Old 06-27-2022, 07:57 PM   #3
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Default Re: Do I need extra shims on main bearings?

Is the engine in or out of the car? I've heard Plastigauge is not accurate with the engine in.
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Old 06-27-2022, 08:05 PM   #4
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Default Re: Do I need extra shims on main bearings?

Luckily, I actually have two copies of the handbook. I bought one, and then my friend bought me one for Christmas. When I put the bearing covers back on, I used Permatex 81950 Ultra Slick Engine Assembly Lube, because I heard it was good (hopefully I'm right). My cousin also recommended the plastigauge, and I placed an order for it right away.
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Old 06-27-2022, 08:06 PM   #5
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Default Re: Do I need extra shims on main bearings?

Yes, the engine is out of the car, on an engine stand.
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Old 06-27-2022, 08:28 PM   #6
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Default Re: Do I need extra shims on main bearings?

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I find it hard to believe that more shims would be required now than when it was originally rebuilt. I would go back thru the steps of checking each bearing clearance. Look carefully for rust, other debris. Are the connecting rods still connected? Please include pictures.
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Old 06-27-2022, 08:53 PM   #7
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Default Re: Do I need extra shims on main bearings?

Plastigauge is fine with the motor out and upside down. The weight of the crankshaft and flywheel won't be giving false readings, especially on the rear main.
As for more shims, I agree with Mr Rutter above but if nothing is found elsewhere, I'd loosen the main bearings one at a a time and check for tightness each time. That will enable you to identify which one is tight. Take it from there with plastigauge.
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Old 06-27-2022, 09:20 PM   #8
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Default Re: Do I need extra shims on main bearings?

We did that today (without the plastigauge) and it looks like the center bearing might be the culprit. We tightened the rear and front bearing, not to 80 ft lbs, and everything was ok until we tightened the center bearing. But again, without the proper torque, I'm not 100% sure.

Yes, the connecting rods are still connected.

I attached a couple of pictures.
Attached Images
File Type: jpg 20220618_143533.jpg (94.2 KB, 80 views)
File Type: jpg 20220627_152222.jpg (87.1 KB, 71 views)

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Old 06-28-2022, 06:11 AM   #9
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Default Re: Do I need extra shims on main bearings?

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Originally Posted by The "A" Team View Post
We did that today (without the plastigauge) and it looks like the center bearing might be the culprit. We tightened the rear and front bearing, not to 80 ft lbs, and everything was ok until we tightened the center bearing. But again, without the proper torque, I'm not 100% sure.

Yes, the connecting rods are still connected.

I attached a couple of pictures.
To begin with, please understand that the term “proper torque” is a modern term that really did not exist two plus decades ago. It is possible the rebuilder did not line bore it with 80 pounds of torque on the caps. It is also possible the rebuilder set the engine on the tight side for it to ‘burnish itself’ in during what is often called the ‘break-in period’. Also, what are you using for assembly lube? Could that be what is causing the engine to seize?

One other thing that you need to be certain of is that you did not install the center main cap on backwards or possibly install the shim pack onto the opposite side. You might try rotating the cap first to ensure this doesn’t correct your issue.

While this is probably not the most prudent way, I am going to suggest you consider tightening the caps as much as you can that still allows the engine to rotate, then either build a test stand or reinstall it back into the chassis, -then start the engine with cheap oil and allow it to run for 10-15 minutes. Allow it to cool and retorque the head gasket. Start the engine again and allow it to run again. Then drain the oil and remove the pan. Then inspect all three main caps for wear patterns which will tell you where the problem was. Then tighten each of the caps to your preferred torque and reinstall the pan. I suspect after the bearings have burnished, you will be ok.
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Old 06-28-2022, 06:13 AM   #10
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Default Re: Do I need extra shims on main bearings?

Check all the bearings for the proper clearance.

Brent has a good point that the cap may be on backwards or perhaps #1 and #2 got mixed. Usually there are marks on the caps to indicate where they go and which direction. The marks are usually on the cam side. There may be punch marks, one punch for #1, etc.
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Old 06-28-2022, 06:49 AM   #11
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Default Re: Do I need extra shims on main bearings?

The assembly lube I used was Permatex 81950 Ultra Slick Engine Assembly Lube. The main bearing caps do have little triangles on them, and both should point to the cam shaft? I think they both are, but I'll double-check. I'm 99% sure I didn't mix them up, as I put them in labeled bags when I removed them, but I'll double-check that too.
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Old 06-28-2022, 07:02 AM   #12
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Default Re: Do I need extra shims on main bearings?

Quote:
Originally Posted by The "A" Team View Post
The assembly lube I used was Permatex 81950 Ultra Slick Engine Assembly Lube. The main bearing caps do have little triangles on them, and both should point to the cam shaft? I think they both are, but I'll double-check. I'm 99% sure I didn't mix them up, as I put them in labeled bags when I removed them, but I'll double-check that too.
The '⛛' thingie does not always apply, so don't assume that is the proper orientation. It has been my experience over the years that not all engine rebuilders bother with installing caps with this orientation, ...and as a side note on that, I don't believe I have never seen Ford engineers specifying this on any of the drawings, so was it even proper protocol back in the day?
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Old 06-28-2022, 08:31 AM   #13
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Default Re: Do I need extra shims on main bearings?

When you get things sorted out, and if there are no marks on the bearings to indicate which one is which and which orientation, put marks on the cam side. Punch marks work or you can engrave numbers.
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Old 06-28-2022, 10:13 AM   #14
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Default Re: Do I need extra shims on main bearings?

When the main bearings were align bored, they may have set the clearance too tight. A lot depends on the person doing the work and their experience level. The process of prepping the block, pouring babbitt, peening the block mains, and performing the align bore sizing of the mains to the crankshaft is a complicated process. .001" to .0015 is good. A bearing can be tight at .001" clearance but may burnish in as long as it will turn. The crank should turn at .0015". I wouldn't exceed that figure. A person may have to get creative with shims. Some are better than others. Some are too thick. A person has to use care and good common sense to come up with the best overall clearance.

Do the main bearings already have shims? most folks that do this work use shims to give longer life to the bearings just like the OEM did. Adding more shims after the fact is not really a desirable thing but it can be done. Use oil on the plastigage to aid in flattening it out. New plastigage is the way to go. The stuff hardens with age and can cause indentation in soft bearing material.

Ford didn't use torque wrenches but it seems universally accepted that 70 to 80 ft/lbs of torque is acceptable. Some use more on the high compression engines.


PS. Pour a quart of oil down the distributor shaft bore then reset the distributor in place before starting the engine. This pre-oils the valve chamber and main bearing bearing feeds. The dipper tray will fill as fresh oil is poured into the crankcase. Assembly oil only works so long and it can take time for the oil pump to fill the chamber to proper fluid level after start.

Last edited by rotorwrench; 06-28-2022 at 10:22 AM.
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Old 06-28-2022, 10:41 AM   #15
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Default Re: Do I need extra shims on main bearings?

Quote:
Originally Posted by nkaminar View Post
Do not use lubriplate.
Ditto
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Old 06-28-2022, 08:20 PM   #16
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Default Re: Do I need extra shims on main bearings?

I had the same thought about the center main - that it might be on backwards. I can see AA and BB stamped in the block at the front and center main, but I can't spot any corresponding stamps on the main caps in the pictures.
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