MGB & GT Forum

Please Sign In or Register to Search

Rod Bearing Replacement - 1975 MGB

Posted by SSGt Olivero 
Save up to 15% with Moss Motors' Buy More, Save More Sale
AutoShrine Sponsor
AutoShrine Sponsor
AutoShrine Sponsor
AutoShrine Sponsor

SSGt Olivero Avatar
Eric Olivero
Montgomery, TX, USA   usa
1975 MG MGB "Julia"
1975 MG MGB

I have spent a lot of time reading postings in the MGB Forum and haven't found a thread on procedures for replacing rod bearings. I have discovered a lot of reasons why to do replace the bearings, but not so much on how. From what I understand, it is possible to replace the rod bearings and main bearing from under the engine. I have NEVER done this before, so I have a lot of questions and concerns before I start.

What I have done so far:
1) Removed the oil pan. Thanks for the postings on how to remove the front 4 bolts = PITA!
2) Removed the oil pump and cheked the lobe clearance, etc. The pump checks out good.
3) Gotten plenty of oil drips onto my face

Questions:
1) What Rod Bearing Set do I need for a 5 Main? (.010 / .020 / .030 / .040) How do I figure this out?
2) Do I also replace the Main Bearing? Size?
3) Will I need any special tools?
4) Are there any video postings that I can view to give me perspective and guidance?
5) Anything else I need to know?

balloonfoot Avatar
Lloyd Faust
Southlake, TEXAS, USA   usa

take a rod cap off and read the bearing size on the back size. That is the size you need. Only special tool is a torque wrench to do up the nuts when you put the cap back on.



“Better to remain silent and be thought a fool than to speak out and remove all doubt”.
- Abraham Lincoln

"Anyone with an intense emotional interest in a subject loses the ability to observe it objectively: You selectively perceive events. You ignore data and facts that disagree with your main philosophy. Even your memory works to fool you, as you selectively retain what you believe in, and subtly mask any memories that might conflict."

SSGt Olivero Avatar
Eric Olivero
Montgomery, TX, USA   usa
1975 MG MGB "Julia"
1975 MG MGB

So I have to take it apart first to figure out the size. So much for doing it all at once. It would be nice to have the parts I need first to be able to do it all in one session.
I'm still confused on how to do it. Every video I watch, the engine is out of the car and the replacement is done from the top.

. You can hide this ad & support the site by upgrading to a Gold Membership ~ click here for more info
balloonfoot Avatar
Lloyd Faust
Southlake, TEXAS, USA   usa

Eric...if you already have the pan off....it will take you two minutes to remove a rod cap. Tha's all you do...you don't take the rod/piston assy out of the engine. Just crawl underneath and take on cap off. Slide the bearing shell out of the cap and read the size on the abck size. Report back.



“Better to remain silent and be thought a fool than to speak out and remove all doubt”.
- Abraham Lincoln

"Anyone with an intense emotional interest in a subject loses the ability to observe it objectively: You selectively perceive events. You ignore data and facts that disagree with your main philosophy. Even your memory works to fool you, as you selectively retain what you believe in, and subtly mask any memories that might conflict."

chris Avatar
Chris Roop
Pendleton, OR, USA   usa

Adding to what Lloyd said, it is helpful to have the rod that you want to remove the cap from in the down position. Remove the cap. Put rubber hose over the rod bolts. Push the rod up and retrieve the other half of the bearing shell. The reason for the hose is to keep the rod bolt from banging on the crank journal and scarring it. Do this operation one rod at a time. Remove shells, replace shells, retorque rod caps. Move to next rod.
I don't replace some main bearings ie the 3 in the middle, because of a phobia about fluids taking the path of least resistance. By replacing just the 3 inner bearings, that would mean oil is really running out of the front and rear mains. I'm probably being a schmuck on this one as others have done it successfully. Mains don't wear at the same rate as rods though.


Member Services:
Check out the Vendor Market page for ever changing specials. Quality new parts at 15% off of list. No sales tax in Oregon. Not just for MG parts.
58twincam Avatar
Charlie K
Allentown, USA   usa

Eric, you did not say why you want/think you need to replace the crank bearings. Are you experiencing low oil pressure, knocking noises, or do you just want to replace them. There is more to it than just taking out the old bearing shells and replacing them. There are other things to consider, such as what is the condition of the crankshaft journals ( are they smooth and shiny or do they have lines in them or grooves). The journals should also be checked for concentricity. Then you have to consider how much wear the journal has expierienced and calculate the oil clearance between the journal and the bearing with plastigauge. If you think that the oil pressure has been ok and the bearings are not knocking then I would leave them alone. If you mess something up you will end up with a complete rebuild $$$$.

. You can hide this ad & support the site by upgrading to a Gold Membership ~ click here for more info
SSGt Olivero Avatar
Eric Olivero
Montgomery, TX, USA   usa
1975 MG MGB "Julia"
1975 MG MGB

I will have to start fresh in the morning. Wife just left to the store and I now have a grumpy 3 year old to kep me busy.

Once I take off ONE cap and determine the size, will each rod bearing be the exact same size for every connecting rod?

balloonfoot Avatar
Lloyd Faust
Southlake, TEXAS, USA   usa

yup



“Better to remain silent and be thought a fool than to speak out and remove all doubt”.
- Abraham Lincoln

"Anyone with an intense emotional interest in a subject loses the ability to observe it objectively: You selectively perceive events. You ignore data and facts that disagree with your main philosophy. Even your memory works to fool you, as you selectively retain what you believe in, and subtly mask any memories that might conflict."

. You can hide this ad & support the site by upgrading to a Gold Membership ~ click here for more info
chris Avatar
Chris Roop
Pendleton, OR, USA   usa

Yes, but listen to 58twincam below. He makes a couple of exelent points.


Member Services:
Check out the Vendor Market page for ever changing specials. Quality new parts at 15% off of list. No sales tax in Oregon. Not just for MG parts.
Ken Plumstead Avatar
Smithers, B.C., Canada   can
1965 MG MGB

One quick note; Whether removing one or all bearing caps make sure they go back in the same place and the same orientation. Do not mix them up.

Ken



MGB: Transforming gasoline into Fun!!!

SSGt Olivero Avatar
Eric Olivero
Montgomery, TX, USA   usa
1975 MG MGB "Julia"
1975 MG MGB

Okay - I took of one cap, noted the orientation of the cap. I have the both sides of the bearings on my workbench. I see nothing that indicates size. What now?

dickmoritz Avatar
Dick Moritz
Philly 'burbs, PA, USA   usa

Eric,

Look at the back of the shells. They'll say "STD," ".010," etc., or they'll just have a part number with no size indicated, in which case they're standard...

Dick



Errabundi Saepe, Semper Certi
(Often wrong, but always certain)

SSGt Olivero Avatar
Eric Olivero
Montgomery, TX, USA   usa
1975 MG MGB "Julia"
1975 MG MGB

So what if I don't see anything at all? Does that mean just STANDARD?

SSGt Olivero Avatar
Eric Olivero
Montgomery, TX, USA   usa
1975 MG MGB "Julia"
1975 MG MGB

I took off each cap, one at a time, replaced the caps after removing the bearings. Now I know the caps are in the same position and orientation.
The only markings I could find on the back of the bearings:
A makers stamp - 5116
The other side - 12H2719
I'm assuming these numbers are part numbers for the manufacturer.

Now to order the parts:

Connecting Rod Bearing Set, std. (5 Main)- MOSS = $28.95 / BHive = Tri-Metal = $46.90 / O'Rielly = Beck/Arnley = $47.99
I have a few other parts I need too. I prefer to get them all at once and save on shipping.
I like dealing with Gordan at BHive, but Moss is great too. I use O'Rielly whenever I need basic stuff. Not too sure what product is going to be the better quality.

Overall, for the other parts I need, BHive has the best prices. I will most likely by everything from Gordon. UNLESS someone can tell me why I shouldn't buy the TRI-METAL bearing set.
Since I'm at it - replace the oil filter and pick a new oil. I could read the forums for MONTHS to get advice on oil filters and oil types. I think I will keep this to myself, I wouldn't want to start a controversy.

In the end - replacing the connecting rod bearings hasn't been that hard. I was nervous at first, but thanks for all the help! I will post more results once I get my parts in.



Edited 1 time(s). Last edit at 2012-08-05 10:36 AM by SSGt Olivero.

dickmoritz Avatar
Dick Moritz
Philly 'burbs, PA, USA   usa

Eric,

As noted earlier, no size marking means standard size. You'd be remiss if you didn't at least pull down the second and fourth main bearing caps to examine the bearings, and with a little finagling, you can also pull down the center cap, although it will be a bit tighter than the others. Note that the center main cap also houses the thrust washers, that just sit in place.
The only thing you need to remember about the thrust washers is that the grooves for oil face outward, toward the ends of the block, not inward toward each other. Suggest you post photos of your rod bearing shells, as well as photos of the number two and four main bearing shells, since you now have the opportunity to replace three out of the five pairs of main bearings, which is little additional work or cost as long as you're in there...

Dick



Errabundi Saepe, Semper Certi
(Often wrong, but always certain)

. You can hide this ad & support the site by upgrading to a Gold Membership ~ click here for more info

To add your reply, or post your own questions

Members Sign In   or   Create an Account

Registration is FREE and takes less than a minute!

Having trouble posting or changing forum settings?
Check the Forum Help File (FAQ) or contact the webmaster.


Join The Club

Sign in to ask questions, share photos, and access all website features

MGExp Menu

What's New

Membership

Forums ->

MGB & GT

MG Midget

Buy, Sell & Trade

Vendor Market

MG Engine Swaps

Original MG

MGA

MGC

MG Magnette

1100 & 1300

T-Series & Prewar

Modern MGs

MG Motorsports

Member Meetup

MG 2015 Event

Other Vehicles

Off Topic

Clubs

Forum Search

Random Topic

Latest Posts

Live Chat

Calendar

Journals

Tech Library

Car Registry

Cars For Sale

Model Info

Motorsport

Directory

Member Map

MGExp Store

Search Site

Advertising Info

Smartphone quick link
mgexp.mobi

Adjust Text Size

Larger Smaller
Reset Save