Rod Bearing Size - oversize ?
Thread Starter
Instructor
Joined: Apr 2004
Posts: 166
Likes: 4
From: Moneta, VA
Rod Bearing Size - oversize ?
Hi,
I am in the process of freshing up my block on an 89 350.
The original GM Rod bearings are marked 013 OS
I measure the journal at 2.099", the worn bearings at 2.102" ID and the rod end at 2.225" OD
From the Clevite 77 Catalog the standard bearing shells are 0.062 thick.
This adds up to a 0.002 clearance with standard sizes.
I'm I figuring this correctly? It looks like I just need STD rod bearings.
What's up with the 013 OS stamped size?
thanks in advance for the help?
I am in the process of freshing up my block on an 89 350.
The original GM Rod bearings are marked 013 OS
I measure the journal at 2.099", the worn bearings at 2.102" ID and the rod end at 2.225" OD
From the Clevite 77 Catalog the standard bearing shells are 0.062 thick.
This adds up to a 0.002 clearance with standard sizes.
I'm I figuring this correctly? It looks like I just need STD rod bearings.
What's up with the 013 OS stamped size?
thanks in advance for the help?
Former Vendor
Joined: Jun 2001
Posts: 7,204
Likes: 6
From: St Marys PA
Oversized are if you need to have your crank ground .010. You can usually get a few grinds done to the crank if it should spin a bearing or something that mars the cranks surface. Wish that is all I needed to do with mine. 
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Are you measuring the I.D. of the bearings installed in the rods with the caps torqued? My math says, 2.102" - 2.099" = 0.003". My Helms calls for the rod bearing clearance to be 0.0013" to 0.0035". The crank journal should measure between 2.0988" and 2.0998. The bore in the rod, 2.2247" to 2.2252". I have no clue what the ".013 OS" stands for, but with your "standard" crank, a .013" or even a .010" bearing would lock that engine up tighter than (fill in your favorite simile). Depending too much on book specs can get you in trouble. I agree that standard bearings are what you probably need. Install some standards in the rods and measure the I.D. and subtract that from the journal diameter. If your measuring devices aren't all that accurate, plastigage is a good alternative. Depending on what you see, and what are going to use the engine for, a set of 0.001" might be desirable.
RACE ON!!!
RACE ON!!!
Racer
Joined: Nov 2005
Posts: 456
Likes: 3
From: Sumner Texas
As CFI said the OS does NOT stand for oversize. To begin with bearings don't come in "oversize." When you turn the crank the journals become smaller requiring UNDERSIZE bearings.
As CFI described, measure carefully and inspect the journals. You most likely can go back with standard size bearings.
Good luck,
As CFI described, measure carefully and inspect the journals. You most likely can go back with standard size bearings.
Good luck,
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by MBDiagMan
To begin with bearings don't come in "oversize." When you turn the crank the journals become smaller requiring UNDERSIZE bearings.
RACE ON!!!
Racer
Joined: Nov 2005
Posts: 456
Likes: 3
From: Sumner Texas
Originally Posted by CFI-EFI
When the shaft journals are turned, undersized, an over sized bearing is needed to fill the void the grinding created. The bearing for an undersized journal is thicker, or over sized.
RACE ON!!!
RACE ON!!!
The industry term relates to the size of the journal which becomes undersize from the machine operation.
As a quick example of the industry standard term:
http://engineparts.com/motorhead/techstuff/clrcode.html
Have a great day,
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by MBDiagMan
Yes, if you choose to come up with a way to justify the use of the term oversize, the thicker bearing would indeed justify the term oversize.
RACE ON!!!
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Every 2027 Corvette Engine Explained
Joe Kucinski
Designer Imagines A Corvette That Looks More Like a Corvette Than the Corvette
Verdad Gallardo
10 Ugly Corvettes That We Still Kinda Love
Joe Kucinski
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Racer
Joined: Nov 2005
Posts: 456
Likes: 3
From: Sumner Texas
Now look at who's scanning posts instead of reading them carefully? I did not jump onto ski. I merely wanted him to know the difference so he would know the difference when he goes to buy bearings.
I've been buying engine bearings for over 40 years and I've never heard of an oversize rod or main bearing. That would indicate that there is such a thing as an oversized rod or main journal.
I've offered a truce before and you still haven't accepted. How about now? We can agree to just stop picking at each other and enjoy our cars and learn from each other. I sense that I can learn a lot from you and I may not be very smart, but I've been wrenching long enough that there must be something, somewhere that you can learn from me.
Peace,
I've been buying engine bearings for over 40 years and I've never heard of an oversize rod or main bearing. That would indicate that there is such a thing as an oversized rod or main journal.
I've offered a truce before and you still haven't accepted. How about now? We can agree to just stop picking at each other and enjoy our cars and learn from each other. I sense that I can learn a lot from you and I may not be very smart, but I've been wrenching long enough that there must be something, somewhere that you can learn from me.
Peace,
Former Vendor
Joined: Jun 2001
Posts: 7,204
Likes: 6
From: St Marys PA
Well not sure what the terminology industrial standard is with bearings, but I have always heard bearings that are used for turned crankshafts referred to as "oversized"
Oversized in the sense they are "thicker" with the same OD size. Hence making up the difference the crank has been turned. I guess we never really questions one another in the use of the terminology since we all knew what we were trying to say. You right though they should be reffered to as undersized.
This is also why I highly suggest and I always buy my bearings from the guy that does our machining. I always double check clearances, but he has yet to let me down.
As for clearances, I would shoot for around .003 and .0035 on the high side.
Oversized in the sense they are "thicker" with the same OD size. Hence making up the difference the crank has been turned. I guess we never really questions one another in the use of the terminology since we all knew what we were trying to say. You right though they should be reffered to as undersized.
This is also why I highly suggest and I always buy my bearings from the guy that does our machining. I always double check clearances, but he has yet to let me down.
As for clearances, I would shoot for around .003 and .0035 on the high side.
Thread Starter
Instructor
Joined: Apr 2004
Posts: 166
Likes: 4
From: Moneta, VA
just for the record
Clevite Catalog lists a rod bearing CB-1776P-10 that is for a "Rod Housing Bore Resized 0.002" larger than stock".
This bearing is available in for 20, 30, 40 thousands undersized journals.
So if I've got the terminology right, you can have an oversized bearing (housing) that is also undersized (journal).
Anyway thanks for the feedback on the bearing sizing, It looks like standard is the right size.
Clevite Catalog lists a rod bearing CB-1776P-10 that is for a "Rod Housing Bore Resized 0.002" larger than stock".
This bearing is available in for 20, 30, 40 thousands undersized journals.
So if I've got the terminology right, you can have an oversized bearing (housing) that is also undersized (journal).
Anyway thanks for the feedback on the bearing sizing, It looks like standard is the right size.
1st Gear
Joined: Nov 2022
Posts: 1
Likes: 0
Hi,
I am in the process of freshing up my block on an 89 350.
The original GM Rod bearings are marked 013 OS
I measure the journal at 2.099", the worn bearings at 2.102" ID and the rod end at 2.225" OD
From the Clevite 77 Catalog the standard bearing shells are 0.062 thick.
This adds up to a 0.002 clearance with standard sizes.
I'm I figuring this correctly? It looks like I just need STD rod bearings.
What's up with the 013 OS stamped size?
thanks in advance for the help?
I am in the process of freshing up my block on an 89 350.
The original GM Rod bearings are marked 013 OS
I measure the journal at 2.099", the worn bearings at 2.102" ID and the rod end at 2.225" OD
From the Clevite 77 Catalog the standard bearing shells are 0.062 thick.
This adds up to a 0.002 clearance with standard sizes.
I'm I figuring this correctly? It looks like I just need STD rod bearings.
What's up with the 013 OS stamped size?
thanks in advance for the help?
this means 13/1000” over sized big end bore on the rod.
I did mic the id of rod bore, it was beyond the standard size.
of cause std size bearing on the rod means very loose clearance.
I think no after market over sized (bore side) bearing anyway.
Last edited by rust samurai; Nov 23, 2022 at 06:44 PM.
