Do OEM main bearings have date codes?
 

Just for fun and out of curiosity, is anyone here familiar with date codes on SBC Main Bearings (if there actually are date codes)?

I just pulled apart the 302 block from my (October ‘68) 69 Z/28 and while I think it has never been apart before, I was wondering if the codes on the Main Bearings would help determine if they are factory original parts??? They are all standard dimensions of course….

Here are the codes from the front main cap bearing halves:

Both bearings have these codes on them:
GMM400
Capitol A inside of a circle and 55084

Plus:
One bearing half has 171P8 and the other half has 269L8

Do these codes make sense to anyone???

Thank, Charlie

Re: Do OEM main bearings have date codes?
 

I'll check mine tomorrow. I know they were original.

Re: Do OEM main bearings have date codes?
 

Those look to be original. Here are my original bearing numbers:
Front main bearings: (A) in circle, 55084 GMM 400 15C9. Other half: (A) 63377 GMM 400 16C9 0006

Rear bearing:57798(B)GMMA 295Q8 other half: 57799 (B) GMMA 001 3H9

Rod bearing: (B)GM AT-20 P-16 10 68 other half: (B) GM AT-20 P-44 12 68

So yes, they are date coded and original.

Re: Do OEM main bearings have date codes?
 

Thanks for taking the time to check your parts!

So it looks like my bearings are dated from '68... which is what I was hoping. Sure do enjoy seeing and learning more details about original parts....

Thanks again! Charlie