SPUN ROD BEARING! WHAT DO I DO!!!
 

Hi everyone Im brand new to this forum, This is my first post.
So I have a 1976, W115, 300D. The problem is when i bought it from some dumb kid who got it from his grandmother and did not take care of it, he managed to spin a rod bearing from running with no/low oil-_- So its number 2 bearing that spun, She still ran like a dream (not driven) started easily ideled smooth also the oil pressure was even all the way to the top, but had a terrible knock, Here is a vid to hear her:)


Pulled out the engine and trans took out the crank and The journal on num 2 looks pretty bad, definitely going to have to be ground but the others are in really good condition from what I see. Just took the crank to a machinist yesterday haven't heard back yet. So I will need oversized bearings right? or should i get a new crank. If so for wich ever one. Where can i get oversized bearings for this engine i cant find any just the standard 52.00, and if i need a crank, WHO HAS ONE! I reeally need this car done Im only 18 and took on this project knowing it was going to take some work im finishing high school early and I want to star school asap and need her done, it saddens me seeing her sitting in the driveway PLEASE TRY TO RESPOND ASAP Ill post pics of the bearing and the crank when i get it back

ok, Welcome to the forum!
now members can see your post, and comment on it.

Might want to have the crank built up and machined to an available bearing size. Thats if the maximum available oversize is not enough.

I have a set of Glyco oversized bearings 50.00 mm. Glyco 71-3227


I also have a N/A crank.

PM me if interested.

NUMBER 2 (the spun one) and another one to compare.

I would get a good used STD crank with flex disk.
Any 617 NA crank will work.
You also have to replace the connecting rod.

Where can i get a crank and a connecting rod? Damn i should have know it was going to be harder than just grinding polishing putt back and start like my dad made it sound-_-

My first bit of advice is

Don't panic!

Look you've done all you can do for now - you've taken the crank to a machine shop. They should be able to measure it up for you. They should be able to check for ovality and taper too. This is a test for them. If they don't know how to do that then you need to pick up your crank and leave!

Wait until you've got some advice from the machine shop before you seriously start to think about buying cranks.

Now some people (like myself) would then be looking for more trouble - I'd strip down the whole engine and make sure that everything else was perfect. However, I understand that that isn't what everyone would do. If you are planning to just fix the knock then - yes - it could be as simple as just replacing the bearing like your Dad said.

But like 1960mog says it is worthwhile checking out the condition of the connecting rod too.

I assume you've not removed the head yet and that you are only investigating from below?

X2
This is very good advice !!!
Dont be in a hurry to do anything. When the shop gets back to you, let us know what they have said & we will be happy to add our 2c worth.

By the way, welcome to the forum. Another 40 years & you will be able to advise some young guys on what to do in this situation !!
There are several ways forward for you. The cheapest may end up being a good second hand motor.
We will all just have to wait a while & see what the shop says.

Good Luck !!

As Army said, don't panic. Just wait and listen to what the machinist learns about it. If he says he can grind it, grind it. If he can't then find another crank.

Things like this are repaired in zillions of different engines on a regular basis. You already have half of the project finished in the tear down.

Good luck with it.

Answer
 

Post #4.

LOL,
Well, Whunter is up to his old electron saving ways again.... well done Roy.
If Deliveryvalve is indicating that that crank has been prepped and fits those bearings he has.... that is sure the way I would go given the situation described so far...

^^^ The crank is not fitted for the 50mm bearings. It is in original used condition fitted for 52mm bearings. The crank needs a little polishing, but should clean up well.

To the OP, the oversized bearing I have (50mm) is I think the biggest oversize you can get and allows for plenty of material to be machined off the crank. As you know, they are not really available anywhere. Your machine shop will determine the maximum that can be allowed to grind. You will need to have the shop inspect the connecting rod for serviceability. Spun bearings is not the end all on a connecting rod if physically it looks good, it can check out to be fine at the shop with further measurements.




.