Amc V8 Crank Bearings

I pulled the crank shaft out of my parts 304 to put in my 360 to fix the spun bearing. The crank looks to be in really nice shape, but I want to put new bearings in while I have it apart. The bearings on the crank and connecting rods all have 10-72 stamped in them. Does that mean they are ten thousands over sized? The 304 was never taken apart as far as I could tell.

 

Get out your micrometer and see. If it was rebuilt or something, some places will put in different bearings to save money if only one journal was messed up...

 

The little tag on the right front valve cover might have some clues to what size brgs and piston bore is used at the factory. The TSM can decipher the code on it. If I recall there were some instances where the crank and cylinder bore were .010 under/over size new from the factory.

 

I measured the crank and it is standard size.

 

I believe the “10-72” is a date stamp on original bearing shells. I have some marked “11-73”. Standard size bearings usually do not have a size on the back side. Only oversized shells have a number stamped. Sometimes on OEM, and nearly always on aftermarket you will find “std” on standard sized shells.
On a particular original 360 I have, the original shells at marked .0005 and .0003, depending on the journal. I’m guessing these were used when a crank was slightly out of spec on the engine assembly line. My problem is these “oversized “ bearings are not available. Right now, I have one .001 and one standard shell on each journal. Plastigauge shows a good crush, but I have not run the engine yet. A micrometer and Plastigauge are your friends.
-Donny

 

Plastigauge is your friend. Don't guess while you have it this far down. Get the specs and check it with plastigauge. Napa or many other places stock what you need.