MTFCA Forum

I recently started working on the engine of my model s. The main bearings have to much play. In the manual i did see the babbitt bearing is a loose bearings is that the case? Can i just press a another bearing in de block?

The front and rear crankshaft bearings, N-404 and N-405, were solid babbit castings that were machined all over before being pressed into the front crankcase cover and rear of the crankcase.
The drawings for both of these bearings can be ordered from the Benson Ford Research Center at The Henry Ford in Dearborn, Michigan. The center main crankshaft bearing was made by casting babbit bearings in the top and bottom halves of the center main. The recommended practice is to have the crankshaft re-ground to a standard under size, then machining the inside diameter of the front and center bearings slightly undersize before pressing them into the crankcase. Then the front, center and rear main bearings be line bored by the engine rebuilder to insure the three bearings are in perfect alignment with one another.

There is a fourth Babbitt bearing that needs to be in alignment with the three crankshaft bearings. That is the rear transmission frame bearing, N-644.

The factory drawing for the rear transmission frame babbit bearing is also available from the Benson Ford Research Center.

Respectfully Submitted,

Trent Boggess

Hello trent,

Thanks for the quick reply! This really helps. Do you know if these bearings are available somewhere? Otherwise i need to make them.

Best regards Gerard

Closely inspect the flat mounting surface of your crankcase, where the cylinders attach. Many crankcases have "sagged out" in the center, causing the cylinder castings to lean in towards each other. Even if you line bore the main bearings, which will compensate for a sagged crankcase, your cylinder bores will no longer be perfectly perpendicular to the main bearing centerline. If this is the case, you may need to take a skim cut on the crankcase to true up the mounting surface. (You may also see the effects of a sagged crankcase on camshaft bearing alignment.)

My main bearings and rod bearings were still in great shape, but my rear main needed replacement. I made a mold out of wood and cast a new babbit bushing, which I then finish machined.

I checked the crankcase and it is indeed a bit sagged out thanks for the advise. Nice challenge to get it running again.

Another question from my side how much play should I create in length direction for the crankshaft? The flanges of the first and third main bearing should keep the crankshaft in place in length direction. But this is quite a distance and I may consider expension of the crankshaft caused by temperature etc.

Gerard_tt_ford wrote: ↑

Fri Jan 09, 2026 11:02 am

Another question from my side how much play should I create in length direction for the crankshaft? The flanges of the first and third main bearing should keep the crankshaft in place in length direction. But this is quite a distance and I may consider expension of the crankshaft caused by temperature etc.

Consider also, the expansion/growth of the aluminum crankcase. It will likely grow more than the steel crank. I would guess that .005"/.008" would be okay. I honestly can't remember what I set mine at.

Gerard - I pulled the print for the 4th rear main last year so the museum digitized it and made it public.

https://www.thehenryford.org/collection ... =gs-637640

By the way, all the digitized prints I can find on the Benson Ford website are cataloged in the members section of the EFR website - helpful resource.

Todd