Main Bearing Shims, a question ???

[dobro1956]

Its been awhile since I rebuilt a T engine. The current main bearing shims appeared to be made wrong to me. But when I looked in the original 1928 parts catalog, the shims are like the current repros. I remember the shims I used to use, had a small ear on the inside of the shim, that sat between the babbitt at the ends of the bearing. I thought those small ears were there to give a little support to the bearing and help keep it from "lifting" away from the block. The "ears" only go about 1/2 way of the babbitt, but it would be enough to help "trap" the bearing in place at the ends. Without the "ears" there is nothing to keep the bearing from moving away from the block. I know there are lugs cast into the bearing shell that fit holes in the block. But those stop the bearing from turning, but not "lifting". The "ears" also create a little oil trough that also may be of benefit. I know Ford used the style with no ears (on millions of cars) , but I really like the other style better. The current engine Im building has the old style shims in it that have the ears toward the center. That style shim may have been an aftermarket style shim. I am out of that style of shim, so does anyone know where to finds some. Or does anyone have some they will part with. Has anyone else noticed the difference, or did I just have a supply of aftermarket shims a long time ago...

[Kohnke Rebabbitting]

The bottom shim is for a Model A, and B Ford, Front, and center Mains.

[D.Yoder]

Great to see you back on the Forum Herm,

[Ken Buhler]

I agree with Dean, I'm glad you are back Herm.

[V4F]

Hi Donnie
Hopefully a couple pics are below.

[dobro1956]

I thought the front and center shims may have been Model A. I ordered a set of them off e-bay and should have them soon. "BUT" The model A set does not explain why I have (and had) a longer shim with inside "ears" for the Model T rear main. I did not get a picture of it for the pictures above, but I do have a long shim set with "inside ears" in my engine for the rear main. Ill get a picture of the rear shim today.

I may be just thinking crazy, but it appears to me a shim with "ears" on the inside that sit on the Babbitt at the ends of the bearings could only help. The Ford style shims and also the current repros do not give any support at all to the bearing. For example: Lets just say I have set of Ford style .004 shim packs on each side of the bearing. And lets say I am running .002 clearance on my bearing. Those measurements will "allow" the bearing the ability to break free of the block and "lift" .002. In effect allowing the bearing to slowly "beat itself to death". But the little "ears" sitting on the babbit bearing will keep the bearing from lifting. It may be the reason why Ford changed to the inside "ears" on the Model A. ??? I used to have a box of the shims with the "inside ear" where all three shims fit a model T. But I can not find them or I used them all up.

Im probably OK as to having enough shims for "this" engine, because I can use my old set. They are laminated so I can peel off a shim for my final adjustment.

But I really would like to find some more.

Thanks for the input

[Dan McEachern]

You can cut the A rear main shim and use it in a T engine as well. It will be a little shorter than a T rear main shim as the A rear main is 3" long from thrust to thrust, but that won't hurt anything.